Olds/Pontiac 9.3 in an A-Body?

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Sean Officer

Sean Officer

1967 Dodge Dart 270 2DHT 360 Magnum/A904
Joined
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Hey all,

I have been looking for a used 8.75 in my area for almost 3 years now with no luck. I have seen several Ford 8.8 and 9 inch swaps but I am wondering if anyone has tried an olds/pontiac 9.3? There is one not to far away for pretty cheap. It measures 43" perch to perch which is spot on for an a body and 54" flange to flange which if I have done my homework correctly is only 1 3/8 inch wider than the a-body 8.75 and 1/4 inch narrower than the B-body 8.75. Differences in width aside, anyone know of a reason I couldn't use it? I am asking because I am still new to all this and truly don't know what I don't know. I have not found much info on this rear end being put into a mopar so that makes me think there is something I am missing. Thanks for your time.
 
That was the rear end of choice back in the day. I remember the older (grampa kind of fellas) when I was young tell me that’s what they used. At 9.3, that’s big and no wonder why they said they were strong rear ends.
 
Most of them were the big GM pattern of 5" x 5" BS. The nice thing about the axles were that there was a wide enough flange to drill between the big pattern holes for whatever pattern you wished.
 
I’m not sure if those axles were used in the eight lug in the Pontiac drum and wheel setup, but that might add some complications to your rear brake choices. The axles still used a five lug bolt pattern, and then the drum had the large eight bolt stud pattern near its outer perimeter. I don’t know if there’s a standard drum that will fit those shoes and backing plate, but I doubt it. IIRC, it seems like the dragster guys of the way back era outfitted the big Olds/Pontiac rear with disc brakes.
 
Any used rear axle you buy used more than likely will require some work, at least to check it out. If it is not the right size for an A body, it will require shortening and perches moved. Why not look for a Chrysler 9 1/4 out of a dodge pickup. You could also get a axle out of a grand Cherokee although its not a high horsepower unit.
 
In the late 70's there were disc brake conversions offered for them, before that most all were run with 11 x 2 1/2 brake drums and shoes. The swap was also popular with the 55-57 BelAir guys. I ran one under my 27 Ford roadster truck and my 39 Ford Deluxe coupe way back in the 60's.
 
The one I am looking at has a 5x5 bolt pattern. I did look at fabcraft metal works in my search to see if parts were available. Guy is asking $150 for it. Says he is not sure about the gear ratio but thinks it is 2.75:1 and open so both things would have to change. Car currently has a 7.25 SureGrip with 2.94 gear ratio in it and I think it would hold up ok behind the 360 magnum/904 combo I am dropping in so long as I don't drive like I did when I was 19. The problem is I WANT to drive like I did when I was 19. =).
 
If the rear is set up properly, you'll have a hard time breaking it. I abused both of mine that I talked about in post #8 and never had any problems
 
I am ok with rebuilding one. I would actually prefer to. Hands on is how I learn best and that's what this project is about for me. The perches are correctly spaced for an a body. It is 1 3/5 inches wider flange to flange so I think that could be made up for with back spacing.
 
ch1ll said:
Any used rear axle you buy used more than likely will require some work, at least to check it out. If it is not the right size for an A body, it will require shortening and perches moved. Why not look for a Chrysler 9 1/4 out of a dodge pickup. You could also get a axle out of a grand Cherokee although its not a high horsepower unit.
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I had not thought to look for a 9.25 There is one at the same yard the 360 magnum came from. They want $450 for it. It's from a 95 Ram so it definitely would need to be shortened.
 
I know I'm not a numbers matching guy, although I was in the past. These days I build my cars to suit me, not the masses. I was roasted when I first joined about cutting up a 71 Demon 340 4 speed car. Fortunately I wasn't to blame, the car had been chopped up long before I took possession. These days the Demon is a 10 second bracket car headed to the low 9 second area really soon. My suggestion is to build it as you want it and with whatever parts you can get and afford.
 
A 9-1/4 can also outfitted with Dana-8-3/4 housing ends and custom 31 spline axles for positive axle retention.
 
I would make absolutely sure that you can get the parts you want for it, AND how much they would cost. I'm betting a lsd for it is almost unobtainable.
That said, it IS a very strong rear, lots were run with welded spiders, and as mentioned above, VERY popular in 55-57 chevys in place of that plastic toy rearend they came with.
 
Strictly from a cost/parts availability/strength standpoint, it's really hard to beat an 8.8 Ford swap. Cheap, available with good gears and lsd, disc brakes, mustang won't need shortening, explorer can be shortened cheaply, and any kind of strengthening parts are available.
 
Sean Officer said:
Hey all,

I have been looking for a used 8.75 in my area for almost 3 years now with no luck. I have seen several Ford 8.8 and 9 inch swaps but I am wondering if anyone has tried an olds/pontiac 9.3? There is one not to far away for pretty cheap. It measures 43" perch to perch which is spot on for an a body and 54" flange to flange which if I have done my homework correctly is only 1 3/8 inch wider than the a-body 8.75 and 1/4 inch narrower than the B-body 8.75. Differences in width aside, anyone know of a reason I couldn't use it? I am asking because I am still new to all this and truly don't know what I don't know. I have not found much info on this rear end being put into a mopar so that makes me think there is something I am missing. Thanks for your time.
Click to expand...
That's hot rodding! You could but I wouldn't.
 
Sean Officer said:
Just curious, why not?
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Those are old rear ends. Are any parts hard to get? They are monsters as well. Heavier than many pick up rears. Way overkill for a A body. You'll have more in it to make it work than a good Mopar or Ford rear.
You haven't looked hard or long enough for a 8-3/4. There are dozens of them for sale at Mopar car show/ swap meets. 68original a member here had a complete unit for sale a month ago. As clean as a new one. It sold for around $600. You need to keep looking. [SOLD] - 8 3/4 rear end - drum to drum
 
toolmanmike said:
Those are old rear ends. Are any parts hard to get? They are monsters as well. Heavier than many pick up rears. Way overkill for a A body. You'll have more in it to make it work than a good Mopar or Ford rear.
You haven't looked hard or long enough for a 8-3/4. There are dozens of them for sale at Mopar car show/ swap meets. 68original a member here had a complete unit for sale a month ago. As clean as a new one. It sold for around $600. You need to keep looking. [SOLD] - 8 3/4 rear end - drum to drum
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Thank you.
 
Sean Officer said:
I had not thought to look for a 9.25 There is one at the same yard the 360 magnum came from. They want $450 for it. It's from a 95 Ram so it definitely would need to be shortened.
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Thats a fair price. Does it have a sure grip in it?
 
Be aware the 9 1/4 is a strong but heavy axle. More so than a 8 3/4. Good for drag racing, not so much for road racing or autocross.
 
Pontiac "8 lug" wheels/drums have 5 "lugs" on the axle flanges-

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