^HI, i want to put new gears in my 1971 Cutlass Supreme with 5,7 v8 350/350 no ac.
My vin is: 342571M147213

Ill do an engine rebuild in about 2 months and my car mechanic means that i have to change my gears if i want to run my combo with the best results...
He said (because im from Germany!!!) i dont go higher than 3.23 !

But what diff do i have???

So ive jacked up my baby and turned one wheel ; the other one turns to the opposite site. Ive counted 2,5 wheel turns by 1 shaft turn. its a 10 bolt.
My diff has an Tag on the bottom of the cover but i dont know (there is something like "use limited slip......" )what it means....
My cover looks like the picture below.

My question now is, What diff and what gears do i have and what does this tag means???
AND WHERE CAN I GET GEARS FOR MY REAR AXLE????

PlEASE HELP ME OUT!!!!!!!!!

THANK YOU VERY MUCH !!!
Greetings from Germany
Torsten

 

The tag on the rear means you have a posi-traction or limited slip rear differential. This is a good start and turning the wheel and counting driveshaft rotations while in neutral will give a pretty good idea of your rear gear ratio....do the test a few times. You came up with 2.5 turns with one full revolution of the wheel. That would indicate a 2.56 to 1 ratio....there may also be a number stamped on the rear axle housing. The shop manual would convert that number to the ratio you have. It also will show location of the stamp.

 

10 bolt "BOP" style.
That's a decent axle, but I think someone just put a posi tag on it, far different from having the unit inside. Bad joke.
You can purchase eaton posi units (cone style-very good item) and gears for these brand new, I have even seen them on e-bay.
The ring gear in your unit will have # stamped on them with gear tooth count (like 39/11, etc), find out what you have, lots of gears around if you want to change ratio's. 3.08 gears are really common in these, I'll bet you're close.
Gut en tag.
Jim in Phx.

 

"So ive jacked up my baby and turned one wheel ; the other one turns to the opposite site. Ive counted 2,5 wheel turns by 1 shaft turn."

If the opposite wheel turns in the same direction it most likely is a posi....if the opposite wheel turns in the reverse direction of the one you are turning it is not a posi rear.

 

I don't know if they used these in 1971 but you could look for the RPO codes on the trunk lid

It would be a "GU" code like GU2 GU3 GU4

Assuming nobody changed the rear end

Here are some:

GU1 : AXLE REAR, 2.41 RATIO

GU2 : AXLE REAR, 2.73 RATIO

GU4 : AXLE REAR, 3.08 RATIO

GU5 : AXLE REAR, 3.23 RATIO

GU6 : AXLE REAR, 3.42 RATIO

GV1 : AXLE REAR, 2.73 RATIO

GV2 : AXLE REAR, 5.83 RATIO

GV3 : AXLE REAR, 3.08 RATIO

GV4 : AXLE REAR, 3.36 RATIO

GV5 : AXLE REAR, 3.55 RATIO

GV7 : AXLE REAR, 4.11 RATIO

GV8 : AXLE REAR, 2.72 RATIO

GW2 : AXLE REAR, 2.56 RATIO

GW3 : AXLE REAR, 2.56 RATIO

GW4 : AXLE REAR, 3.31 RATIO

GW5 : AXLE REAR, 2.73 RATIO

GW6 : AXLE REAR, 3.27 RATIO

GW8 : AXLE REAR, 4.10 RATIO

GW9 : AXLE REAR, 2.93 RATIO (DUP WITH GU3)

 

so im back from my mechanic....

So ive talked **** at first, means: the two wheels turns the same direction!
:-))))
The 2.56 is correct we turned the wheel 1 time while the driveshaft turns 2.5 and some little bit....

now we couldnt find out what ring gear diam. i have ....
All his books say the 8,2 and the 8,5 gasket lookin like mine...?!?!?

Now im lookin round the world for gears.... i can found gears for the 8.2 bop but the lowest is 3.55 and for the 8.5 i could found from 3.08 till the 5s

Next week we pull of the cover, and hopefullly we find out what diameter i have...

So then
If everyone can help me, i am very pleased!!!!!!!!!!

Thanks to everyone
Greetings from Germany
Torsten

 

The rear looks like a Pontiac unit. In 1971 I believe Olds used a different rear than the one you pictured so maybe someone has swapped the rear. Also from 1968 to 1970 Olds used a 12 bolt cover rear. As for finding 308 gears you will need to see exactly what rear you have...you can look on Ebay, online junk yards, or online speed shops or post a want ad on the Oldsmobile sites.

 

That could be a 1971 8.5 buick. I just bought one of those. Look for 2 big letter A on each side of the center section right where the axle tubes go into the center section. If there are the 2 A's it is a 71 buick 8.5 rearend and it will also have the 8.5 **** on the bottom of the cast housing near the bottom of the rear cover