The Stovebolt Site Forums The Shop Area Driveline '51 3600 3/4 ton rearend swap

Hey everyone new to this site and new to Chevy truck builds. So I picked up a '51 3600 and I'm thinking of replacing the rearend with a more modern swap. The existing brakes are bad and the hubs are leaking fluid. I'm also not a fan of the gear ratio. So I was reading this link https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=831208
I was wondering if anybody had a more specific answer on what rearend to purchase. I was looking for one that is pretty bolt and ride with little modifications. Would like to know what other issues are involved in the swap like driveshaft mods and such. Want to stick with drum brakes and 8 bolt lug. Looking for a 3:xxx ratio. I'm going to be taking some measurements this week like backplate to backplate,overall width/track of the rearend, axle tube diameter , and spring mount location. Is there anything else to measure? Any and all help is greatly appreciated. Thanks again.

There are no what are called highway gears for those trucks,I hear there is a 3.73 that was available in a late 60s/early 70s 3/4 ton that all you have to do is swap the center section but is hard to find. If I were to buy another one of those year of 3/4 ton trucks I would swap in a overdrive trans first.

Yeah thats why I'm talking a swap of the rearend. What trans are you talking about swaping out for? I saw one post about T-5. How compatable is that?

The Eaton HO-52 / HO-72 like your truck has was used 1947-72. 4.10:1 gears seem to be a lot more common than people think, but that is the tallest they came. Very easy swap (as mentioned) if 4.10:1 works for you (I have 4.10's in my truck). There were some aftermarket 3.90 gears made recently that were expensive and are now pretty much non-existent, as far as finding them goes. (IIRC, I think some claim that 3.90's were made by GM at some point, but I have never heard of anyone ever finding them.)

I'm by no means sure, but a later (73 and up) 14 bolt out of a cab and chassis (narrow) dually may work; some of them were 3.73:1 (BBC powered trucks, IIRC).

Yeah the more I read the more somewhat complicated this is becoming though everything I see points to the same few options. I haven't driven the truck in 2 years so when I go up this week I'll have to get it running and give it a spin. I might just see if I could get seals and redo brakes and deal with it for a few until I can get a clearer pic of what I want to do with this truck or start my parts search while I drive and enjoy it. Just stay clear of the highway. I like the ideas whitedog was throwing around. He did mention that rearend 66sub was talking about. Also the trans route also.Right now it has the 3 speed no overdrive.

Any overdrive conversion be it a T-5 or an SM319 will require a driveshaft modification for that year truck. Since it has a "partial" torque tube it will need to be converted to a full open drive shaft. As 66submarine stated there is a 410:1 rear end available (from a 67-72 truck) but that's IT. As you mentioned if everything else is worn out it may be better to replace the entire axle housing assy. Someone else may know what later model housings may fit. Any thing you use will likely require spring pad relocation & welding.
Fred

Is that really it . Maybe some cross-member mod.I would deal with that for a trans. I'm sure there is someone here in Milwaukee who does drive shafts. It seems the T-5's are pretty available. So is there a specific T-5 era to look for? Do I have to remove tranny and get some measurements?

Here is a link basically saying the same as the first link but a little more clearer, got my answer. https://www.stovebolt.com/ubbthreads/ubbthreads.php?ubb=showflat&Number=613680