[Zooguy]

**Update**

Turns out I was wrong The rear axle actually has 273 rear gears.

And I was lucky enough to find a NEW Never installed Tci 4l80 6 pinion planetary gear set. With a 2.97 1st gear and 1.57 second gear.

So now I'm considering leaving the rear axle alone and putting that into the transmission to give me a little better off the line acceleration but retain the highway cruisability

[kpbrown31]

Originally Posted by lust4speed

Almost everything is available to rebuild the big car rearend. I just received $340 worth of parts from Dave at Fab Craft which included new bearings, seals, gaskets and other parts for building a spare '65 big car limited slip rear. Anyway, Fab Craft is alive and well and they have become my only source for the big car rearend parts. No worries when ordering from them because everything will be correct for the big Pontiac. Summit, Jegs, Rock Auto and other retailers will try and sell you either BOP 8.2 parts or Chevy 12-bolt parts. Even Yukon and US Gear don't seem to have a clue that their catalogs are totally wrong. Dave's prices are decent and you won't be receiving a bunch of parts that don't fit. He hasn't made another batch of the 3.55 gears, but is compiling a list of interested people. I have a set from the first run in the '65 Cat wagon and they are excellent.

I think the GP confusion might be because of the 1969 and later Grand Prix's dropped down to the A-body chassis and share underpinnings with the GTO. I mix suspension parts and rear ends between the '65 & 66 Catalina, Bonneville, Grand Prix, and Vista models. I've also used carriers, axles, and other pieces from the 1967/1969 big cars. I can't comment on the brackets because the '67 and later use a different diameter spring perch and haven't had the need to experiment with the later stuff in the 65's.

The rear is quite similar to a Chevy 12-bolt with some of the internal parts being the same, and some just slightly different. Both have a 8.875" ring gear diameter (but different) and share the same clutch packs. Pontiac axles are a little beefier with 32 splines.

I spoke with Fab Craft a couple weeks ago and he doesn't know if he will even be making gear sets for our big cars in the next 2 years. He does have some rebuilding parts like you mention, but not gears. He gave me a ton of insight into the rear ends and which years/models swap in.

I'm in the same boat as the OP and have a gear swap or rear end swap somewhere in my future. I guess I never considered trying to change up gearing in the transmission vs the rear end. I guess a rear gear swap leaves you with a little more flexibility moving forward in the event you change transmissions or tear it up.

Side not...I haven't checked one over, but is there any resemblance between our 66 big Pontiacs and say a 66 Impala for a potential rear end swap. A buddy of mine has one but I've honestly never thrown a tape measure on it or even glanced under it. If a guy does swap, would a 12 bolt or Ford 9" be preferential?