The Stovebolt Site Forums The Shop Area Engine Shop rear end swap

I have a 1949 Chevy 1ton 3800 can anyone tell me if there is a particular rear end, and from what model truck or vehicle I can get to replace my original 5:14:1 rear end. I would like to travel alittle faster than 40-45mph. Any help would be appreciated.

The drop-out differential can be swapped with a 4.11 from a '67-'72 3/4-ton. Run a search here, you should find a lot of info.

Thanks for the info, now for my stupid question; What is the drop out differential? Is this the smae as the carrier? I am virtually clueless to this arena.

Yes, it's the center carrier. Simple swap, disconnect the driveshaft, unbolt the axles at the hub and pull the axles out a few inches. Then unbolt the carrier, it should fall out so have a helper with a jack. Put the newer carrier in and bolt it all back together. For gaskets, tell your parts store to look up a 71 3/4 ton HO52 differential.

You need to find a differential from a 64-72 3/4 ton. Two ratios available, 4.10 and 4.57. THe 4.10 is getting a little hard to find, but they are still out there.

As Fred said, the whole carrier assembly unbolts from the axle, rather than than having the differential attached to the inside of the axle housing. It's heavy, make sure you have it well-supported before unbolting it from the axle. I've pulled one in free-fall (junkyard doesn't allow jacks), and I narrowly avoided being hurt.

The axle itself is nearly indestructible, I wouldn't worry about hurting it - and bearings and gaskets are still readily available.

I have a '47 3800 1 ton. I swapped out the 5.14 rear end with a 3.90. Got it from Randy's Ring and Pinion 800 292 1031. It is now mathmatically possible for the old truck to do 75 mph. I had it out on the highway and kept up with traffic, but the speedo doesn't register above about 53 mph.

Wilber

That 3.90 gearset may or may not be available anymore. I've heard it's out of production. It's also a LOT more expensive than a junkyard 4.11 differential. It depends on what you want and how much you're willing to spend.

If you're counting teeth to make sure you have the right rear-end, I believe it's a 4.10 (41 gear ring, 10 gear pinion). I used to think the 4.11 was just a rounding error but it has a 37 gear ring and a 9 gear pinion. I learned that here!!

I believe that the 4:10 gearset only exists in the 67 to 72 3/4 tons with automatics. Also, I have been told that the trucks have coil springs. There was another type of rearend used in these trucks that is not compatible.

Oh, if you want to go with a new gear set, they only fit the newer style carrier, that is 67 to 72.

The new ring & pinion sets fit '64-'72 differentials, IIRC.

The 4.11 gears are often found behind automatics, but they can also be found in standard shift trucks.

It's easy to tell the difference between the axles used in '67-'72 3/4-ton trucks - only the HO-x2 has a drop-out differential in a banjo axle. The others are of a more convential design.