[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.

[mgarblik]

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.

That axle in the pic looks fantastic.! I raced a 66 2+2 with a 3.73:1 gear ratio and a 4-speed for years. Other than axle bearings and seals, never had to service anything on it. Ran those old 7" wide slicks that were available back in those days. It never failed me.

[Zooguy]

Forgive me for the slow response everybody and I do appreciate all of your comments.

Just to clarify a few things no, this isn't MY big tire big motor star chief executive project. this is my wife's 1966 Pontiac Bonneville four-door hardtop.

CURRENTLY her cars has a 1970 400 short block that is worn out with a gratuitous amount of crankcase pressure that could pass as a steam locomotive.

So, what I'm wanting to do is clean up and refresh MY 389 out of the Star Chief with a little bigger camshaft (comp cams XE250H) and put it into her Bonnie, restoring it back to an original 389 motor that doesn't resemble Thomas the train.

So with keeping the motor relatively stock but trying to improve acceleration slightly I figure the best bang for my buck is going to be gear ratio.

A few of y'all mentioned you might have something coming up for sale that would benefit me. As long as you're within about 300 mi of me (OKC) I'd be willing to come pick it up from you. If you're willing to meet me partway that could extend the range even further.

I don't necessarily NEED a limited slip differential but if that's what you have that would a POSI-tive.

I've got a fairly big laundry list of items that I need to get done with her car. Different rear gears would be nice but they're not essential ...... And if there was somebody with the desire for the factory 2.41 rear gears who has something numerically higher and wants to trade that could be arranged as well.

[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?