[jhein]

So my car is in the shop having some things done, including the gear change. My guy calls me today and says it has 4.88 gears in it. He counted the teeth 3 times to be sure. That was a surprise. I thought it was probably a 4.11. Based on that I won't do the 3.08. Probably 3.31 vs 3.55. Now I need a new carrier too.

[R 70 Judge]

My 70 Judge had a M20 and 3.55 gear and I thought it was a good compromise between acceleration and freeway cruising

[Formulabruce]

Not sure a 3.31 is available anymore. 3.42 is pretty popular.
Make SURE they Shim the front pinion seal OUT away from the carrier by 1/8" . Use a rod, or thick wire or make a giant 1/8 "washer. If they don't, it will leak. The seals now available are Not for this type of shorter nose housing.
If installed flush, the seal will not ride on the yoke shaft flat part, but rather on its front edge which has a chamfered edge.
(12 bolt only, includes GTO, Z-28, ETC)

[jhein]

Originally Posted by Formulabruce

Not sure a 3.31 is available anymore. 3.42 is pretty popular.
Make SURE they Shim the front pinion seal OUT away from the carrier by 1/8" . Use a rod, or thick wire or make a giant 1/8 "washer. If they don't, it will leak. The seals now available are Not for this type of shorter nose housing.
If installed flush, the seal will not ride on the yoke shaft flat part, but rather on its front edge which has a chamfered edge.
(12 bolt only, includes GTO, Z-28, ETC)

Thanks. I'll be sure to mention that. The guy working on the car is a custom car builder but he's sending the rear end out to a specialty shop for the rebuild.

[Aus78Formula]

Sounds like the perfect gear ratio for tree climbing

[unruhjonny]

Originally Posted by jhein

So my car is in the shop having some things done, including the gear change. My guy calls me today and says it has 4.88 gears in it. He counted the teeth 3 times to be sure. That was a surprise. I thought it was probably a 4.11. Based on that I won't do the 3.08. Probably 3.31 vs 3.55. Now I need a new carrier too.

ok - I TOTALLY understand now why you thought the gearing was too high!!

you will probably be quite happy with the standard gearing that '70 Trans Am's received 3.55:1.

[Norwood]

Originally Posted by jhein

Thanks. I'll be sure to mention that. The guy working on the car is a custom car builder but he's sending the rear end out to a specialty shop for the rebuild.

JMHO. I’m very happy with my factory 355. I’d be careful telling the guy setting up my rear end how to do his job. I know what I would tell someone telling me how to do mine.

[Formulabruce]

Originally Posted by Norwood

JMHO. I’m very happy with my factory 355. I’d be careful telling the guy setting up my rear end how to do his job. I know what I would tell someone telling me how to do mine.

That said;, And respected, Better to only have to do it once. Learn from my mistakes.
Maybe print it out and put with the rear end so the builder can say "I caught this potential problem for ya"
Have seen MANY "mechanics" Disregard advice about water pump divider plates, and work had to be re done.....
The good ones are always willing to LEARN, or look at options.

[jhein]

Actually, the guy that's doing the work for me seems very good and so far, I trust him. If I didn't. I wouldn't let him touch the car. He's been doing this for a long time here and he has a shop that he uses for rear ends. If he/they screw it up he'll either stand behind his work or never see me again. But so far I have a good feeling about it.