Grand National Rear End

[Ridgeline]

This number is stamped on the axle housing of a rear differential from an 87 Grand National 14075742. Can anybody out there tell what it means. I've done a parts search and come up empty. I also need to know what to look for when buying an 8.5 rear end.
Thanks

 

[78MC-BBC]

not sure on the numbers on the axle but you can physically see the difference between the 7.5" and 8.5" g-body axle.

the 7.5 has two small pointed ears at the bottom of the housing, and the cover is more of an oval shape

the 8.5 has two squared off ears on the bottom of the housing and the cover is round

 

[Lawfree]

I'm installing a 8.5" rear out of a 84' Regal Turbo T That came with an open rear but the same 3:42 gear ratio as the GN. The Code you are looking for will be a group of letters & numbers stamped into the top of the axle tube itself about 5 to 6" from the center section. As was mentioned the ears on the center section are different as is the bolt spacing on the 10 Bolts.
This should help

http://www.oldsmobility.com/10bolt-tech.htm

BTW, if you are lucky enough to find a 8.5 inch rear in GN or Hurst 442 (only two that got them inc the Turbo-T) grab the drive shaft too, so you don't have to shorten the one you have with the 7.5" rear.

 

[Ridgeline]

I got some numbers off of the rear end. It has 3TP GU6 GM3 A216. Can anyone help me out? I have found that the gu6 is a 3.42 but I can't find out what the 3tp means. Any help appreciated since I have to drive a good distance if it is a posi.
Thanks

 

[creepin cutty]

how do i know what rear end i have, i have a 1986 cutlass salon, came with the 307...?
Thanks!
-Frank

 

[pontiacgp]

I got some numbers off of the rear end. It has 3TP GU6 GM3 A216. Can anyone help me out? I have found that the gu6 is a 3.42 but I can't find out what the 3tp means. Any help appreciated since I have to drive a good distance if it is a posi.
Thanks

3TP is an 8.5 open end diff which was the standard for a T type and GN....3TJ is the code for the posi

 

[Lawfree]

how do i know what rear end i have, i have a 1986 cutlass salon, came with the 307...?
Thanks!
-Frank

Your car came with a 7.5" rear. Withthe axle code you can look up the gear ratio and tell if it is a posi or not.