How do you find out what rear end you have like if its posi or what not with out doing a burnout? Like what would the numbers be on that sticker in the compartment in the trunk the only one i reconized was LB9. The only other thing i know is its a 10 bolt. Im pretty sure its not posi but i want to know what type it is so i can find out wich gears to buy i want bigger like 3:73s.

 

if you are refering to the car in your profile (91 z28, 305, automatic) then your rear gear ratio is 2.73 only ratio available for that combo. as for the rpo code, its the one that start with "G" G80 = LSD the other "G" code which should be on your car GU2 = 2.73 gear ratio.

https://www.thirdgen.org/tech-data

 

ok so i checked and my car said g80 and you said thats LSD right. so whats the diff between LSD and Posi trac? wich is better also how do i tell if its a 3 series carrier or 2 or w/e cause i found some gears and it said needed to be a 3 series so whats taht mean?


would these froms hawks work??
http://www.hawksthirdgenparts.com/in...OD&ProdID=1252

 

LSD and POSI are the same thing.

 

well i still only get one wheel spining

 

RPO G80 Limited Slip=the slang term Posi, which is short for Chevrolets Postraction name used in the 60s which are the same thing.

Those gears can only be used with 3-series carrier and your have 2-series. There are some special thickness gears made for the 2-series. Otherwise you will need a new LSD carrier. Gear changes are not cheap with labor/parts and it is not a DIY type job.

 

well my uncle is pretty easy on prices of work done to my car that i wouldnt wanna atempt so id have to run it buy him first if hell want to do this. but i cant find any for the 2 series. do you suggest any sites to look on i couldnt find any on summit and taht was the only one on hawks. if its LSD i wonder why i still only get one wheel spinning do you guys think i should change the diff fluid? i dont know if it was ever changed, could that be the problem?

 

With the ages of our cars, it surprises me that anyone takes what the RPO codes on that car as "gospel". Either open it up, read the stampings, then cross-reference. Or easier, just jack the car up, put it in neutral, and spin the tires by hand. Count the revolutions & the pinion/driveshaft rotations=your gear.

You can also check fgor posi(lsd) at this time.

 

i cant get my car into neutral without it being on the gay thing wont move unless its on. gay automatic how would i tell if its posi by spinning the wheels? ( sorry for the noobbie questions) but i just dont know how i would tell.

 

Turn the key to ON position, BUT DO NOT START THE CAR! Press the brake pedal. No brake=no movie outta Park. Slip it into Neutral, release Brake.

IIRC, with LSD, the tires will rotate in opposite directions, and the opposite side can't be stopped by hand.

Open...I think the other side will rotate to, but easily stoppable by hand.

Either get a second pair of hands for the other side, or find something to block one side. With LSD, the opposite side won't move easily by hand, with Open, it MIGHT hang for a second, then freely spin.

 

so if both tires spin its LSD and if both spin but the other can be stoped easily its open got it. thanks

 

If only one tire spins,either you have an open diff or a worn posi.

 

if its a FULL POSI then both will turn, the same way and cannot be stopped, a LIMITED SLIP is when one goes clock-wise, the other goes counter c/w. and yes open you can just spin one side and the other can be grabbed and stopped easily while its in motion. pop your diff cover off and change the fluid, while your in there you can either look for a STAMPING on the gear to tell you what the gears are OR count your ring gear, count your pinion gear and then DIVIDE it and youll get your number. i did mine and it came out 3.45454545454545 which is 3.45 gears, it was also stamped on there (get a rag and wipe it) posi tracs can be defective if the rear diff oil's are bad and dirty. just change it anyways and get yourself a new gasket and use some RTV to seal er up good. anything else?

 

theres no such thing as "full posi" posi is short for positraction, which was chevy's trademark for a clutch-type limited slip differental in 8.5 10 bolt and 12 bolt rear in the 60's and 70's

 

Couldn't agree more. Change the fluid and 'see' whether you have LSD or not. Then check the stampings on the ring and pinion:

41 : 15 = 2.73
41 : 14 = 2.93
40 : 13 = 3.08
42 : 13 = 3.23
41 : 12 = 3.42
41 : 11 = 3.73

JamesC

 

allright ill do that today thanks for all the help. And i jaked her up yesturday and both tires spun the same way and i couldnt stop the other (of course i was the only one trying had no help) but the other tire did not just spin it stop when the other stopped.