# 70 GTO differential



## zrone90 (8 mo ago)

I recently purchased a 70 GTO. The differential was very noisy and I took it to my mechanic. 
After inspection it was apparent that the ring gear was shot. It appears to be an 8.2 with bolted in axel's. It has posi and the bolts holding the ring gear are 7/16 left handed thread. My mechanic contacted his supplier and he sent him a 3.55 ring and pinion, Upon inspection the bolts were smaller and right handed thread. After contacting supplier he said to put sleeves on the bolts so they fit in the carrier without slop. he said he could not find an application that uses 7/16 bolts. 
To me this is making the ring and pinion weaker, anyone out there no where I could source the correct ring and pinion. Thanks


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## Scott06 (May 6, 2020)

He gave you gears fir the wrong 8.2” rear end. GM made a 8.2” 10 bolt rear that is different than the BOP 8.2” your GTO originally had…

these are for the chevy/gm 8.2 and are 7/16” left hand… GM 7.5, 8.25, & 8.5 Ring Gear Bolts

the BOP 8.2 uses 3/8” right hand thread bolts









GM 8.2 Ring Gear Bolts







www.ronsmachiningservice.net





so the diff in your gto has 7/16 bolts in It ? Or the replacement parts use a 7/16? If the diff has 7/16” the bop 8.2 rear was replaced with a GM 8.2 if thats the case… im assuming when u mentioned sleeves you have 3/8 bolts and a 7/16 hole in ring gear… if thats the case u were not given a BOP 8,2 ring and pinion…

this article shows how to id what you have , if your local supplier cant source i got good parts from rons machine when i did my gear swap.









10-Bolt Chevy Identification Guide. Know What You're Looking At


The Chevy 10-bolt rearend has really gained in popularity since the 12-bolt has become unobtainium. Find out how to ID that swap-meet find.




www.chevyhardcore.com


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## BLK69JUDGE (Jun 10, 2010)

I have a beautiful set of 336 gears ring n pinion with bearings factory gm late 67 date from a 30,000 mile 68 gto if needed


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## zrone90 (8 mo ago)

Sorry for the confusion. The old ring gear had 7/16 left handed bolts. The new ring gear has 3/8 right hand bolts. With the new ring gear they sent sleeves to go in the carrier to make up the difference off the smaller bolts. so I'm taking out a ring gear with 7/16 bolts and replacing it with a ring gear with 3/8 bolts. This makes me think the new ring gear with smaller bolts is weaker then the one I took out.
The suppliers can not find a ring gear application for the car that uses 7/16 bolts for the 8.2 diff. Are the not making these parts anymore or is the supplier wrong


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## armyadarkness (Dec 7, 2020)

If it were a Chevy 8.2, I think the axles would have c clips


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## zrone90 (8 mo ago)

armyadarkness said:


> If it were a Chevy 8.2, I think the axles would have c clips


No clips, bolted in axles


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## armyadarkness (Dec 7, 2020)

zrone90 said:


> No clips, bolted in axles


Yes, I know... my point is, if it were the Chevy rear, then I believe it would have c-clips. 

In other words, you likely have the BOP, and your mechanic got you gears for a Chevy.


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## armyadarkness (Dec 7, 2020)

However, I don't believe that BOP uses left hand threads, so either you have something confused, or someone really frankensteined something in there.

Based on what my comrades are saying, it should have bolt in axles and right hand threads (BOP).

Or

Clip axles and left hand threads (CHEVY).

Somehow you have a little of both?


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## Scott06 (May 6, 2020)

zrone90 said:


> Sorry for the confusion. The old ring gear had 7/16 left handed bolts. The new ring gear has 3/8 right hand bolts. With the new ring gear they sent sleeves to go in the carrier to make up the difference off the smaller bolts. so I'm taking out a ring gear with 7/16 bolts and replacing it with a ring gear with 3/8 bolts. This makes me think the new ring gear with smaller bolts is weaker then the one I took out.
> The suppliers can not find a ring gear application for the car that uses 7/16 bolts for the 8.2 diff. Are the not making these parts anymore or is the supplier wrong


Do you have a pic of the differential or cover from the rear? If it is scalloped on the sides of the cover it is a BOP 8.2 very distinctive cover. the sleeves fir the bolts take up the space between ring gear and smaller bolts? If thats the case then do original 7/16 bolts work with new ring gear?

this whole situation made me think back to when i swapped my 4.33s for 3.08s in 2020…i recall now having bolts i couldn’t use from the install kit. Looking in my install kit i found new 3/8 24 RH ring gear bolts left over… if you look in the attached pics there are two differentials , first one is the 4.33s that came out of my 65 GTO, second is the donor 3.08s that i got out if a 66 Gutlass in a u pullit yard years ago… the bolt heads are too big to be 3/8 bolts And these are both original GM
parts . If i get a chance ill dig up the 4.33 s out of the shed and take a bolt off.

what i would think is some 8.2s must have come with 7/16 bolts. Based on this i would assume your ring gear is 3/8” rh thread and they use the sleeve to make it fit the carrier with larger holes??


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## PontiacJim (Dec 29, 2012)

zrone90 said:


> No clips, bolted in axles



The 1970-72 Pontiac A-body 8.2 10 bolt rears used the tapered axle bearings with external seals. The axles for an A9 bearing are machined slightly different and have a smooth surface right outboard of the step in the axle so the external seal will have a smooth area to ride on. The ring and pinions had larger ring gear bolt holes and used a 1/16" larger LH threaded bolt to match.


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## zrone90 (8 mo ago)

Thanks for all replies and help. Finally got it figured out. Thanks again.


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## Bopman (7 mo ago)

zrone90 said:


> I recently purchased a 70 GTO. The differential was very noisy and I took it to my mechanic.
> After inspection it was apparent that the ring gear was shot. It appears to be an 8.2 with bolted in axel's. It has posi and the bolts holding the ring gear are 7/16 left handed thread. My mechanic contacted his supplier and he sent him a 3.55 ring and pinion, Upon inspection the bolts were smaller and right handed thread. After contacting supplier he said to put sleeves on the bolts so they fit in the carrier without slop. he said he could not find an application that uses 7/16 bolts.
> To me this is making the ring and pinion weaker, anyone out there no where I could source the correct ring and pinion. Thanks


Same thing happened to me in the 90's ....pretty sure the pinion will have issues too...at least mine did.


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## Bopman (7 mo ago)

armyadarkness said:


> However, I don't believe that BOP uses left hand threads, so either you have something confused, or someone really frankensteined something in there.
> 
> Based on what my comrades are saying, it should have bolt in axles and right hand threads (BOP).
> 
> ...





armyadarkness said:


> However, I don't believe that BOP uses left hand threads, so either you have something confused, or someone really frankensteined something in there.
> 
> Based on what my comrades are saying, it should have bolt in axles and right hand threads (BOP).
> 
> ...


Yes they were left hand threads my 3:55's in my gto were left hand threads.


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## armyadarkness (Dec 7, 2020)

zrone90 said:


> Thanks for all replies and help. Finally got it figured out. Thanks again.


You can't solve the crime and not tell us who done it!

Cripes bro... some of us are on the edge of our seats! You never know when your experience might save another one of us a ton of aggravation.


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