64 Pontiac Grand Prix rear end in a 61 Bubbletop

[LMBRJQ 60]

Hi guys, my 61 project just has the original open wheel diff and i wanted to strengthen it up a bit. Have been offered a diff out of a 64 Pontiac Grand prix that is a pozi unit. compelte less brakes.
Dont know anything about the pontiac Grand prix or what is involved was more concerned to if it was worth the exercise and was a stronger diff? the car is a 389 powered car
Any opinions greatfully accepted
Regards
Steve

 

[tripower]

That is a great rearend 9.3 Olds/Pontiac. I have the same rear in my 61 Bel Air. The 64 housing is to wide for your car. It measures 57-7/8" flange to flange at the backing plate for a over all of 62-7/8" while your Chev rear measures 55" at the backing plate and 60" over all but, if you can find a 61 or 62 Olds rear housing they are 55-7/8" at the backing plate and 60-7/8" over all. The Pontiac Posi will bolt right into the Olds housing. The Pontiac housing has a flat spot on the ends of the axle tubes so to narrow that housing is not very practical. What I did was use a 62 Olds housing and 62 Pontiac 3:23 Posi. When the brackets were welded on the bearing cups have to be cut off anyway then welded back on after the brackets are done. This is how you make sure the housing is straight. So he just took out the 7/16' on both sides then was able to machine about a 1/4" off the ends of the axles. You can see the wear marks on the axles so you know just what you can get away with. Worked out great for me. I am using a 62' Olds 3:08 Posi in my 57' Buick as well.

 

[LMBRJQ 60]

Hey Dan, Thanks for the info. 61-62 Olds rear might be pretty hard to find over here but i will surf the net for one and see what i can find.
Have a quick question about the pinion height in relation to the axle tubes on the pontiac/Olds diff compared to the original diff.
Our 60 Impala has a 12 bolt Pozi rear in it and we have drive shaft contact with the rear tunnel. We have the car lowered and the seam under the rear of the rocker panel is 8 1/2 inches off the ground which gives us around 2 1/4 inches of travel to the bump stops but with 6 people and a bit of gear in it she hits when you go through a hollow etc.
Is the pinion on the olds/ponti lower or higher than the original. I think the 12 bolt is about 1/2-3/4 higher
Thanks again
Steve

 

[tripower]

Well my car sits pretty darn low and I don't have any issues with the driveline hitting on the tunnel and I have had it packed with full trunk for weekend trip and six people. I think the pinion on the 9.3 Olds/Pontiac would be about the same location as the original 8.2 Chevrolet used. The 9.3 is basically the same rear as the 8.2 but bigger and beefier.

 

[Kdurgin]

So you actually have a 3.23 in the Bel Air, not a 2.23 as in your signature huh? I thought you must have a really wide spread of ratios in your 6 speed tranny everytime I look at that 2.23. I knew GM made some 2.41's when they got into the overdrive trannys but had never heard of 2.23's.

 

[models916]

I would think you could get around the added width by changing wheel offset and saving a lot of money.

 

[LMBRJQ 60]

Well my car sits pretty darn low and I don't have any issues with the driveline hitting on the tunnel and I have had it packed with full trunk for weekend trip and six people. I think the pinion on the 9.3 Olds/Pontiac would be about the same location as the original 8.2 Chevrolet used. The 9.3 is basically the same rear as the 8.2 but bigger and beefier.
View attachment 18815View attachment 18816

Hi Dan, have you got a rating on your rear springs or even number of turns and wire diameter? if i loaded the 60 up like that i would hit the tunnel with the drive shaft. Might invest in some rear springs of a heavier rating and see what happens then
Steve

 

[LMBRJQ 60]

I would think you could get around the added width by changing wheel offset and saving a lot of money.

Doing some measurements at the moment to see what i can do. Still want an 8 inch rim under the rear so sorting out the offset requirements over the next couple of weeks to see what fits.
Only worry i have is if it is low and the offset too great it becomes an ass to get the wheel in and out
Steve

 

[tripower]

I would think you could get around the added width by changing wheel offset and saving a lot of money.

If you were dealing with 1" wider then yes an off set wheel would be that answer but I don't think a off set wheel is going to solve a 3" wider issue.

 

[tripower]

So you actually have a 3.23 in the Bel Air, not a 2.23 as in your signature huh? I thought you must have a really wide spread of ratios in your 6 speed tranny everytime I look at that 2.23. I knew GM made some 2.41's when they got into the overdrive trannys but had never heard of 2.23's.

Yes 3:23. Obviously I had a fat finger moment.... Thanks for bringing it to my attention.

 

[tripower]

Hi Dan, have you got a rating on your rear springs or even number of turns and wire diameter? if i loaded the 60 up like that i would hit the tunnel with the drive shaft. Might invest in some rear springs of a heavier rating and see what happens then
Steve

I used the Moog 6004 and 6033. Then I cut a 1/2 coil off the bottom then put them in and indexed the bottom of the spring so it sat in the saddle properly them marked the top of the spring where it should sit in the saddle and then cut it to fit which amounted to just short of a 1/2 a coil. So all in all I cut off about 7/8 of a coil. Did the same thing on the back springs. The springs will settle with time and figuring it will come down another 1" from where it sits in this pic. Read this thread. http://www.348-409.com/forum/index....nt-coil-spring-help-needed.19321/#post-164578

 

[models916]

That's only inch and a half on each side. Look at the Corvette wheel offset, more like 6 inches. What kind of problems would there be?

 

[tripower]

That's only inch and a half on each side. Look at the Corvette wheel offset, more like 6 inches. What kind of problems would there be?

Number one is not a Corvette. On 8" wheel you have a 5-1/2"-6" back set. It doesn't look right and is a hoaky way of dealing with the issue.

 

[Kdurgin]

I would think if you are going through the effort of prepping another housing and welding all the mounts on, cutting it to the proper width is the way to go.

 

[LMBRJQ 60]

Number one is not a Corvette. On 8" wheel you have a 5-1/2"-6" back set. It doesn't look right and is a hoaky way of dealing with the issue.

How difficult is it to get axles for these diffs if I was to narrow the Pontiac housing? Looks like Olds and Pontiac 61-62 housings are not that easy to find.
Looking at some of the pricing it is getting to the price of a Currie 9" rear for the old girl.
Just not really keen on the F type rear in the car
Then again if i stuff a head in a F type they are easy to find

 

[tripower]

I would think if you are going through the effort of prepping another housing and welding all the mounts on, cutting it to the proper width is the way to go.

I agree. The cost to narrow here is 350.00 plus axles and would be about the same cost as wheels if not less. http://fabcraftmetalworks.com/Home.html

 

[dads 409]

Steve did you get the pictures of the the 63 SS I sent you ? Just wandering if you did and what you thought.
Doug

 

[tripower]

How difficult is it to get axles for these diffs if I was to narrow the Pontiac housing? Looks like Olds and Pontiac 61-62 housings are not that easy to find.
Looking at some of the pricing it is getting to the price of a Currie 9" rear for the old girl.
Just not really keen on the F type rear in the car
Then again if i stuff a head in a F type they are easy to find

As I posted in the other thread Fabcraft has all the parts for these rears. Another housing that will work is 61 Pontiac...

 

[LMBRJQ 60]

Steve did you get the pictures of the the 63 SS I sent you ? Just wandering if you did and what you thought.
Doug

Hi Doug, Not yet
PM sent
Regards
Steve

 

[LMBRJQ 60]

I used the Moog 6004 and 6033. Then I cut a 1/2 coil off the bottom then put them in and indexed the bottom of the spring so it sat in the saddle properly them marked the top of the spring where it should sit in the saddle and then cut it to fit which amounted to just short of a 1/2 a coil. So all in all I cut off about 7/8 of a coil. Did the same thing on the back springs. The springs will settle with time and figuring it will come down another 1" from where it sits in this pic. Read this thread. http://www.348-409.com/forum/index....nt-coil-spring-help-needed.19321/#post-164578
View attachment 18822

Hey Dan, Have you got more pics of this car. It looks smashing in that color.
Steve