hey guys, this may sound familiar to what 79z28project posted for rear end help on this same thread, i'm building a camaro with a 355, 4 speed saginaw tranny, but the rear end is the stock rear end that came in the berlinettas in 1981, i'm not sure what the gearing is, but i know for a fact it isn't posi, people are telling me that it is a open differential rear end and that i'll never blow it up no matter how much power i put towards it, which i find that really hard to believe because nothing is really strong enough to withstand a ton of horsepower, it you guys could tell me things about open differential and even if something exists like that, and if anyone know what the gearing was back in 1981 for the berlinettas could you please let me know that also and what you opinion is toward if it will hold up to the rest of the drivetrain, the motor is going to be within the 315 to maybe the 375 horsepower range, maybe a little less.

 

what they mean by open differential is that it isnt posi. i had one on my 79. the thing did take a ton of abuse. it was a 3.08 gear. my car was originally a base coupe so i dont think it was the same as the berlinetta. but it was fun spinning that one tire and hearing it squeal. my car had a 350 with 300hp and 350 torque. and i constantly made that tire spin. it looked like my grandfathers head...really bald!!!! but you can put a posi rear in there. and change the gears to like a 3.73 rear. thats a real nice set up. that will take anything you throw at it. basically its invincable..

 

I think you'll have to check the numbers stamped on the forward facing passenger side axle tube. You may need to use some rags, degreaser, and razor blade to clear away 25 years of dirt and grease to read the numbers, but it can be done (I did it).



Rear Axle Codesfor 1981




PA
2.73:1

PS
2.41:1 Locking

PC
3.08:1

PT
2.56:1 Locking

PD
3.23:1

PU
2.73:1 Locking

PE
3.42:1

PV
2.41:1 Locking

PH
2.56:1

PW
3.08:1 Locking

PJ
2.41:1

PX
3.23:1 Locking

PQ
3.08:1 Locking

PY
3.42:1 Locking

info taken from http://www.nastyz28.com/camaro/camaro81.html#axle

 

Sometimes the decoding won't work out. I have pulled 2.43 gears out of 2.56 and 3.08 coded housings, from the factory. Atleast double check the code against whats actually in the housing. Pull the cover and find the tooth count on the ring gear and do the math. I'ts been my expierence that 3.73's are abit low for early 4spd Camaro's. I had that setup in my 79Z, only with the woreout stock motor, I could'nt drive it on the freeway. It's too hard on the motor. The only way you should run that gear efficiently is with a .68OD 5spd or a 6spd. I have the BW T10and 3.08's now and I still need a fith gear. Based on what I know and what I have done to customers cars at work, unless you're running 33 inch tall tires, I would suggest a 3.08 to 3.23 gear ratio. As far as the rear end gose, It will take a heave beating. But you can upgrade to 31 spline Moser axles and a Detroit Trutrac and have equal to or better than 12 bolt strength. The Trutrac is a mechanical L/S that uses helical gears, ie: no clutches to tearup or posi additive, just solid built brute strength L/S performance, but under heavy load it locks like a full locker. I put one in the front of my 3/4 ton Chevy K20 and it rocks.

 

but would the rear end that i have in their right now hold up with the power for a while, even without know exactly what the gearing is, see, heres the problem, if i were to upgrade all of the internals on it right now, it would cost me more to do that than to find a rear end for sale, the only other problem is around my area of the woods, second generation camaros are a needle in a haystack, i think i'm the second one in this area, so the parts around here are kinda scarce. anybody know anyone that is selling rear ends for camaros 1970-1981.

 

Since you are in the process of building the engine, do the research to find out the gear ratio. An engine that is built up may not work well with some gear ratios. Decide what type of driving you will be doing and make sure the engine/trans/rear ratio compliment each other. Set it up to run the engine in it's power band. It makes the car more drivable and responsive. There are still used rears out there, but be carefull. Anytime I buy a used rear end I spend the money to have the tubes checked for straightness and then welded. You never know what abuse it's had.

 

the past history of it was just basically driving it like a granny, but that was with the v6 and the 3 spd tranny, i'm now upgrading to a 355 with a 4 spd tranny, the driving that i'll be doing is just driving around and taking some corners with spinning the wheel, and occasionally the drag strip, but nothing so hardcore that i'm gunna blow it out in one day, i wanna try and conserve this rear end until i can either save up either enough money to rebuild it or just buy a new rear end.

 

The rear end in my car came from a 74 Nova with over 100K on it. It was in two other camaros my buddy had before I got it. It's never been openned or serviced in it's life. All told it has alittle over 200K on it now and is still useable, and believe me, it was not treated well. I wont lie, the internals are now junk, but it's still in service. You are building nearly the same combination as I am, only, I plan on converting to a 5spd.I think you'd be pretty happy with a 3.08 to 3.23 gear, depending on your rear tire hieght.