I recently bought a '55 Pontiac Chieftain. It has a 427 Chev, a Turbo-400 trans, and the stock rear end. All I know for sure is that it is a non-posi unit. Is this rear end worth spending time and money on, or should I look into something like a 12-bolt or a Ford 9"? Thanks.
I mounted a drum brake (91-94) Explorer 8.8 under mine, 3:73 posi I picked up cheap. It's about an 1" narrower than stock and helped with getting bigger tires on and off. Don't have to worry about that now though, I radiused the rear 1/4"s.
The Pontiac and Olds rears were a standard choice on heavy drag cars and some rails in their day, and were about the strogest rears available then. Some time in the '50's the pumpkin was upgraded...do not remember the year, but around '55-6-?...and the later one would fit the earlier housing. Someone here is without doubt a guru on these things...
Finding a posi unit to fit the housing is not impossible, but somewhat difficult. The rear ends on those things up to 64 are stronger than dirt! Heavy as hell, big drum brakes, monster ring gear, axles strong.
56 and older Pontiacs didn't have posi, just an aftermarket side gear kit for a cheap spool. I've got an extra axle if you want a spare to throw in the trunk when it breaks LOL.
A 71-81 Camaro/Firebird 10-bolt is literally a bolt in, although it has the wrong wheel lug pattern you might be able to mess around with pickup axles to get the right one. The only later Pontiac rear that will go right in is a '57, 58-up are coil spring and would need perches, and '59-'60 are going to be too wide. Olds would work though.
I believe I read in HRM that the later pumpkin would bolt into the earlier axle housing...I think the studs around the opening had to be swapped for larger and that was about it. Any confirmation out there?
You can put the 58-64 type into the '57 housing with a little clearance work. I don't remember hearing you can put them into the '56 and back housing though.
I have totally just been at where you are at! It really depends on what you want to do to it. What are youre plans? My car avatar came to me with a stock 55 chevy rear end non possi. (It got switched before it came to Canada to the stock one from a heavy duty olds one that it ran through the 60s-80s) I ran the stock 55 rear end around for the two years and beat it a little while I was working on the car but in the end started making noise. I tried to buy the heavy duty 57 olds rear end but the guy in Ten. US wouldn't sell it. They are getting hard to come by! Especially good ones! Parts too are expensive for them! I looked at up grading the 55 rear end using just the housing and this was a possibility but it was expensive and seriously you are really limited gear wise and possi wise what you can use. So I did my homework and looked at the different possibilities. 10 bolt possi rear ends out of cars 12 bolt possi rear ends out of cars Other pre-existing modern rear ends Ford 9 inch rear ends Explorer rear ends Nine inch kits for trifive cars from various vendors In the end I ended up going with a ford nine inch rear end that a local guy built for me. He specializes in building rear ends and custom welding rear end housings. He literally took my rear end after I removed it from the car and built an identical one that fit and bolted up perfectly. I even used the original drum brakes and backing plates to save some money (they were only 2 years old and he made it so that I could use them!) PM me if you want to talk more and I will give you my phone number. I have a broken hand and it is tough to type with one right now. J
The ideal rear end would be to find a 57 Pontiac unit.They use the 9.25" ring gear and the axles are considerably larger than the 55-56.It is also the same width.Also the 57 3rd member will NOT fit into the earlier housing;it is quite a bit larger.Good luck finding one as they are very scarce now. I have a 4.56 posi unit in my 57 Safari that uses Richmond ring and pinion.I had a set of later(63)axles that would not fit it(different splines;31 I believe and the length was wrong.)I wanted to shorten them and re-spline but they weren't large enough in diameter to do so. I finally wound up buying a complete 57 rear axle assembly and put the single track 3rd member in my housing.
55chieftain, what wheel bolt pattern does the Explorer have? Also, do you have pics of the radiused quarters? Oh, and what size tires could you cram into the wheel wells before you radiused them? Thanks again.
Thanks everyone for the input. It gives me something to think about. One of the commercial rear end guys I contacted offered to build me a 9" but he didn't mention cost...Probably a lot, I'm guessing. I did determine that I definitely have the stock 3.08 rear end. I wonder how the Explorer unit would hold up behind the big block. I don't plan on doing any drag racing, but I do have a tendency to get on it now and then. The trans shifts crisply, and just driving normally, the rear tires tend to chirp when it shifts. Yikes...The guy just got back to me on the cost of the 9" - $2530 complete. That is not in the budget right now. I just bought the car, and I am low on funds.
The 55/56 housing will hold up to a fair amount of street use with street tires. But no one ever offered a posi unit for these rears. They will not accept the later 57 up style pumpkin. Bruce is off by just a couple of years, it was the 52-3-4 chucks that work in the earlier (4 housings. The 57 housing is a bolt in unit, but again very expensive to get a posi unit for as it is 29 spline. However, the 57 housing with 62-64 posi or locker rear and matching axles would do the trick. But unless you can find someone to give the items up for a reasonable price, the 9inch ford is the way to go. Just a matter of cost. You could likely do an overhausl on an entire 9 inch rear with a posi for less than the cost of a rebuilt posi center section with axles. But if you do decide to use the olds/pont set up, I recommend John Gevo at www.rearsgears.com. I have been buying selling and trading Olds/Pont rear stuff with him for years as I run the big olds/pont rear in my 55 Buick..
The 8.8 is a 4.5" bolt pattern. The perches will need moved also. I have a Gasser build thread with some pics of the 1/4's. I know the 57 Pontiac rear is peroid correct for an upgrade, but a complete rear upgraded to 31 spline axles with a 3:90 posi is going to set you back a grand easy. Specifially the rear end i'm using has 31 spline axles with c-clips. No c clip eliminators are available for this rear only the mustang. The 95-01 are rear disc and will help some hold the axle, but it's going to take quite a bit of hook and power to break these axles. The other option would be to use the 9" big bearing ends than your looking at the extra cost of custom axles too. The later model rangers also have this rear and have drum brakes which I prefer anyway. If you decide with the 8.8 get the rear end flange and bolts(12pt 12mm head) that bolt up to the pinion flange. Also the center of the x in the frame will be to be clearanced some because of the offset to the passenger side of the pinion centerline.
55chieftain - What size tires can you cram into a stock '55 wheelwell? Any advice on wheel size and backspacing?
15x7 with a 235 60 or 70 15 would be about it. 4" bs would be right in the middle (0 offset) on a 15x7 which is actually 8" wide.
I have 8'' early torque thrust with a 245x75x15 ,I think, under mine. a pain to get on, and off. different profile will make a difference also.In a 50 olds, same r/e, I welded the spiders and drove it on the street, but that was in the 50's.
The Camaro/Firebird idea is interesting. The different bolt pattern would actually be a good thing. Thanks, rustynewyorker.
I scored an axle. Only cost me a couple hours lying in the dirt and one smashed fingernail...But no money. Anyway, it's a 3.42 posi unit from an '81 Z-28. I think I done good!
By chance is this the 55 poncho out of the Gig Harbor area, two tone blue-green and white? If so, THAT'S A NICE CAR!!! Too bad you found your rear end so fast; I have a 57 Olds complete, and ready to go (if I don't slide it under my Delivery pretty soon). Butch/56sedandelivery.
The Jalopy Journal
