Need '65 Bonneville POSI-traction HELP!
 

Working on '65 Bonne Convertible 421 Tri-Power, THM400, 3.08 open rear end. Looking for a POSI unit and possibly a 3.42 ring and pinion. Best I can tell this is a heavy duty rear end, it has a 10 bolt cover, but it has 31 spline axles, the ring gear is 8.5", there are 12 bolts on the ring gear,and it is NOT a C-clip rear end, it has retaining plates at the ends of the axle housing. I've been poking around the aftermarket but can't come up with anything. Any ideas or what do you have for sale?

no aftermarket gears or posi available...you will have to buy parts or a complete rear and no one will prob pull a complete rear apart..

run a wanted add and see what pops up

65-70 full size Pontiac. There is a fair supply of parts out there for these used of course. Clutch plates interchange with many other Eaton style limited slip units. Gears and posi-cases are a little hard to find but out there. It's possible Fabcraft still has some ring and pinion sets for them. They used to have some in addition to the 9.3" stuff. Looked on their site. They have a 3.55 gear set listed but out of stock. Sounds like if enough interest, they will run a batch. They also have a rebuild kit for the Eaton Posi and axle bearings. The one you would still need is a limited slip case.

I recently sold a complete 65/66 3.42 posi rear for $1500.00

wow..i have 2 3.42 posi's drum to drum ive been sitting on...may be time to turn them

Only need one! Kansas is a long way from PA, but let's see what we can do. I haven't been on this forum for a LONG time but I guess there is a PM feature?

PM sent...

got it..let me kick it around, both still under cars...and they are behind 3 layers of cars..against the walls in my shop..major move to get them to the lift

Awjeez....my customer just called and said forget it! Gotta love it. Sorry man....

no worries...thats how it goes sometimes...

If I blow up the 3.42's in our 2+2 I know who to contact now. :D

Two other things, the ring gear diameter is 3.875" which is the same as a 12 bolt, but totally different and doesn't interchange. The other is the Fabcraft 3.55" ring and pinion were designed to fit a Series 3 carrier which was originally for the 2.93, 3.08, and 3.23 ratios. They said that carrier was the most plentiful so they made their gearsets to fit that unit.

I purchased the Fabcraft 3.55 gearset when they first brought them out and the box is sitting on a shelf, and just recently went back to Fabcraft and purchased a billet pinion yoke, bearing kit, and other parts. The Fabcraft guys are very friendly to talk to and will spend time answering questions. Eventually the rearend will be going in the '65 Safari wagon.

Just to get this correct, if I currently have a 3.23 gear, the Fabcraft 3.55 will fit?

Definitely call Fabcraft. The below chart contradicts the previous information and looks like it would be a series 2 carrier that is needed. Moot point until Fabcraft runs another batch of 3.55 gears. Their website doesn't state what is needed: Fabcraft Metal Works

Here's a list of the Pontiac carriers:

1965-1970 Rear End Information
Gear Set Usage By Carrier

Year Case P/N Ratios Supported Notes:
1965-69 9784645 2.29 2.41 2.56 Except Locking Differential
1965-69 9784646 3.08 2.73 2.93 Except Locking Differential
1965-69 9784647 3.23 3.42 3.55 3.73 3.90 4.11 4.33 Except Locking Differential

1965-70 9779041 2.29 2.41 2.56 Locking Differential
1965-70 9779042 2.73 2.93 3.08 Locking Differential
1965-69 9779043 3.23 3.42 3.55 3.73 3.90 4.11 Locking Differential

Heard back from Fabcraft today - Sunday. These guys are great. Here's Dave's response:

MICK

YOU ARE RIGHT ON THE MONEY WITH THE CORRECT CARRIER -- SERIES II ( WHICH WAS FOR 2.73 TO 3.08 OEM GEARS )

WE ARE HOPING TO MAKE ANOTHER RUN OF THE 3.55 GEARS AND ALSO HOPE TO HAVE A NEW POSI AS WELL SOMETIME IN THE FIRST HALF OF 2021

GLAD THAT 2020 IS ALMOST BEHIND US

BE SAFE - BE HEALTHY - HAVE A MERRY CHRISTMAS !

DAVE

I blew it on my original response (post #11) by quoting an internet site that listed the wrong split on gears for the '65 big car that tossed the 3.23 gearset into the wrong carrier group.

I’ve got two of those posi carriers (both currently sporting 2.73s). Looking forward to 3.55s...