The Stovebolt Site Forums The Shop Area Driveline swap out differential

I am looking to change my 1948 chev 1 ton with a 4.56 differential. I read in tech tips that Kip's41 changed out his 41 with a 1961 3.90 chev pickup differential then just changed the length of his drive shaft. In his tich tips he said that any 1955 thru 1962 1/2 ton units will fit. Will this also work on my 48. Thanks for any help

no, Kip's was a 'light duty' 3/4T, a different animal, your 1T will require a complete rear end change

Bill

first48,
You can swap in any 4.57 third member up to '72. As long as it
is the HO52/HO72 3/4 and 1 ton Eaton drop out type and not the Dana/Spicer.

Ghostrider:
I am new at some of this but trying to learn. Have heard third member before but not sure what part that is. Thanks

It's the center section that holds the gears, sometimes called the pumpkin or hog's head. The style of rear axle in your truck has a removable or drop out third member that bolts in to the housing, like a Ford 9 inch, if you're familiar with those.
Try googling "Eaton HO72" for a lot of reading on the subject.

The common swap for the AD 1 Tons is a pumpkin from 68 to 72 with a 4:10 ratio. The 1948 1 Ton would have come from the factory with a 5:14 ratio rearend. I did the swap on my 51 1 Ton and I amd happy with it.

truckernix,
what kind of speed does that 4;10 give you and at what rpm's. I am hopeing to get where I can get on the road at 60mph and not push the rpms to high. I have a 235 engine. Are those pumpkins from 68 to 72 10 bolt also so they will bolt right on. Just trying to cross all my t's before I start looking. Thanks

what size tires are you using?

You said that a common swap for the AD 1 ton is a pumpkin from a 68 to 72 with a 4:10 ratio. Are there other 68/72 with lower ratio. I take it the the splines will slide right in and do you know the spline count. Do you have any idea of where to get one. Thanks for your help

The only ratios available for that axle are 4.10, 4.57 and 5.14.

I am running a 235 with a 4:57 rear end. I now have the tac on the right setting and at 40 mph / 2000rpm, at 45 mph / 2200rpm, at 50 mph / 2500 and at 55 mph / 2800 rpm. I don't think I should push more than that because I don't feel I have much peddle left. Also what rpms should I run this engine at. From what I hear I can only change the third member to a 4:10. Do you know how much (mph)that will help me -- if I can find one. My tire size is 235/85R16. Thanks for all the help. I tell everyone about this site and just put my 48 chev panel in my first show and people loved it and I love driving it.

48,
if you look up your tires in "The Tire rack" they will show the Revs/mile. Multiply that figure by the rearend ratio that that will give you the RPM at 60 mph. Mine works out to 2700 and I am happy with that, with my 216. I do most of my high speed driving at 50 mph but 60 is also no problem.