will his fit my 69 GTO?

Shadetree Racing
Newbie Poster
Posts: 1
Joined: Sun Jan 11, 2015 5:27 pm

will his fit my 69 GTO?

Postby Shadetree Racing » Mon Jan 12, 2015 8:38 pm

i purchased this years ago and i am having trouble identifying the unit.
YH code on drivers tube. date code i think is G148 and series code 8783393.
it has a psi unit in it with 3:55 gears marked 71 1( after the GM.
its 35" from center spring perch to perch and 56" backing plate flange to flange.
IMG_1107.JPG

IMG_1102.JPG

IMG_1100.JPG

User avatar
monzaz
Average Poster
Posts: 819
Joined: Tue Nov 13, 2007 7:56 pm
Location: RICHFIELD, OH

Re: will his fit my 69 GTO?

Postby monzaz » Thu Jan 15, 2015 3:19 pm

Yes this is a 1968 GTO rear end and will fit all A-body GM cars from 1968-1972 55.25 Flange to flange end of the housing
It will fit 1967 Buick Olds and pontiac also as they were wider beginning in this year from the chevy rears which were still narrower. 54.25

Your date code is G (month august) 14 (day 14th) 8 (year 1968)
The YH is a POSI code... for 1967 and could have run over into 1968 era if the guys on the line were not stamping correct or the change of the stamping happened after mid year...???
THIS IS VERY POSSIBLE GOOF.

The Posi might very well be original to the housing BUT the gears are not...1971 gears would have never been in the 68 housing. :)

The 68 code according to sources on the internet which can be a bit shaky to say the least at times...:) SAY XH is the axle tube code for 68 69 70 71 72 GTO cars.

Gears APPEAR to be in good condition...But take a dial indicator and see what the back lash is on the mesh and if you have some marking compound for the pattern to see where the teeth are meshing with each other.

Posi unit can be removed and disassemble to see if it is still alive of bottomed out and needing machine work to make work again.

Cap bolts are 60 foot lbs... NO LOCK TIGHT just clean oiled threads.
Ring gear bolts are lock tightened and torqued to 60-65 ft lbs. each .

Posi unit si a SUPER DUTY pontiac 4 spider gear posi cone type auburn factory Original.

For a 3.55 gear you should have 11 -39 tooth count

Axle shafts are 28 spline bolt in axles (non c-clip) and are 60 degree spline cut.
Axles will have sealed axle [press on bearings and a in the tube housing end pressed in seal the axle will slide through and ride on the axles machined surface just in front of the bearing and wedding ring that holds the bearing tight in place on the axle.

Brakes are all the same on the A-body 67-72 era GTO so that should swap over too. 9.5 x 2 system most 64-72 and even to 77 A-bodys used this brake system size.

That should cover it
J D Race


Return to “10 Bolt Differential Questions”

Who is online

Users browsing this forum: No registered users and 1 guest