# New Rear



## GTO JUDGE (May 14, 2005)

Happy happy JOY JOY ..... NEW rear end ready to go in. 3:55 posi. Out with the 4:10's.


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## 05GTO (Oct 6, 2004)

GTO JUDGE said:


> Happy happy JOY JOY ..... NEW rear end ready to go in. 3:55 posi. Out with the 4:10's.


arty:


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## 68greengoat (Sep 15, 2005)

Nice rearend....:lol:


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## jetstang (Nov 5, 2008)

That will really help it on the highway, bring the Rs down some. Nice looking rear ya got there..


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## GTO JUDGE (May 14, 2005)

My speedo now is off by 12-13mph at 60-65mph. That's with a 43 tooth gear I installed a year ago. (was 18mph off with the OEM one) Tachs at 3K at about 65mph. Ordered a 45 tooth speedo gear. Calculations say I should be off about 2.5-5mph or so at 60mph. Hopefully taching at 2700 or so at 65mph. OEM wheels were 14x6 I have 14x7 on it which adds to the % off. This will be close enough I can handle a 5% difference the 30% was putting a lot of undriven miles on the odometer. Everything should be smoother with the new rear.


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## geeteeohguy (Feb 2, 2008)

Judge, great move. You'll be able to go FASTER, go FURTHER, for less MONEY! I never understood why people think a big ol' Pontiac engine needs a low gear to make it go! 3.55 is an excellent gear for head-snapping around town, and you can actually go down the hiway with it too.


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## 68GTO4004Spd (Jun 19, 2008)

GTOJUDGE how do you calculate the speedo gear that you will need? Can you post the math?


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## GTO JUDGE (May 14, 2005)

68GTO4004Spd said:


> GTOJUDGE how do you calculate the speedo gear that you will need? Can you post the math?


Here is a link I have that shows the gears and a formula. Speedometer Gear, Speedometer Gears, Ford, GM, Dodge 700R4

Part way down you'll see : Speedometer Calculator click here with a odometer going fast... this will open up to a calculator that will do the calculations for you.

I had a guy there help me out when I called. I will see exactly how far off I am with the driven gear and if its minimal I will live with it. If I want it exact I will have to go a step further and install a drive gear.


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## GTO JUDGE (May 14, 2005)

geeteeohguy said:


> Judge, great move. You'll be able to go FASTER, go FURTHER, for less MONEY! I never understood why people think a big ol' Pontiac engine needs a low gear to make it go! 3.55 is an excellent gear for head-snapping around town, and you can actually go down the hiway with it too.


I think this car was abused and raced at one time. Someone spent money to get it away from it was, I'm spending money to get it back. New Trans, New rearend, strong motor..... I'm gettin there....


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## jetstang (Nov 5, 2008)

GTO JUDGE said:


> I think this car was abused and raced at one time. Someone spent money to get it away from it was, I'm spending money to get it back. New Trans, New rearend, strong motor..... I'm gettin there....


After you got the engine done and said that it felt really strong, I didn't know you had 4.11s in it, I bet it was damn quick. 4.11s are fun, but suck on the highway, even at 55 MPH. I had 4.88s once with a Big block, it was 3200 RPMs at 45 MPH in fourth, but man that thing was stupid fast!


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## GTO JUDGE (May 14, 2005)

jetstang said:


> After you got the engine done and said that it felt really strong, I didn't know you had 4.11s in it, I bet it was damn quick. 4.11s are fun, but suck on the highway, even at 55 MPH. I had 4.88s once with a Big block, it was 3200 RPMs at 45 MPH in fourth, but man that thing was stupid fast!


The Trans was rebuilt to TH400 specs the engine had work done... new timing chain, fuel pump, water pump, harmonic balancer, front seals, rear main seal and a tune. The issue when the valve covers were off were some missing valve spring "hats" and some cracked ones. The guy working on the engine said he was afraid parts of the "hat" may have fallen into the engine when he was yanking around the crank shaft. At that point I decided to go with an engine rebuild, to be safe but all is well. The car was driven like this for 15 years before I got it and a year that I had it. No problems. I learned those "hats" are not necessary and the racing outfit I talked to about a rebuild told me they don't even install them, they are not necessary.....so.. with the engine working fine, no smoking, no oil burning, no leaking, lots of pep I decided to leave well enough alone and get the rear end addressed.

I would like to drive highway without the high whining and extra umpf of the engine. I had a guy in Ohio build this rear end, it's new so I am looking forward to getting it in. Then pulling the motor to clean and paint and restore the engine bay. 

I wanted to keep the 12 bolt but I also wanted the rear to be what is called for, so I almost broke even on a swap when I sold the 12 bolt. I don't need the 12 bolt so the 10 is fine.

The car does have a lot of kick to it and when shifting through the gears it goes but keeping in mind the engine is old I am cautious on how much I get on it. With the 4:10's it shifted quick into 2nd gear and with the 3:55's it will not shift as quick I am told. The guy that rebuilt the tranny can adjust the governor to my liking if need be, I will see.....


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## GTO JUDGE (May 14, 2005)

The operation was a success. I can actually go 60-65mph at 2800 rpms instead of the 3000+. Got to 70mph and it was taching 3100. 
Added the 45 tooth driven gear and that combined with the 3.55's took me from 13mph over at 60 to 2mph. Speedo is spot on until 55 mph then it goes to 1mph over. I have wider tires on it which is causing the out of calibration reading.... 14X7"x60's. Very happy with the change, and results it's a bit quieter too. 
Nov 28th the motor gets pulled some new parts added, some cleaned up, parts of motor dissembled for painting, freshening up the engine bay. She lookin' fine.


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## Indecision (Oct 24, 2010)

Taching high on the highway is my biggest gripe about the 4spd, but I love the 4.10s. I wish a T56 would just bolt up.

Congratulations on your success. I have thought about swapping to 3.73s several times.

And Jetstang, was the car with 4.88s a 1/8th mile car? Just curious.


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## GTO JUDGE (May 14, 2005)

Indecision said:


> Taching high on the highway is my biggest gripe about the 4spd, but I love the 4.10s. I wish a T56 would just bolt up.
> 
> Congratulations on your success. I have thought about swapping to 3.73s several times.
> 
> And Jetstang, was the car with 4.88s a 1/8th mile car? Just curious.


My buddies '69 Judge, we drove each others for comparisons... He's taching 3200 at 60mph. Off by 5mpg at 60mph too. His is a 4 speed I think he has 3.73's maybe 3.90's in it.


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## Eric Animal (Oct 28, 2007)

I put a 3.73 rear in my car. Also using a 4L80e trans with .75 to 1 OD....the OD will give a final drive of a 2.79 rear.


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## ppurfield001 (Jan 21, 2008)

Eric Animal said:


> I put a 3.73 rear in my car. Also using a 4L80e trans with .75 to 1 OD....the OD will give a final drive of a 2.79 rear.



I have a 3.55 to one rear with a Keistler five-speed that lets me run at 1,900 RPM over 60 MPH in fifth gear. Good luck, your car is really coming along Judge.


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## Indecision (Oct 24, 2010)

The 4.10s don't scare me, I just wish I could fit a T56 without cutting out the transmission tunnel, I can't justify a Lenco for the price (assuming it would fit) and I would have to cut up the floor to fit 6 shift levers, and there isn't a good bolt up 6spd solution for these cars. It blows.


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## 66tempestGT (Nov 28, 2009)

you can make any amount of shifts with a lenco from 2 on up depending on how many segments you stack together. although i can't think of any reason you would want to. a six speed lenco would be about 5 feet long including the bellhousing. and a ridiculous waste of money. :willy:


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## jetstang (Nov 5, 2008)

Indecision said:


> And Jetstang, was the car with 4.88s a 1/8th mile car? Just curious.


I figure it was, I never took it to the strip, 25 miles away, and it revved too high. And my L60s wouldn't of hooked anyway, but it was FUN!! That was in 92. Had dual carbs on it, got 3 MPG!! Swapped to a single 4 and got 9 MPG.


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## GTO JUDGE (May 14, 2005)

Indecision said:


> The 4.10s don't scare me, I just wish I could fit a T56 without cutting out the transmission tunnel, I can't justify a Lenco for the price (assuming it would fit) and I would have to cut up the floor to fit 6 shift levers, and there isn't a good bolt up 6spd solution for these cars. It blows.


Someone spent $$ transforming it to race, all the evidence pointed to it. While it suited that guy, the car is now retired from racing, I am now spending some serious $$ to get it back and to do it right. I don't do a lot of highway driving with it because of the high rev's, I debated removing that rear, but I want the car restored to where it should be, or pretty close to it. When I drove it on the TP that motor was laboring pretty good at only 55mph. From traffic light to traffic light that thing would knock the snot out of anyone, and the gas gauge was constantly moving backwards  I really don't need those gears for what I want it for, just to cruise and show. The guy I sold it to is putting it in a '71 and modifying the car with overdrive so this ideal for him.

At the ripe old age of 53 I am getting into the craze that I missed out on in my 20's. Thing is now, the memory ain't what it was


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## Indecision (Oct 24, 2010)

66tempestGT said:


> you can make any amount of shifts with a lenco from 2 on up depending on how many segments you stack together. although i can't think of any reason you would want to. a six speed lenco would be about 5 feet long including the bellhousing. and a ridiculous waste of money. :willy:


I know this, hence why I said that I can't justify it for the price (a 6spd would be about 7 grand), and assuming it would fit. I knew it would be long, but it is shorter in height than the T56. Like I said, I just wish there was a good bolt up 6spd solution for these cars.


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