[poncho-mike]

I've parted out a lot of GPs over the years, mostly 428 cars.

Most of the 428 cars I dismantled had 3.23 rear ends. I live in NC, so most were open rear ends. The limited slip rear ends I've encountered were mostly out of manual transmission cars and 428HO cars.

I found a 69 GP 400 car with a 2.92 limited slip rear end. I also found a 69 428HO 4-spd car with a 3.55 limited slip.

I've seen a lot of 3.08 rear ends in the 70-72 400 cars.

Hope this helps.

Mike

[Pontiyak]

All 69 GTO/GP cars that were optioned with A/C the highest gear Pontiac put in them was 3.23 . This was irregardless of engine 400/428 in the GP. The standard GTO 400 and RA III cars were same too, but on the RAIV GTO they got 3.90 gears were standard .

If the car was not A/C and non optioned for rear gear than standard were 3.55 ratio open.
And could be optioned with 3.23 open or 2.92 open etc.
The Safe-T-Trac could be added to all ratios from 2.92, 3.23,3.55 rear ends.
But even if the Axle performance option( 3.90 gear) was ordered then it still shows the
Safe-T-Trac option on PHS.

Mike is correct the 3.08 is very common 70-72.

I would as blu bomber says look on axle for some codes of try rolling rear wheels to determine.
Ben : Do you have your PHS ?

Dave

[johnta1]

I read somewhere that it is on the Drum

It was a sticker if the rear came with that.
(some years had it, but would have to look it up for which ones)

[60man]

When all else fails you could drop the cover and count the teeth and change lube while at it.
Wipe spot off on R&P and mark a tooth with something for reference.. Done that many a time...

[Ben T.]

Hey Dave , I do have the PHS Doc. ,but it doesn't have any rear end info on it . I think the inspection cover is going to have to come off to get this solved . Thanks for the info !

Originally Posted by Pontiyak

All 69 GTO/GP cars that were optioned with A/C the highest gear Pontiac put in them was 3.23 . This was irregardless of engine 400/428 in the GP. The standard GTO 400 and RA III cars were same too, but on the RAIV GTO they got 3.90 gears were standard .

If the car was not A/C and non optioned for rear gear than standard were 3.55 ratio open.
And could be optioned with 3.23 open or 2.92 open etc.
The Safe-T-Trac could be added to all ratios from 2.92, 3.23,3.55 rear ends.
But even if the Axle performance option( 3.90 gear) was ordered then it still shows the
Safe-T-Trac option on PHS.

Mike is correct the 3.08 is very common 70-72.

I would as blu bomber says look on axle for some codes of try rolling rear wheels to determine.
Ben : Do you have your PHS ?

Dave

[Pontiac Drive]

My 70 4 speed G.P. has 3:31 ratio with a 12 bolt. Have owned several of these cars but this is the 1st one with this rear diff. All others have been 10 bolt with 3:23. Just my 2 cents.

[Pontiyak]

Originally Posted by Ben T.

Hey Dave , I do have the PHS Doc. ,but it doesn't have any rear end info on it . I think the inspection cover is going to have to come off to get this solved . Thanks for the info !

If original pig/rear still in it, I would bet 3.55 if no air . And 3.23 if has cold blowing a/c .