GM 8.5 10 bolt

[68400BIRD]

I am looking at a 10 bolt rear end on craigslist and I was told that it came out of a 1968 camaro. I need one for a 1968 firebird. I know they will swap right over for all three years. The only two main differences being the pontiac had 8.2 and 67 had mono leaf. He told me this rear end was out of his 68 but is for mono leaf. Did they put mono's in 68 camaros. I know they stopped in 67 on firebirds.

[big gear head]

All first gen Camaro 10 bolt rear ends had mono leaf springs. The first gen Camaro 10 bolt was the 8.2. The 8.5 wasn't used until '71 and the Nova 8.5 rear end that fits the first gen Camaro wasn't used until '72. If this is a '68 rear end then it will be the 8.2 10 bolt, not the 8.5.

[68400BIRD]

Will the 8.2 hold up to 400hp with street tires? Or should I scrap the idea and put in the 12 bolt that I talked to you about a few weeks ago?

[68Formula]

If it's an 8.5 out of a Nova, then it's a good piece. The 8.2 is weak and probably not worth the risk to try as is, or put in the money to beef it up. The stock 8.2 4 pinion Firebird rears are a little stonger than the Chevy and don't use a C-clip, but you might be limited in what gears you can purchase.

[68400BIRD]

OK I called the owner back and he says that it is a 8.5 rear end. He thinks it might be out of a nova. He said that it has the two square corners on the bottom of the diff. Are there any other ways of making sure that it is not a 8.2 before I buy it?

[69LT1Nova]

Don't bother with the 8.2" rear. As was said previously, find an 8.5" from a '72 and up Nova.

[69LT1Nova]

OK I called the owner back and he says that it is a 8.5 rear end. He thinks it might be out of a nova. He said that it has the two square corners on the bottom of the diff. Are there any other ways of making sure that it is not a 8.2 before I buy it?


Yeah, get the axle code off the rear and cross check it using this website: http://www.novaresource.org/axle.htm

[68400BIRD]

Thanks, I printed that off and will take it along with me. My main concern now is that he's claiming that it has 3:73's and that was not a gear option for any of the 10 bolts from the factory. They could have been put in at a later date but I hope it's not a typo and he meant 2:73's which were a common gear back then.

[68Formula]

Should be easy enough to tell. Rotate the wheel and count the revolutions of the coupling.

If it's a posi, one rotation of the wheel = 3.73 rotations of the coupling. For non-posi, you'll need to rotate the wheel two times .

To know whether it's a posi, for the posi, both wheels go in the same directoin. Non-posi or worn out, one side would either stay put or more likely rotate in the opposite direction of the other wheel.

3.73 gears are a very common swap for 8.5s. Nice thing about them is there is a huge range of ratios available without having to change the housing series or use shim adapters.

[68400BIRD]

Thanks for all the info. I will check on the rear end tonight. I hope everything pans out because it's a decent price and a lot cheaper than what I have to do to the 12 bolt.

[big gear head]

If it's an 8.5 with mono leaf perches then it's kind of rare. Most of the 8.5 rear ends had multi leaf perches. I was talking to someone a few days ago that was looking for a mono leaf 8.5 rear end. I told him good luck finding one.

[68400BIRD]

Well good news and bad news. The seller had no idea what he had. It was not a posi or limited slip unit and it was not 3:73 gears. The some what good news is that he just gave it to me when I told him I was not interested. The code off of the tube is JB G013 2 Can anyone decode this for me. From the one site that I was using it seems to be a 72-73 open 2:73 or 3:08 rear end.

[69LT1Nova]

Well good news and bad news. The seller had no idea what he had. It was not a posi or limited slip unit and it was not 3:73 gears. The some what good news is that he just gave it to me when I told him I was not interested. The code off of the tube is JB G013 2 Can anyone decode this for me. From the one site that I was using it seems to be a 72-73 open 2:73 or 3:08 rear end.

Congratulations! You are correct, it is a '72 and up 8.5". The only accurate way to determine the gear ratio is to take off the cover and count the teeth. You can count the revolutions of the wheels when you turn it over (as described previously)... but I find it easier to just count the teeth on the ring and pinion.

FYI - new gears and a posi are relatively cheap for that rear. The 8.5" has been known to handle 600 HP with an automatic trans when built right.

My 8.5" started life as a 2.73 open rear. Now it is a 3.42 posi with a full Richmond rebuild from Randy's R&P. Total cost including parts: $500.

[68400BIRD]

Wow! That was a great deal. I have been quoted a little over a $1.000 for a rebuild on either my 12 bolt or my old 10 bolt. I pulled the cover off at the sellers house but he did not have a floor pan to catch the gear lube. I need to look at the ring gear to check out the ratio.

[69LT1Nova]

The trick to most rearend shops is that they charge through the nose for parts. Find out if they will install the parts if you bring them to the shop. Randy's was way cool. I brought them a posi carrier and the Richmond rebuild/R&P... labor was only $200.