# Driveline angle????



## NoGoat (Jul 21, 2021)

Hey y'all. So I have a vibration that starts at around 60mph. Pretty sure it's driveline angle related.
-67 LeMans
-77 400ci
-th400
-GM 10 bolt rear
Here are my angles:
Trans 4.1* down towards rear
Driveshaft 1.3* down towards rear
Pinion .5* up towards front
Operating angle 1 is 2.8*
Operating angle 2 is 0.8*

When I swapped the trans from the 2speed to the th400, I just used the same cross member and moved it rearward. Is there a specific X member for th400?

The fan is already low in the shroud, so don't think I should raise the tail of the trans. So I guess adjustable upper control arms?

Why if all this was a combination of parts from the factory (GTO at least) is it that far off?


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## armyadarkness (Dec 7, 2020)

Im not the drive angle expert, but I'm not following how control arms could affect it. I assume that you've already verified your ujoints to be good, and greased? Is this a new vibration or has it always been there?


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## Sick467 (Oct 29, 2019)

Like Army, I'm no whizbang with drive angles.

You can see vibrations like you are if your slip yoke is positioned too far to the rear. Meaning it is not inserted into the transmission enough.

It also appears that if you try to get your operating angles equal to each other (the closer to each other the better and between 1° and 3°, some u-joints can handle as much as 7°) by raising the rear of the transmission, the drive shaft angle would change making the pinion-to-shaft angle even less. It seems like it would be chasing the angles back not necessarliy getting them to converge upon each other. My thought is that the trans and rear diff need slight adjustments. Having to change the rear-end angle does not make alot of sense to me...hopefully it's more simple than I imagine!


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## O52 (Jan 27, 2019)

I used UMI adjustable rear upper control arms to solve a vibration problem in my El Camino. 









1968-1972 GM A-Body Adjustable Rear Upper Control Arms- Roto-Joints - UMI Performance Inc.


UMI’s Roto-Joint adjustable rear upper control arms are a bulletproof addition to your street or pro-touring car. UMI’s Roto-Joint upper




www.umiperformance.com










Upper Rear Control Arms Archives - UMI Performance Inc.







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There are numerous transmission mounts available. Most of them are too tall. I found this shorter one to solve radiator shroud to fan clearance issues with the 396/T400


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## armyadarkness (Dec 7, 2020)

Now I see what he meant by adjustable control arms. My only opinion there is that unless it's happening to everyone, then something else is likely the culprit. 

Since a trans swap was involved, I'd look at the crossmember. There are many creative approaches when looking at them. On my old Blazer, you could drop the CM below the frame and even use spacers to drop it further. 

Also, if your avatar is your car, it looks lowered. If that's true, then youd definitely be aggravating your pinion angle. In that case, those UMI upper arms would be the cure.


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## O52 (Jan 27, 2019)

With the adjustable upper arms you can move the pinon up and down or even move the axle ends back and forth.


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## NoGoat (Jul 21, 2021)

armyadarkness said:


> Now I see what he meant by adjustable control arms. My only opinion there is that unless it's happening to everyone, then something else is likely the culprit.
> 
> Since a trans swap was involved, I'd look at the crossmember. There are many creative approaches when looking at them. On my old Blazer, you could drop the CM below the frame and even use spacers to drop it further.
> 
> Also, if your avatar is your car, it looks lowered. If that's true, then youd definitely be aggravating your pinion angle. In that case, those UMI upper arms would be the cure.


Technically it’s not lowered. Years and years ago I redid the suspension including springs. The front sat too high compared to the rear so I clamped the front an inch or so. Sits right at original ride height based on what I’ve researched.


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## PontiacJim (Dec 29, 2012)

NoGoat said:


> Hey y'all. So I have a vibration that starts at around 60mph. Pretty sure it's driveline angle related.
> -67 LeMans
> -77 400ci
> -th400
> ...



Here are some notes on the TKO-600 trans with regards to driveshaft angles.

Both the transmission output shaft (which includes the entire crank centerline of the engine) and rear end pinion should both be on the same angle (parallel, or as close as possible). The u-joints should have an EQUAL (within 1degree) AND OPPOSITE (to each other) ANGLE of no more than 3.5 degrees. This is a perfect world setting, but we all know that's not always achievable. The closer you can get to these specifications the longer your u-joints will last. The farther from these settings you go, the lifespan of the u-joints is reduced and the possibility of vibration associated with them increases. This does not mean that you will have a vibration that you can feel if you are not right on these specs. The goal should be to get as close as you can. U-joints MUST have at least a ½ degree angle to operate. A u-joint that is zero angled will not last very long. There are a lot of modified cars on the road with less than desirable u-joint angles and they run with no noticeable vibration but their lifespan will be shortened. Another thing to consider is spring wrap which is a very important thing to consider when diagnosing a vibration problem. There have been a lot of people who have incorrectly diagnosed a driveshaft vibration and have blamed the driveshaft when it isn't the problem at all. When accelerating and decelerating the pinion angle changes. When accelerating the pinion goes up, when decelerating the pinion goes down. This changes the ujoint angle drastically, especially at the rear. If your springs are weak or if you have a lot of horsepower with good traction, this can be a real problem because as the angle increases beyond acceptable limits the vibration gets worse. Try to get your angles as close as you can then worry about stabilizing the rear end if it becomes an issue. 

The engine is positioned from the factory at an angle. If you change things, you want to try and keep the engine angle the same as this will mean the trans angle is not correct. Installing aftermarket engine/trans mounts, or new rubber ends on the trans crossmember or not correctly installing them, or even a bent crossmember can throw things off.

For 1967, the angle of the engine is listed as 4 degrees 42 minutes - so you are not that far off on the back of the trans.

So that would seem that the engine/trans is where you want it to be. So your issue looks to be at the rear end. Is it an original Pontiac 10-bolt that the car was born with? Bad bushings, weak springs (or jacked up rear-end), incorrect control arms or something bent.

So if you apply the above info with regards to driveshaft angles, you want the rear pinion angle to be almost the same as the front. If I am understanding your numbers, the trans angle is 4.1 degrees and the driveshaft at the front u-jount has a 1.3 degree angle. At the rear end, the pinion angle is .5 degrees up.

I am no expert on any of this, but my thinking is that the 4.1 angle on the back of the trans needs to match a like 4.1 angle up on the pinion. This will be a 0 difference in angularity between the trans and pinion yoke. Once that is gotten, I believe the driveshaft angles should be the same and then adjust from there, Mark Williams states for drag racing, no more than 2 degrees, but at least .5 degrees.

The car has to be set on the ground with its weight on it. Same goes with tightening the rear end control arm bushings - if new ones were installed. If not, done while on the ground with car's weight, it can preload the rubber bushings and you will not get an accurate result.

2 drawing included that may help.


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## NoGoat (Jul 21, 2021)

PontiacJim said:


> Here are some notes on the TKO-600 trans with regards to driveshaft angles.
> 
> Both the transmission output shaft (which includes the entire crank centerline of the engine) and rear end pinion should both be on the same angle (parallel, or as close as possible). The u-joints should have an EQUAL (within 1degree) AND OPPOSITE (to each other) ANGLE of no more than 3.5 degrees. This is a perfect world setting, but we all know that's not always achievable. The closer you can get to these specifications the longer your u-joints will last. The farther from these settings you go, the lifespan of the u-joints is reduced and the possibility of vibration associated with them increases. This does not mean that you will have a vibration that you can feel if you are not right on these specs. The goal should be to get as close as you can. U-joints MUST have at least a ½ degree angle to operate. A u-joint that is zero angled will not last very long. There are a lot of modified cars on the road with less than desirable u-joint angles and they run with no noticeable vibration but their lifespan will be shortened. Another thing to consider is spring wrap which is a very important thing to consider when diagnosing a vibration problem. There have been a lot of people who have incorrectly diagnosed a driveshaft vibration and have blamed the driveshaft when it isn't the problem at all. When accelerating and decelerating the pinion angle changes. When accelerating the pinion goes up, when decelerating the pinion goes down. This changes the ujoint angle drastically, especially at the rear. If your springs are weak or if you have a lot of horsepower with good traction, this can be a real problem because as the angle increases beyond acceptable limits the vibration gets worse. Try to get your angles as close as you can then worry about stabilizing the rear end if it becomes an issue.
> 
> ...


Jim you are a treasure. Thank you for taking the time to help with such detail.

Glad to hear that the engine and transmission are close to where they should be. No, the rear is not original to the car. It is a BOP of similar vintage, but I don’t know the details. I’ll crawl under there and check it out. New bushings in upper, new boxed lowers. So I understand what needs to happen, not sure how to achieve it.
Thanks again for the input.


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## Autie1969GTO (Mar 5, 2019)

I did the same swap from a 2 speed to a TH400 on my 66 back in 1987. It has factory spec convertible rear springs w/2" blocks and open stock control arms. The only issue I had was, I needed to have the driveshaft shortened/re-balanced (I do not remember how much) because it was a tight fit with no "play/clearance" to allow for rear axle travel. I am almost positive I still utilized the 2 speed trans mount. I know 100% I did still use the same factory cross member, but I seem to recall relocating it either forward or back a little (some of the finer details are hard to remember after 30+ years). I do know for sure that no other major alterations were made. My fan sits directly in the middle of the factory shroud. It never moved up or down after the swap. Never had a problem and still "chirps" into 2nd gear. The "key" is when did it start?? Did the vibration start immediately after you made the swap, did it start gradually and get worse OR started immediately with no build up soon after you made the swap? Any new tires/wheels been added? Did you check and see if possibly a wheel weight came off a wheel? Happened to me once causing vibration. Depending on when it started, If the driveshaft pitch is sufficient and there is enough play/clearance in the driveshaft and it is balanced, and the vibration started a little after the swap, I would have the tires re-balanced and check front suspension/steering. Hope this helps


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## NoGoat (Jul 21, 2021)

Autie1969GTO said:


> I did the same swap from a 2 speed to a TH400 on my 66 back in 1987. It has factory spec convertible rear springs w/2" blocks and open stock control arms. The only issue I had was, I needed to have the driveshaft shortened/re-balanced (I do not remember how much) because it was a tight fit with no "play/clearance" to allow for rear axle travel. I am almost positive I still utilized the 2 speed trans mount. I know 100% I did still use the same factory cross member, but I seem to recall relocating it either forward or back a little (some of the finer details are hard to remember after 30+ years). I do know for sure that no other major alterations were made. My fan sits directly in the middle of the factory shroud. It never moved up or down after the swap. Never had a problem and still "chirps" into 2nd gear. The "key" is when did it start?? Did the vibration start immediately after you made the swap, did it start gradually and get worse OR started immediately with no build up soon after you made the swap? Any new tires/wheels been added? Did you check and see if possibly a wheel weight came off a wheel? Happened to me once causing vibration. Depending on when it started, If the driveshaft pitch is sufficient and there is enough play/clearance in the driveshaft and it is balanced, and the vibration started a little after the swap, I would have the tires re-balanced and check front suspension/steering. Hope this helps


Yes, thank you. For as relatively simple as these car are, there are always many variables to check.

I swapped the transmission and the rear end at the same time 20 years ago. It did start after that, so could be anything related to both of them. The reason I don't think it's wheel related is it smooth until 60 mph. I would expect the wheel out of balance would vibrate starting at a lower speed and get worse as I go faster.


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## NoGoat (Jul 21, 2021)

I should have mentioned this in the original post / question. 2 years ago the torque converter "blew up". The trans needed to be rebuild due to all the shrapnel that went through it. The vibration was worse before the rebuild. After the rebuild it is about half as intense as before. 

Not sure if that will help with any diagnosis.


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## michaelfind (Dec 14, 2018)

armyadarkness said:


> Now I see what he meant by adjustable control arms. My only opinion there is that unless it's happening to everyone, then something else is likely the culprit.
> 
> Since a trans swap was involved, I'd look at the crossmember. There are many creative approaches when looking at them. On my old Blazer, you could drop the CM below the frame and even use spacers to drop it further.
> 
> Also, if your avatar is your car, it looks lowered. If that's true, then youd definitely be aggravating your pinion angle. In that case, those UMI upper arms would be the cure.


I had the same problem except it started around 50mph for me. The adjustable upper control arms fixed the problem for me and supposedly gave me better traction. My tires are too small and Lemans Guy helped me get too much torque out of my motor so I'll never get good traction.


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## michaelfind (Dec 14, 2018)

NoGoat said:


> Jim you are a treasure. Thank you for taking the time to help with such detail.
> 
> Glad to hear that the engine and transmission are close to where they should be. No, the rear is not original to the car. It is a BOP of similar vintage, but I don’t know the details. I’ll crawl under there and check it out. New bushings in upper, new boxed lowers. So I understand what needs to happen, not sure how to achieve it.
> Thanks again for the input.


And, like you, my vibration started after I installed the new boxed lower control arms. I can't explain why, but that is what happened.


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## NoGoat (Jul 21, 2021)

michaelfind said:


> I had the same problem except it started around 50mph for me. The adjustable upper control arms fixed the problem for me and supposedly gave me better traction. My tires are too small and Lemans Guy helped me get too much torque out of my motor so I'll never get good traction.


Thanks for the input. Way to go Lemans Guy!


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## NoGoat (Jul 21, 2021)

michaelfind said:


> And, like you, my vibration started after I installed the new boxed lower control arms. I can't explain why, but that is what happened.


Which upper adjustable arms did you get?


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## michaelfind (Dec 14, 2018)

NoGoat said:


> Which upper adjustable arms did you get?


I think I ended up buying UMI through Summit. I shopped prices for so long, I forgot which ones I actually ordered. I also think there was a detail about the year of the rear end that made a difference. Mine is out of a 69 and is mounted in my 65. I think there was some difference about the rears that happened in mid or late 60s, but don't recall right now what that was. I think that if you identify the year of the rear end you have and purchase based on that information, you should not have problems. Anyone else know more about this? Please jump in so I don't mislead him.


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## Autie1969GTO (Mar 5, 2019)

NoGoat said:


> I should have mentioned this in the original post / question. 2 years ago the torque converter "blew up". The trans needed to be rebuild due to all the shrapnel that went through it. The vibration was worse before the rebuild. After the rebuild it is about half as intense as before.
> 
> Not sure if that will help with any diagnosis.


The vibration started immediately AFTER you made the swap and lessened, but still there after the rebuild? Did you replace the control arms the same time as the trans swap? Did anyone check for hairline crack in the housing where the torque converter slips in? Also check around and on the top of the trans tail housing where the yoke slips into for hairline crack. The flywheel wasn't hit/possibly damaged during the swap? Process of elimination.


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## Honeyharbour62 (Jul 15, 2018)

My vibration comes in at 3k regardless of what gear I'm in and goes away when I put the clutch in. Engine. I sincerely hope that's not your problem.


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## 66COUPE (Jul 23, 2021)

Honeyharbour62 said:


> My vibration comes in at 3k regardless of what gear I'm in and goes away when I put the clutch in. Engine. I sincerely hope that's not your problem.


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## armyadarkness (Dec 7, 2020)

NoGoat said:


> Technically it’s not lowered. Years and years ago I redid the suspension including springs. The front sat too high compared to the rear so I clamped the front an inch or so. Sits right at original ride height based on what I’ve researched.
> View attachment 145150


Sweet car! Looks lowered in the avatar, but normal here. I use all Global West stuff on my car and I love it... Plus, it's made in the USA, so it's IN STOCK! It's pricey though


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## armyadarkness (Dec 7, 2020)

NoGoat said:


> Yes, thank you. For as relatively simple as these car are, there are always many variables to check.
> 
> I swapped the transmission and the rear end at the same time 20 years ago. It did start after that, so could be anything related to both of them. The reason I don't think it's wheel related is it smooth until 60 mph. I would expect the wheel out of balance would vibrate starting at a lower speed and get worse as I go faster.


An out of balance wheel would be a problem whenever it chose to be... 50 -60mph is usually the trouble area for them. If you're going to solve this, start with easy eliminations... try different wheels or rotation, if you have access


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## 66COUPE (Jul 23, 2021)

I’m new to the forum so still figuring it out, but 42 years of working on my 66 GTO, several years ago I replaced my old rotted/ melted engine mounts and figured I’d put in a new fancy hi tech racing trans mount as well on the old 2 speed, big mistake, it pushed the tail of the trans up to where the u joint was almost rubbing on the tunnel, I didn’t notice till the first test run getting on it a little up a freeway ramp there was increasing vibration and then the u joint started hitting the tunnel and that sound right next to the seat isn’t what you want to hear, drove like grandma back home and got a good old fashioned stock rubber mount for like $5 bucks and all good. Might be something that simple as keeping things stock.


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## NoGoat (Jul 21, 2021)

Honeyharbour62 said:


> My vibration comes in at 3k regardless of what gear I'm in and goes away when I put the clutch in. Engine. I sincerely hope that's not your problem.


No thank goodness. If I'm going 60, and put it in neutral and coast the vibration is still there.


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## NoGoat (Jul 21, 2021)

armyadarkness said:


> An out of balance wheel would be a problem whenever it chose to be... 50 -60mph is usually the trouble area for them. If you're going to solve this, start with easy eliminations... try different wheels or rotation, if you have access


I would agree except...After the trans was rebuild it got better, not gone but better. Maybe the vibration had slowly caused the bearings in the trans to wear and that's why it finally blew apart. I'm still confused as to why the trans and rear pinion angles are so off. As PJ stated, the engine and trans angle is very close to factory at 4.1*, but the rear is at 0.5*. The components, while not original to the car are correct to the architecture. Unless the rear ends had different mounting locations for 64-67 and 68-72. Does anyone know if that is true?


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## BearGFR (Aug 25, 2008)

Drive-line angles... It sounds harder than it is. What you're after is getting the centerline of the crank/transmission to be parallel to the centerline of the rear axle pinion, and you have to achieve this alignment in BOTH planes: up/down and side/side. Otherwise, one or both U-joints will tend to bind as they spin, and you'll get a vibration.

Here's a GREAT video that shows what happens when the centerlines aren't parallel.






Any time that there's any sort of angle "across" the driving and the driven side of a Cardan joint (cross type U-joint), the driven side of the joint does NOT spin at a constant speed(!). It will be continuously speeding up and slowing down slightly as it turns.

The only way to "cancel out" this oscillation in rotational speed is to have another Cardan joint at "the other end" of the system AND have the centerline of whatever is being driven at that spot be exactly parallel with the centerline of the original input. If the system is out of parallel, either up and down or side to side, then that speed oscillation won't be negated and whatever's being driven "at the other end" of the system will pick up a vibration.

In our cars (hopefully) the output of the transmission is mostly "fixed" and doesn't move, but that's not true of the rear axle. It has to move up and down with the action of the suspension so there's always going to be at least some angularity created in the drive shaft, and not only that but the amount of angle will change whenever the suspension moves. Plus, as the rear axle moves up and down the distance between it and the transmission also changes slightly. That's why there has to also be a slip joint in the system: to let the drive shaft get "slightly longer" or "slightly shorter" as the axle moves through its suspension travel.

So, whenever we make changes that "move something", like a transmission swap or even a different crossmember/rear trans mount we have to make sure that the centerline of the rear axle continues to be parallel to the centerline of the transmission. In the vertical plane (up and down) the way to do this is with adjustable UPPER control arms to 'tilt' the rear axle back into parallel. In the horizonal plane (side to side) adjustable LOWER control arms are used to "square up" the axle with the centerline of the transmission. Adjustable lowers also can be used to move the rear wheels forward or backward so that they're centered in the wheel wells, but they still have to be kept square with the transmission centerline.

Getting the up/down relationship isn't hard to do if you have adjustability and use a tool like one of these:
Competition Engineering C5020 Competition Engineering Angle Finder | Summit Racing
"Shoot angles" using the flat of the U-joint at the transmission slip joint (with it pointed straight "up") and also at the pinion yoke on the rear axle (also with it pointed straight up) and adjust the upper control arms (equal increments on both sides) until those angles are the same. 

Getting the side to side relationship is harder just because it's harder to measure accurately and determine when you've "got it".
One way is to support the car on a flat level surface and on its suspension (using jack stands for example, or on a 4-post lift), use a plumb bob at the front centerline of the crank and at the rear centerline of the transmission to make chalk marks on the floor, connect those two points with a chalk line, then use a square to draw a line "across" the floor that's at a perfect 90 degrees to the engine/transmission centerline. When the rear axle is square, the distance from that line to the axle flange centerline will be the same on both sides. If you have to make adjustments, be sure to take the weight off the rear wheels and let the axle "settle", then put the weight back on it and re-measure to make sure it's right.

One last note. If there's any "twist" at all in the drive shaft such that the Cardan joint crosses at both ends aren't perfectly lined up with each other, then you'll still get a vibration even if all the angles are perfectly aligned because the speed oscillations at each end will be "out of phase" with each other. 

So, things that can cause driveline vibrations:

Out of balance (the drive shaft itself or something attached to it, like one or both yokes)
Driveline angles (centerline of rear axle not parallel to centerline of engine/transmission)
Drive shaft twisted (Cardan joint crosses not square with each other)
Badly worn/sloppy bearings/bushings at the transmission output or rear axle input (perhaps caused/made worse by one of the above)
Bear


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## michaelfind (Dec 14, 2018)

NoGoat said:


> I would agree except...After the trans was rebuild it got better, not gone but better. Maybe the vibration had slowly caused the bearings in the trans to wear and that's why it finally blew apart. I'm still confused as to why the trans and rear pinion angles are so off. As PJ stated, the engine and trans angle is very close to factory at 4.1*, but the rear is at 0.5*. The components, while not original to the car are correct to the architecture. Unless the rear ends had different mounting locations for 64-67 and 68-72. Does anyone know if that is true?


Maybe it's the length of the upper arm that is different? Places like Spohn list different parts for 64-67 and 68-72. I suggest you call and ask a manufacturer or vendor what the difference is. I don't recall why, but I was advised to get the 68-72 part for my 69 ear end and it bolted in fine under my 65.


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## michaelfind (Dec 14, 2018)

NoGoat said:


> I would agree except...After the trans was rebuild it got better, not gone but better. Maybe the vibration had slowly caused the bearings in the trans to wear and that's why it finally blew apart. I'm still confused as to why the trans and rear pinion angles are so off. As PJ stated, the engine and trans angle is very close to factory at 4.1*, but the rear is at 0.5*. The components, while not original to the car are correct to the architecture. Unless the rear ends had different mounting locations for 64-67 and 68-72. Does anyone know if that is true?


Well, I'm sorry. I'm trying to figure out where I found that information and discovered I told you wrong. 
I installed the part corresponding to my car, not the rear end. I purchased UMI 4019 B and it worked for bolting a 69 ear end under a 65 and helped me eliminate the vibration I was having.

Now that I have discredited myself. I'll go search more for that difference in the parts.


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## NoGoat (Jul 21, 2021)

michaelfind said:


> Well, I'm sorry. I'm trying to figure out where I found that information and discovered I told you wrong.
> I installed the part corresponding to my car, not the rear end. I purchased UMI 4019 B and it worked for bolting a 69 ear end under a 65 and helped me eliminate the vibration I was having.
> 
> Now that I have discredited myself. I'll go search more for that difference in the parts.


All good Mike. The 64-67 vs 68-72 is quite different.


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## NoGoat (Jul 21, 2021)

BearGFR said:


> Drive-line angles... It sounds harder than it is. What you're after is getting the centerline of the crank/transmission to be parallel to the centerline of the rear axle pinion, and you have to achieve this alignment in BOTH planes: up/down and side/side. Otherwise, one or both U-joints will tend to bind as they spin, and you'll get a vibration.
> 
> Here's a GREAT video that shows what happens when the centerlines aren't parallel.
> 
> ...


As I said to JP, you guys are great for always helping out those of us not as experienced.
Thank you for such a detailed response.
It started after 3 things were changed at once...
1) 300 to th400 trans
2) 2.64 rear to 3.55 posi full swap not just innards
3) and drive shaft

I can NOT guarantee the drive shaft is true, but based on my angles it seems probable it's the rear pinion angle as the cause. Would you agree?
Trans = 4.1* down towards rear
Driveshaft = 1.3* up towards front
Rear pinion = 0.5* nose up towards front


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## armyadarkness (Dec 7, 2020)

NoGoat said:


> I would agree except...After the trans was rebuild it got better, not gone but better. Maybe the vibration had slowly caused the bearings in the trans to wear and that's why it finally blew apart. I'm still confused as to why the trans and rear pinion angles are so off. As PJ stated, the engine and trans angle is very close to factory at 4.1*, but the rear is at 0.5*. The components, while not original to the car are correct to the architecture. Unless the rear ends had different mounting locations for 64-67 and 68-72. Does anyone know if that is true?


Regardless, like I said, when going through the process of elimination, you can guess or you can prove, but proving will expedite your cure. 

If I had another set of wheels or a buddy with them, or a known good spare, or access to a balancer, I would at least attempt to eliminate the wheels from the equation. It's going to be easier than swapping out your upper arms and then adjusting them. And also easier than swapping out the trans mount, which again would be a guess.

I spent 6 months of Hell (and $2000) chasing a stalling issue. I turned out to be a free, 15-minute valve adjustment. 

Of all the things that might be causing vibration, the wheels are the single thing that you can check off your list.


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## armyadarkness (Dec 7, 2020)

So you swapped the entire diff housing?


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## NoGoat (Jul 21, 2021)

armyadarkness said:


> Regardless, like I said, when going through the process of elimination, you can guess or you can prove, but proving will expedite your cure.
> 
> If I had another set of wheels or a buddy with them, or a known good spare, or access to a balancer, I would at least attempt to eliminate the wheels from the equation. It's going to be easier than swapping out your upper arms and then adjusting them. And also easier than swapping out the trans mount, which again would be a guess.
> 
> ...


Fair enough, point taken.

Yes, swapped the entire diff housing.


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## michaelfind (Dec 14, 2018)

It's no wonder I can't recall the difference. I can find all sorts of conflicting information regarding 64-67 vs 68-72 rear upper control arms. One is shorter than the other, but who knows which. The consensus does seem to be to use the control arms designed for your car NOT for the rear end you are installing. I keep waiting for Bear or PJ to chime in with the facts and stop my rambling. But at least I cleared up the wrong guidance I gave you earlier.


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## NoGoat (Jul 21, 2021)

michaelfind said:


> It's no wonder I can't recall the difference. I can find all sorts of conflicting information regarding 64-67 vs 68-72 rear upper control arms. One is shorter than the other, but who knows which. The consensus does seem to be to use the control arms designed for your car NOT for the rear end you are installing. I keep waiting for Bear or PJ to chime in with the facts and stop my rambling. But at least I cleared up the wrong guidance I gave you earlier.


For what it's worth...the *64-67 upper arms are longer at 12-3/4"* and the* 68-72 are 10-1/4"*.
I have the original upper arms with new bushings in my 67 and new boxed lowers for a 67. As far as I can tell the rear housing doesn't have any noticeable differences in where the arms mount based on year. There are a couple other differences like flat vs domed spring mounts.


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## armyadarkness (Dec 7, 2020)

WOW! Those length differences see/ sound drastic


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## armyadarkness (Dec 7, 2020)

If you swapped rear housings I would imagine that your problem lies in that area


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## michaelfind (Dec 14, 2018)

armyadarkness said:


> WOW! Those length differences see/ sound drastic


I guess if you got the wrong one, you could adjust all day and still never get the angles right.


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## NoGoat (Jul 21, 2021)

armyadarkness said:


> WOW! Those length differences see/ sound drastic


Yeah, for the new body architecture for 68 the upper body mount must have moved rearward that amount.

That said, I didn't think that the trailing arm mount locations on the rear housing varied that much over the years.


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## PontiacJim (Dec 29, 2012)

NoGoat said:


> For what it's worth...the *64-67 upper arms are longer at 12-3/4"* and the* 68-72 are 10-1/4"*.
> I have the original upper arms with new bushings in my 67 and new boxed lowers for a 67. As far as I can tell the rear housing doesn't have any noticeable differences in where the arms mount based on year. There are a couple other differences like flat vs domed spring mounts.


I find the same numbers - Center hole-to-Center hole. Rear lower arms are the same at near 22" C-2-C.

From Dick Miller's book on driveshaft/pinion angles:

When you measure your driveshaft angle down (ie 1.5 degrees down) and the pinion angle (ie 3.5 degrees down in the opposite direction), adding the two together gives you 5 degrees total negative pinion angle.

The book says to use the angle finder (I got mine at Home Depot and has a magnetic base) mounted on the rear/backside of the rear axle housing which is a good place to take measurements on GM rear axles as it is typically flat.

So if I am reading this correctly, you would first want to pull your angle off the driveshaft just behind the U-joint at the transmission output yoke (driveshaft installed), then take your pinion angle off the back of the rear axle (if you have a straight/flat spot). Then add these 2 together and see what you come up with and adjust from there.

PJ- Adjusting the upper control arms using aftermarket adjustable arms - extending them will rotate the pinion angle up (postive) and shortening them will rotate the pinion angle down (negative).


Start with 2 degrees negative pinion angle for cars in the 400HP range, 4 degrees for cars in the 600HP range.

Once you make an adjustment, go back and take the driveshaft/pinion angle again and see where you are. Keep adjusting until you get your numbers.

Other things to check:

Sometimes rotating/flipping the driveshaft 180 degrees in the pinion yoke can help. I know on Chryslers they have a specific way they are set up and if you don't mark the driveshaft/trans input shaft/rear pinion and then go install new U-joints and just slap the driveshaft in any which way, you can wind up with a vibration.

Check the U-joints for slop/play even if new. Have had it where 1 needle bearing dropped out of the cap while installing the U-joint into the driveshaft - but caught it.

Make sure your "C-clips" are actually locked into their grooves on the cap and fully seated. Another near miss as I had no problem getting the C-clip over the U-joint, problem was the cap was not perfectly seated just enough so the C-clip did not fall into the cap's groove, but looked pretty good until I compared it to the opposite side and could see the C-clip appeared "thicker" because it had not set down into the groove.

Even with all this, you cannot discount a bad wheel bearing, front or rear, and as pointed out bent rim OR a belt broken/slipped if radial tires. If you see a "pucker" mark on the tire's side wall, that's a good sign of a tire issue, not the driveshaft.

You could also take the driveshaft to a service that can check the balance. It could be bent, dented, or lost a weight.


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## NoGoat (Jul 21, 2021)

PontiacJim said:


> I find the same numbers - Center hole-to-Center hole. Rear lower arms are the same at near 22" C-2-C.
> 
> From Dick Miller's book on driveshaft/pinion angles:
> 
> ...


As always, great points. I have a lot of things to check.

On a positive note, I just went and cruised a very busy and slow Woodward Ave, and engine temperature never got above 190*. That would have never been possible for the last 25 years. So with this forums help I’m confident I can get this fixed too.


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## CoveKid19 (Nov 18, 2021)

NoGoat said:


> As always, great points. I have a lot of things to check.


*Any update on your vibration issue?*

I'm in the process of installing a new trans (TKX) and noted all the angles before taking things apart.
The angles in my 66 were nearly identical to yours and I had no detectable vibration whatsoever.
Transmission = 4.1° down in rear
Driveshaft = 1.2° down in rear
Differential = .3° up in front

Though I didn't have any vibration, I did notice the rear u-joint has needle wear marks with less than 1k miles.. From what I've read, this is caused by the angles being close to the same and not allowing the joint to rotate sufficiently. That made sense when I checked how far the diff will raise in the front with a jack. Forcing the front of the diff up, it moves approx 1° before the wheels just start to lift which tells me the angle would be around 1.3° when cruising under a light load. Going down to have the driveshaft shortened next week so I'll see what the shop has to say.


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## NoGoat (Jul 21, 2021)

CoveKid19 said:


> *Any update on your vibration issue?*
> 
> I'm in the process of installing a new trans (TKX) and noted all the angles before taking things apart.
> The angles in my 66 were nearly identical to yours and I had no detectable vibration whatsoever.
> ...





CoveKid19 said:


> *Any update on your vibration issue?*
> 
> I'm in the process of installing a new trans (TKX) and noted all the angles before taking things apart.
> The angles in my 66 were nearly identical to yours and I had no detectable vibration whatsoever.
> ...


So it’s hard to say. The adjustable upper arms were a good investment, the ride seems to have improved a bit. After all my farting around, I’m pretty sure my vibration is in the transmission pump. I’m going to swap in a 200 4r this year, so I’ll report back then. Good luck with yours.


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## CoveKid19 (Nov 18, 2021)

NoGoat said:


> So it’s hard to say. The adjustable upper arms were a good investment, the ride seems to have improved a bit. After all my farting around, I’m pretty sure my vibration is in the transmission pump. I’m going to swap in a 200 4r this year, so I’ll report back then. Good luck with yours.


Thanks NoGoat. I picked up a set of adjustable uppers that I plan on installing later today.


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