The Stovebolt Site Forums The Shop Area Engine Shop 9 inch diff in a 57 chevy 3100

Hi, I have a 57 3100 chevy and was wondering which 9 inch ford rear end should I be looking for. Any out of a certain model that will fit in there nicely. I have one from a 78 f-150 that I could use???

Just want your opinions on what you guys have used and what kind of work/modifications were involved. Thanks

Well the stock width of a 57 3100 rear is about 62 or 62 1/4 inches. That's a good place to start. What lug pattern do you want to run... 5 on 5.5(f*rd truck), 6 on 5.5 (chevy truck) 5 on 5, 5 on 4 3/4, 5 on 4 1/2...?

How about gears and axle splines?

The 9 inch is a good rear axle with plenty of aftermarket upgrades. It may be cheaper to order a new 9 inch to your specs, rather than rebuilding a wrecking yard one. Check out http://9inchfloater.com/. This company can outfit you with a new nine inch at any width, with any lug pattern, and disc brakes. I spec'd out a 61 inch wide, 31 spline, 6 lug on 5.5 bolt circle rear with 12 inch by 1.25 inch rotors for my 1940 gmc. This unit is much stronger than a regular 9 inch. It seems to me that most wecking yards want at least 3 bills for a rearend that needs complete overhaul. That $300 rear end will cost you $1300 before you have it installed.

Just out of curiosity, what is your reason for wanting to swap to the 9"?

My plans are to be running some serious hp in this truck. With this I wanted to go to a full floating 9 inch to take the abuse. As I'm in the early stages of building, better be safe then sorry What kind of hp do you think the stock diff can handle?

Well, red58 knows a guy that's running a very hot 427 in one, it'll pull the front wheels without any problem. I don't know if you're familar with the old Gasser class thay ran back in the '60s, but pretty much all of those cars ran the Chevy truck reaend, even in the AA/GS supercharged class. That's in exes of 1500 horses and welded spiders. Lots of late '50s and ear;y '60s stock cars ran this rear, too. The only real drawback is the C clip axle retantion, and the lack of a limited slip for it.
If you're looking to go racing, then the 9" would probably be the hot ticket, or even beter would be a Dana 60, which is a 3/4 ton+ capacity axle.

Wow! Thanks for the info. I'm still a young pup with lots to learn lol and I'm sure there must be some company out there making a limited slip for them like auburn

Eddies truck has slammed the wheels down so many time he's replaced the front bearings a number of times and broke a spindle, but still stock axles, and the rear has never had any problems

a Ford rear?? in a Chevy?? I thought it was usually the other way round

Bill

Unfortunatly, there isn't. Been searching since '94 for one. About the only game for one is to find the very rare '60-'62 Truck Positraction diff. I managed to find one, it was in a stripped truck that was a cab ad frame. A freind of mine was willing to go in one it to get the cab and chassis, I wanted the diff. As soon as the seller heard that we suspected it was a Posi (I spotted the tag) he decided not to sell the truck.

I built a 389 for my 59 jimmy. The 389 was bored and stroked out to 447 inches with tripower. I built this engine for torque and not HP. I figure it may have 340 HP with about 500 ft/lbs torque. The rear end didn't last 20 miles. This was the HO33 rear, the same you have in the 57 and it was completely overhauled before the engine swap.
The axle saddles were ripped from the axle tubes from the amount of torque applied. The tubes were shredded.

Thanks now that's what I was thinking was going to happen