[tharkun8]

Hey All..

my 64 GP still has the original 3.08 open rear diff...

I picked up a nice 2.69 POSI rear axle unit from a totaled 64 Bonnie..
Im wondering if I can swap the 3.08 gears onto the POSI carrier
for the 2.69s .

Does anyone know offhand what the POSI/gear options are for the
64 units ?

thanks

John

[AZ64GP]

I believe I have something at home which lists the factory available gear ratios for the '64 GP. I'll check when I get home tonight and post a reply. I own a '64 GP myself with the 3.08, which was the standard ratio for them in '64 to my knowledge.

If all you're trying to do is determine if the 3.08 was offered with a limited slip (Pontiac actually called it is Safe-T-Track) so you can install it on your car, you're fine. It being a standard ratio, I'm sure it was offered in limited slip too. Since you're changing the ring gear anyway, maybe it's a good idea to consider if you want the 3.08 or something else too.

[rohrt]

According to my notes no this won't work.

There were 3 different ratio 8.2 Pontiac 10bolt carriers for both single track & Safe-T-Track usage
High ratio = 2.56-2.78
Mid ratio = 2.93-3.08-3.23
Low ratio = 3.36-3.55-3.90-4.11-4.33-4.56-4.88 Eaton posi for the 8.2 only in Low Ratio

I'm not sure if the safe-t-track posi was rare for High ratio but I never see them for sale. Sure would like one myself.

[tharkun8]

Thanks AZ..

my 64 GP is my Frankenstein car.. bought it as a a roller and didnt plan
on getting to it for prob 10 years.. from the production numbers I saw
i knew 3.08 seemed to be the standard gear.. but it is an open.. I got the 2.69
rear axle off of a Tboned 64 Bonnie in a local yard so it is just what was available.

My future (whenever) plan did include switching to a POSI but figured it wasnt
something I needed to think about for some time yet.

I know for 65-6s there are 3 different carriers depending on what the gear ratio is..

For now I can leave the 3.08 open.. or swap in the 2.69 POSI.. but just
wondering if the 2.69 carrier will take the 3.08 gears.. if I wanted to try that swap.
Actually, I prefer the highway gears here as I do a lot of high speed highway driving
and dont care about off-the-line for the most part. Id be happier with the 3.08 POSI
but any of the options will be ok for now.. The car literally has not moved at all under
its own power since the late 80s. so any movement here is a positive..

My plan changed when I stumbled on that 64 Bonnie here in a local Denver yard. It was
Tboned badly but it still ran and drove and was a highly optioned car.. so I raided
that car for everything.. engine.. tranny.. clear steering wheel , trunk reel out light, AC boxes
( in and out) ductwork.. etc.. Too bad the Power Stratobench was destroyed or I would have picked that up too..

I knew the car had a POSI in it but didnt buy it at the first go round.. now that powertrain
is in the GP and about to get it fired up for the first time in 30 years..

6 months later I went back to that same yard as they also had
a 67 Catalina that still had its XU 400.. so I bought the 400 and went back to look
at the Bonnie again and bought the hood and the rear axle .. which
is the reason for the question..

So soon the Darksider count will go +1...

John

[tharkun8]

Originally Posted by rohrt

According to my notes no this won't work.

There were 3 different ratio 8.2 Pontiac 10bolt carriers for both single track & Safe-T-Track usage
High ratio = 2.56-2.78
Mid ratio = 2.93-3.08-3.23
Low ratio = 3.36-3.55-3.90-4.11-4.33-4.56-4.88 Eaton posi for the 8.2 only in Low Ratio

I'm not sure if the safe-t-track posi was rare for High ratio but I never see them for sale. Sure would like one myself.

Rohrt..

Those look like the 65-6 rear numbers which is a different setup ...
64s are the last year of the front dropout type.. ( think its called a hotchkiss ?)

Though the options could still be the same..

John

[rohrt]

Originally Posted by tharkun8

Rohrt..

Those look like the 65-6 rear numbers which is a different setup ...
64s are the last year of the front dropout type.. ( think its called a hotchkiss ?)

Though the options could still be the same..

John

My bad then. My 64 A body does not have the front drop out. I didn't realize the full size cars did.

Carry on.

[hobbygto65]

B body 64 rears are 9.3" drop outs like the 9" Ford.

[tom s]

I believe the 2 gears take a diff carrier than the 3.08.3.08 go to the rare 3.31 and 3.42 goes to 5.12I think.Tom

[tharkun8]

Originally Posted by rohrt

My bad then. My 64 A body does not have the front drop out. I didn't realize the full size cars did.

Carry on.

Hey.. thanks for the attempt anyway. Believe me, Ive fallen into that
Abod/BBod difference pit too many times to count..

and it always happens when you just assume and dont bother to check

John

[tharkun8]

Just as an update...

that 64 GP fired up this AM for the first time in 30 years...

I confirmed what I suspected.. there was no 12v to the coil..
Once I jumped 12v to the coil she fired right up.. Its wasnt
unexpected because the wiring harness is a spaghetti mess
right now..

going to send a 64 block off to m+h for a new dash harness
and we can +1 Darksider !

ooo Yeah!


John

[strato gto]

9.3 rears breakdown as such: 2.56 ratio is by itself,2.69 to 3.23 is one carrier and the one you have,next is 3.42 and up.So will your 3.08 gears fit that 2.69 posi unit the answer is yes.Also I will buy that 2.69 gear set for my 3.23 posi rear 64 GP.as I want to drive the car cross country in the near future.PM me.

[tharkun8]

Originally Posted by strato gto

9.3 rears breakdown as such: 2.56 ratio is by itself,2.69 to 3.23 is one carrier and the one you have,next is 3.42 and up.So will your 3.08 gears fit that 2.69 posi unit the answer is yes.Also I will buy that 2.69 gear set for my 3.23 posi rear 64 GP.as I want to drive the car cross country in the near future.PM me.

First off.. thanks for the info.. thats what I was looking for..

As to the 2.69 gear set.. I havent decided what I was going to do with them
yet.. I actually do a lot of highway driving for my work so I am considering
just swapping that entire rear axle into the GP for at least the short term.

I want to get a good idea of the difference in rpm/gas usage. Since the
engine in the car is still an unknown quantity at this point Im also thinking
running slightly lower RPMs might be a good idea for a while..

Sorry about that. If I do decide to sell those 2.69 gears you will be first on the
list.

thanks again..

John

[strato gto]

Going from 3.08 to 2.69 will drop the Rpms about 350.Each incremental gear change is almost 200 rpm.So for my car at 70 mph,I can expect rpms to be reduced from 2875 to about 2349.Tire size also figures into this to a much less extant.Anything under 2500 rpm you can tolerate on the highway IMHO........

[PONTIAC LARRY]

Yes the 2.69 safe t track posi diff will fit your 3.08 gear. That carrier is 2.69,2.87,3.08,3.23- The next one is 3.42 up and other is 2.56 down for 57-64 9.3