# Need Help with my 1971 GTO that has a 1970 Axle and putting new gears in the rear end



## Bobs1971 (Nov 12, 2021)

NEED YOUR HELP ON AN ISSUE

I have a question for you. I went to a shop in town to change my gears (rear axle) out from the freeway flyer gears I have to something that will help me leave the line a little quicker. The shop ordered new gears and bearings for my 1971 GTO and then waited a little to install because of work in front of my car. Well when they pulled my rear axle apart they learned that I had a 1970 axle not a 1971 and the parts they ordered (gears and bearing) do NOT fit and bolt into place. The shop bought 3.44 gears and I had 2.56 gears in my factory rear axle. I am being told they cannot find gears for my 1970 axle so the shop is trying to source a 1971 housing for the differential so the parts acquired will bolt into place.

Long story short is they are having a hard time finding the parts and have had my vehicle for a year now. I am to the point where I just want to have my car put back together the way it was. Can I find gears for a 1970 GTO axle ? or how would one find a housing for a 1971 differential that will work with a 1970 axle.

I have a 400 cubic inch engine with a 4 barrel-its an automatic

I’m not super mechanically inclined just want my car back and running the way I hoped it would be by now.

Thanks for any help you can offer.


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## PontiacJim (Dec 29, 2012)

Bobs1971 said:


> NEED YOUR HELP ON AN ISSUE
> 
> I have a question for you. I went to a shop in town to change my gears (rear axle) out from the freeway flyer gears I have to something that will help me leave the line a little quicker. The shop ordered new gears and bearings for my 1971 GTO and then waited a little to install because of work in front of my car. Well when they pulled my rear axle apart they learned that I had a 1970 axle not a 1971 and the parts they ordered (gears and bearing) do NOT fit and bolt into place. The shop bought 3.44 gears and I had 2.56 gears in my factory rear axle. I am being told they cannot find gears for my 1970 axle so the shop is trying to source a 1971 housing for the differential so the parts acquired will bolt into place.
> 
> ...


You are not really giving us enough info to answer your question.

Assume the rear-end is a 10-bolt rear end. A Pontiac 10-bolt is a Pontiac 10-bolt. It is called and 8.2 because the ring gear is 8.2" in diameter. They are the same up to 1972.

However, there is a later 10-bolt that came out in 1971 that was used by Olds & Buick and later by all GM cars - it is an 8.5 10-bolt because the ring gear is 8.5" in diameter. The 8.5 10-bolt became the "corporate" rear end for GM so it can be found under most GM cars basically from 1972 and up.

First question - Obviously your 10-bolt rear end has been changed? You have a 1971 car and the garage is saying you have a 1970. Did the shop have to unbolt the 4-bolts that hold the retaining plate that holds the axle into the center section (called the carrier)? If they had to unbolt the 4 bolts and pull the axle, it is a Pontiac rear end. IF they had to remove the "C-Clip" at the carrier in order to pull the axle out, then it is a Chevrolet 10-bolt rear end, and not a Pontiac rear end. Chevy is different than a Pontiac. So we need to know how the axle had to be removed - 4-bolts & metal retainer, or C-clips.

The axle is stamped with an axle code that will identify it, as well as a casting number, and a casting date. All these can be used to identify what rear end you have - Pontiac/Chevy, axle ratio, year the rear end was made. If they work on rear ends for a living and do gear changes, they should be very versed in knowing this kind of thing.

Axles have splines that get inserted into the carrier. They can be 28, 31, or 35 splines depending on the rear being a standard/regular production rear end (28 splines), high performance (31 splines) and aftermarket for racing (35 splines). But I believe you are using the term "axle" to mean rear end, correct?

The Pontiac 10 bolt 8.2 only changed the ring gear bolt from 3/8 24 thread right hand bolts 1964- early 68 and went to 7/16 20 thread count left hand thread from late 1968 to 1972 and beyond. You have to watch the Pontiac gears as the 7/16" 20 thread posi carriers can only be used with 7/16" gear set...all after market Pontiac 8.2 gears use 3/8" 24 right hand thread. Most gear sets uses 3/8" bolts. Some factory gears use 7/16" bolts. If the factory case uses 7/16" bolts you will need to purchase YSPBLT-027 spacers.

The 8.2-inch 10-bolt axles were originally equipped with one of three carriers: one for 2.76:1 and lower gearsets; one for 2.94 to 3.23:1; and one for 3.36:1 and higher ratios.

With what you are saying, I believe what your shop is telling you is that the 2.56 carrier used to bolt the ring gear onto will not work with the 3.44 (believe you mean 3.55?) gears they bought.

See the above. You need a specific carrier for the range of gear sets when swapping gears. 3.55 gears will not work with the 2.56 carrier - and they should have known this IF they know what they are doing. You need a 3.36 and up rear gear carrier if stock.

You may be able to purchase a posi carrier that will either work with the gears your shop has or buy a complete kit. If you go the kit route, contact them to make sure the gears will work with the carrier. They list the 3.55 gear as an option, so assume the posi unit will work with these, and other, gear ratios. Click on the link below.

GM 8.2" BOP Yukon Duragrip Posi LSD Elite Gear Pkg 


The shop is the one who ordered the gears/bearings - so you owe them nothing, they have to eat those parts. I would not allow them to "source" another rear end because they may run into the same thing - 3.55 gears won't work if you don't have a 3.36 and up rear gear. If they cannot get gears/bearings to work with the rear end that is under the car, pull the car out and bring it to someone who does know what they are doing. I would also not pay them a dime - they own the wrong parts they ordered and supplied. They should also reassemble the rear end back together so you can drive it out of there - again, no charge to you because they took in a job they were not qualified to do and you should not be paying for the work that they could not complete.

I apologize if I am reading this wrong, but it sounds like you have a couple clowns with metric adjustable wrenches and no knowledge on what they are doing and you are the one who is not enjoying your car.


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## Bobs1971 (Nov 12, 2021)

I will get some answers to some of this. Like I said I am not the most mechanical guy when it comes to this stuff and I really appreciate your knowledge. This whole gear change has been a complete cluster, super frustrating. Thanks for the info.


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## 1969GPSJ (Feb 26, 2020)

Bob,
Welcome to the site, I have found everyone here is very helpful
Maybe the gear set is a 3:42??
Maybe this site will help with some" differential ID", the guy who builds these rears super nice 



Home


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## armyadarkness (Dec 7, 2020)

Gears are intimidating, but Ive swapped them, on my back in a driveway, many times. It doesn't take long, but it does require tools which you can rent... or if you bring the parts to a NAPA, they may press bearing on for you.

My point being, get your car out of there and tackle this another way. From what you posted, the shop doesnt seem motivated.

Also, make sure you have your; location in your profile because you may live close to another member, who can help.


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## Bobs1971 (Nov 12, 2021)

armyadarkness said:


> Gears are intimidating, but Ive swapped them, on my back in a driveway, many times. It doesn't take long, but it does require tools which you can rent... or if you bring the parts to a NAPA, they may press bearing on for you.
> 
> My point being, get your car out of there and tackle this another way. From what you posted, the shop doesnt seem motivated.
> 
> Also, make sure you have your; location in your profile because you may live close to another member, who can help.



Updated my profile thanks. Added a pic of the car


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## Bobs1971 (Nov 12, 2021)

1969GPSJ said:


> Bob,
> Welcome to the site, I have found everyone here is very helpful
> Maybe the gear set is a 3:42??
> Maybe this site will help with some" differential ID", the guy who builds these rears super nice
> ...


I put a request to join their forum and I need to get some additional info about my situation from the info Pontiac Jim sent me. Wish I was a little smarted when it came to this stuff. I took my car to a shop that was well referred to me but it hasn't worked out like I was hoping.


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## armyadarkness (Dec 7, 2020)

Im in Jersey, so trading me a six pack to do your gears will only work if you have some serious gas money


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## PontiacJim (Dec 29, 2012)

Bobs1971 said:


> I put a request to join their forum and I need to get some additional info about my situation from the info Pontiac Jim sent me. Wish I was a little smarted when it came to this stuff. I took my car to a shop that was well referred to me but it hasn't worked out like I was hoping.


We all hate when what you are experiencing happens - we have heard this story from others right down to having the car parted out because the person was recommended and trusted. You trust the shop and then it turns into a cluster. There are those who somehow gain a good reputation working on older cars, but there are certain things on a car I feel a specialist is needed. I can remove/install and automatic transmission, but I would not rebuild one. I might be able to do so, but then again, I don't do enough to be able to spot right away a problem or worn part. Then I would re-assemble it and have nothing but problems - wasted money/time. Same goes with a rear end. I can purchase all the needed parts knowing what I have, then let a shop that specializes in rear end work whip it together because they have the car lift, tools, and knowledge.

You just have to know when to NOT listen to someone who recommends a shop that is not a specialist and does more general work. You also don't want a shop that is great on the newer/modern cars and can tune them up and rebuild any given part on them. Our older cars are different and it takes experience working on them and knowing the ins & outs because a great shop that works on some of these modern rockets can't apply the same knowledge or techniques to the older cars, and vice-versa.

Personally, if I didn't get a call in 1 month after dropping it off, I would be down there getting answers and a solid date as to when the car will be done - not excuses or generalities and guesstimates on how much it is going to cost you. A good shop can give you a price they will hold to and a timeframe for the job to be completed. Otherwise, those are the shop you run from.


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## 1969GPSJ (Feb 26, 2020)

Bob 
I would not hesitate to have the shop reassemble the rear if needed and have the car taken back home , towed if needed!
That way you can control everything moving forward, I have heard nightmares where the shop starts charging storage an people lose their property 
We have all paid our tuition at one point or another, I have had to swallow my pride in the past but I walked away with a valuable lesson and my property.


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## LATECH (Jul 18, 2018)

you cant bolt a 3 series gear onto a carrier for a 2 series gear anyhow. So get a new posi carrier for a 3 series gearset
If you do happen to have that odball olds rear , dump it for a good ol 8.2


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## LATECH (Jul 18, 2018)

69gpsj has a great point.
Besides , probably best to get a bone fide 8.2 ,, in case you have the funky olds rear. Build that rear and swap them out. That way it should be a weekend swap


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## Bobs1971 (Nov 12, 2021)

Hey guys I did get some additional info. For some reason my 71 GTO has a Buick rear axle thats a 71 (with freeway flyer gears) 2.5 or something close and I have been told you cant get parts for the axle (someone said its a turd). Was mentioned that I could get a 70-72 Pontiac axle and reuse the housing or get a 67-72 whole axle from a Pontiac or Oldsmobile but if its an Oldsmobile make sure it has a 10 bolt cover. I dont know if I want some rusted up thing sitting out on a junkyard but thats the route I will go first. The guys at the shop has the gears to rebuild whatever he finds. Your thoughts.

I have stopped into the shop 3 times in the last week and now he is moving on it. I do think I may pull it and take it to a specialist though or talk to the specialist and see what he says


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## O52 (Jan 27, 2019)

If your going through all that trouble and don't mind originality, get a Chevy 12 bolt or Ford 9". Both have large aftermarket support.


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## PontiacJim (Dec 29, 2012)

Bobs1971 said:


> Hey guys I did get some additional info. For some reason my 71 GTO has a Buick rear axle thats a 71 (with freeway flyer gears) 2.5 or something close and I have been told you cant get parts for the axle (someone said its a turd). Was mentioned that I could get a 70-72 Pontiac axle and reuse the housing or get a 67-72 whole axle from a Pontiac or Oldsmobile but if its an Oldsmobile make sure it has a 10 bolt cover. I dont know if I want some rusted up thing sitting out on a junkyard but thats the route I will go first. The guys at the shop has the gears to rebuild whatever he finds. Your thoughts.
> 
> I have stopped into the shop 3 times in the last week and now he is moving on it. I do think I may pull it and take it to a specialist though or talk to the specialist and see what he says


PERFECT! The 1971 Buick is the much stronger, like 12-bolt stronger, 8.5" rear axle. Do not swap it out, use it to build off of.

What is the axle spline count? That is what you need to know. Appears they are 28 spline.

Ebay has a set- cheap enough for the pair.

Moser can make you any axle you want, but it will not be inexpensive.

Yukon Gear & Axle has a new ring & pinion - 3.42 ratio, 28 spline application for the Buick.

Yukon offers a posi section for the 28 splines for the above gears.

You can't put 8.2 guts into an 8.5 housing.

So, if me, pull the car and bring it to a shop that knows what they are doing. Verify that you have the 28 spline axles and if you need one, go the Ebay route .

Email/call Yukon and let them know what you have and what you will need to do the installation. They have the gears, posi, and should have a complete installation kit. See what they have in stock and make sure it will work with your rear end set-up.

I believe you can use any GM 8.5 carrier as the GM 8.5 was a corporate rear end used in many cars and GM makes for a number of years.

You can try to locate a used rear end assembly and hope you get something good you can use, but since a lot of this stuff is 50 years old, you may be throwing your money away on junk. You know what you have under your car. It fits. No hassles with brakes and lines if you get something you have to work with. You know the rear end is good and works.

Just my opinion on all this as I am no rear end/axle specialist. I went with a new Ford 9" with my build as the 10-bolt was worn out and would not hold up to the higher HP/TQ of my engine. Not inexpensive, but I know it is all new and I won't ever have to mess with it in my lifetime. Some go with a new 12-bolt. So it is your call.


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## Bobs1971 (Nov 12, 2021)

Thanks for the info


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