How am I able to tell from numbers or codes if I have a posi rear end and are they supposed to be standard. I don't think I have one. Thanks Terry

How am I able to tell from numbers or codes if I have a posi rear end and are they supposed to be standard. I don't think I have one. Thanks Terry

Terry,there is a 2 letter code stamped on the axle housing.It will be on the LH drivers side of the axle tube and can be viewed from the back end of your car.It is usually located just below where the brake lines runs and near the tab thats holds the brake line onto the axle housing.I reccommend cleaning the area with sand paper or steel wool,then rubbing white chalk across the area and wiping the excess off to see the code better.
It would be a good idea to remove the rear cover and see what the ratio is,that is stamped on the large ring gear since your GTO is 34 years old it could have been changed and it would be a good idea to put a new cover gasket & rearend oil in it anyways!
Here is the list of rear axle codes.

41:16- 2.56 WB STND/.....YB POSI
39:14- 2.78 WC STND/.....YC POSI
41:14- 2.93 WD STND/.....YD POSI
40:13- 3.08 WE STND/.....YE POSI
42:13- 3.23 WF STND/.....N/A
37:11- 3.36 WG STND/.....ZG POSI
39:11- 3.55 WH STND/.....ZH POSI
39:09- 4.33 ..N/A...........ZL POSI
39:10- 3.90 WX STND/.....ZK POSI

(STND) STANDARD, (N/A) NOT AVAILABLE

[ September 02, 2002, 11:53 AM: Message edited by: 1-GTO ]

Terry,

Another way to tell if you have a Saf-T-Trac (Posi is for Chebby's, LOL) is to jack up the rear end so that both tires are off of the ground. With the car in neutral and the p-brake off, (make sure the front wheels are chocked) spin one of the tires. If the other tire moves in the same direction, you have a Saf-T-Trac. If it moves in the opposite direction, you don't.

To answer your other question, Saf-T-Trac is not standard on the GTO. It was an option, except with Ram Air, I believe.

[ September 01, 2002, 04:41 PM: Message edited by: GR8ONE68 ]

THIS IS MY FIRST POST! Just found this site this weekend.

Be careful with the "ole jack the wheels up" trick. I recently bought a 68 & 69 which were second party sales. Someone owned them that said they were limited slip (LSD) cars, but someone else was selling them for him and didn't think they were because the wheels spun independently and opposite of each other (I witnessed this there and when I got them home). I bought the cars as open diff-ers.

When I got them home I jacked one up to check gear ratio, removed the cover and found an LSD carrier! WOW, bonus! Did the same to the other car which was documented by PHS as Safe-T-trac and it too has an LSD. Evidently 20 years of sitting idle caused this. I just removed one of the rearends and then tilted it to drain the rest of the fluid and the axles are now spinning the same direction as they should. Hmmm, odd.

Only way to be 100% sure it's not, is to pull the cover for a visual. That's my experience. I hope that Formula I gave away wasn't one.

Kind of obvious, but the silver metal limited slip tag bolted to the rear end cover is always a good sign. To be sure though, I agree, pull the cover.