i recentl bought a rear out of a 89 gta and i cant tell if its posi. i know stock it was but i dont know how to tell if it is now.i have the cover off and it looks kinda like a small unit with 4 gears directly across from one another and the of course the ring and pinion. no springs or anything. donno if this help but if i spin on tire the other either wont turn or goes opposite.

 

If it doesn't look like the picture below, then its an open differential.

 

looks the same but no springs in it. im thinking someone switched it with a non posi unit before i bought it...
thanks

 

You can also tell by spinning one end. If the other end spins in an opposite direction is open ended.

 

No springs = not posi

Screw all this "one tire" business, if the parts aren't in there, then .....

the parts aren't in there.

Pretty tough logic to follow, I'll admit, but you can see how it works I'm sure.

 

ok guys thanks for your help

 

Actually it sounds like a 9 bolt rear end with the 4 pinion gears and you won't be able to see springs on a 9 bolt posi because they are inside the carrier halves.

What is the gear ratio stamped on the ring gear?
How many bolts on the ring gear?

Miles

 

No springs = not posi

Screw all this "one tire" business, if the parts aren't in there, then .....

the parts aren't in there



thats not true....i found out it was a zexel torson heavy duty posi unit with helical gears instead of springs for less slip.....now all i need is 3.73's lol

 

uh, i never saw those springs in my differential when i removed the cover and yet when i lay a strip i see two black streaks behind me

 

Yup, the Zexel Torsen is a different kind of deal.... this guy won't have one though in all likelihood, they hadn't been invented when his car was built.

The 2 stripes thing isn't any kind of "proof". The only way to know for sure is to take the cover off and look. I can't tell you how many people delude themselves with that sort of thing.

 

yup i agree the two strip method isnt a good way to tell you have posi.you can make most open rears spin em both if you release enough power to the wheels all at once.{pinning it and dumping the clutch or just all out mashing it to the floor}

 

im not "deludeing" myself with anything, as far as i know all GTA's came with posi. i dont need to mash the gas either to lay two strips. are you sure the springs are exposed like that on 9 bolts? im with 88 427 Camaro on this one

 

I don't think so. But even if that's true, it doesn't necessarily mean there's a posi in it now... if it's a 9-bolt it probably is, but if its a 10-bolt, who knows... take off the cover and look, it's the only way to know for sure. Like Miles says, it's not quite as obvious with a 9-bolt, but a 92 RS most likely doesn't have one of those. My response, and GMTech's response and pic, are based on a 92 RS, which came with a 10-bolt and has about 99.999% odds it still has a 10-bolt, so 9-bolt details are irrelevant to the issue at hand... the 92 RS we gave the answer for.

 

89 GTA's came with the 9 bolt POSI. 3:27 ratio
NO SPRINGS !!!!! it's a 9-bolt !!!!

I sell shims to tighten the 9bolt posi unit. It'll work better than new.

 

it was a early 89 gta axle with a 10 bolt posi. i figuered it out that somone had put a zexel t3 carrier in it prior to me getting it.however it is a early 89 gta 10 bolt housing.....i learned alot about posi while determining this unit. there are 2 posi units that are hard to tell. zexel-no springs 9 bolts- just hard to see.

 

I highly doubt an 89 GTA came with a 10bolt.
if you said 90, sure, but not 89

 

ALL 89 GTA's with the 350 came with the 3.27 9bolt BW rear end.

Not sure about the 305 TPI's, but I KNOW the L98's had the 9bolt 3.27 posi that year.

Heck, its the only rear listed for L98 GTA's of that year.

Check out the Tech Data sheet. Look for the 89' info. Shows that GTA's either came with the 3.27's for l98/auto's, or the 3.45's for the 305TPI/manual combo.

https://www.thirdgen.org/newdesign/tech/techdb.shtml

 

yes the T5 TPI came with 3:45's BW and dual cats.
never a 10 bolt.

 

i know this topic is long dead, but hey larry, wtf is a shim?? and how/what exactly does it tighten? forgive my ignorance