The Stovebolt Site Forums The Shop Area Engine Shop 3/4 ton to 1/2 ton???

Hi All,
I have a 48 - 3/4 ton that I use as a daily driver, and I was wondering about switching out the 3/4 ton axles for 1/2 ton components. Has anyone here done that? I have a 48 - 1/2 ton parts truck that has all the parts ecxcept the tourque tube. Some benifits I see are:

- I go from from 4:56 gears to 4:11 and the ability to go even higher
- I get rid of the expensive 3/4 ton huck brakes
- I get to loose the 8-hole, 15 inch safety wheels that they charge me $16.00 to repair
Some problems that I forsee are:

- The torque tube from the half ton will not swap over because the 3/4 ton has a tube from the tranny half way back to the pumpkin and then is a exposed shaft from the bearing back to the diff.
- possible spring/perch issues
- possible steering/linkage issues

I have some other options; leave things alone and enjoy, I have a 77 GMC 3/4 ton with a good running gear (unknown rearend ratio)that I could swap in, convert to bendix style brakes and aftermarket wheels (if available) and fix the 1/2 ton and use it as the daily driver.

I would be interested in any ideas or comments that the wise ones may have considering this modification. Hope others will benifit from this post.
Ralph

If you are going to do the swap, I would recommend getting a later differential with an open shaft, that would elimiate one problem..

Another option is to keep your differential, find one from a 64-72 with 4.10 gears in a 10 bolt. The carrier is a dirrect swap. I did it to mine recently, paid $100 for the differential. You can swap the entire differential, but it is 3-1/2 inches wider. With late model wheels and halfway narrow tires, it will fit. That's my long term plan. Unfortunately the setback on the later wheels is too deep, and they don't work on the front end.

You don't say, but can I assume both 48's are Chevys.

If so, the 3/4 ton is a longer wheel base than your 1/2-ton, so one of the issues you would face is determining what to do to lengthen the torque tube.

GMC did make long-wheel-base 1/2-ton trucks. I have no idea how they handled the longer length underneath, since the only one I've ever crawled under had a V-8, automatic, and 70's 4-wheel-dirve.

To swap rear axles you would either need to swap transmissions too, or convert the 3/4-ton transmission to connect to the torque tube.

I think if it were me, I'd either look for the later 3/4-ton differential, with better gears, or swap to a later axle assembly using an open driveline.

Thanks for the replies, FredT and Oldsub. Thats the main thing that scares me is the torque tube issues. The easiest thing that I could think of to do is find a way to convert the 1/2 ton differential to accept an exposed drive shaft or do a substitution as you suggested. The 3/4 tons have a torque tube halfway back to the rear and they convert to an exposed (open) shaft to the differential. You are correct that the 3/4 tons are 18 plus inches longer, but I think that the open drive shaft makes some swaps easier. I know that there are u-joints that convert the 48 to more modern diffs. I will keep driving until think this out some more. I would not like to get too radical. I like the stock look and would not like axles that are too wide. Thanks for your ideas and I look forward hearing more.
Ralph