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I'm helping my buddy get this old 1.5 ton cab and chassis going but the rear end is locked up and the backing plates are rotted. I've also heard that these rears are geared very very low and top speed is about 40mph. He'd like to be able to go 50-55mph without stressing out the old flathead. What are my options for swapping this rear out? Someone told me a 1970's Dodge motorhome rear will have the same wheel size (19.5") and lug pattern (5X8") but I'm afraid it may be too wide and those Dodges arent too common in the northeast. The current rear end is about 50" from backing plate to backing plate. The rear wheels have been swapped from the original widowmakers and the tires have good life so I'd like to try to keep it in the 5x8" lug pattern if possible. Any suggestions?
I think you've identified the best donor to meet the variables you've listed. The Dana 70HD's 4.56/1 final drive ratio is ideal. A Dodge RM400 or RM500 motor home D70HD axle in your area was on eBay not long ago, but I don't find it now. Below is a picture of one I had intending to do a similar conversion. I never got to it so sold the axle to a guy planning the same. Besides him I know of this swap having been done on a Studebaker 1.5 ton. I don't recall the WMS-WMS measurement of mine, but it wasn't outside a range of normal for an old truck. Below is the Dana reference for Bill of Materials (BOM) numbers.
I live in IL and found my axle in Kentucky. The Studebaker guy lives in MO. I've found quite a few and have salvaged their 19.5" Budd 89340 wheels. You'll have a hard time convincing me that old motor homes don't go to die in NH. Yards tend to hide them off to one side because they have lots of wood and junk to dispose of besides the chassis. Here's one now on CL in St.Louis. Stu
Thanks for the info Stu, very helpful info. Looks like I'm going to be on the hunt for a Dodge motorhome. The problem in New England is the yards are disappearing and the few that are left all have new junk. The old yards have been forced out by environmental laws and we are in the extreme rust belt so even when you do find something old it is often so rusted that its unusable. I'm sure I can dig one up somewhere though, I've never really been in the market for a 70's Dodge so I may have been looking right passed them, haha. Thanks for the help!
When I had my '40 1 1/2 ton truck I had a Dodge motor home rear end that I was going to install. The frame widths were the same and the bolt pattern was the same 5 on 8" but the overall width of the motor home rear end was wider than the '40. It is a good option but the duals will stick out beyond a stock flat bed. I thought it wouldn't look right but that's JMO.
That's interesting. Did you record the WMS width. Wish I had on mine, and I don't find a reference for it. Stu
Sorry, no but I do remember that it would have been a relatively simple bolt in job - the spring hangers would have bolted right up to the frame on my '40 but the over all with with the duals was just too wide.
It shows my D70HD axle measured 65" WMS-WMS which matches the width shown in this below 1946 factory chart. I have similar charts for '41 and '42 but they don't record that measurement. I guess the conclusion to draw is that not all D70HD axles from motor homes are the same width. I posted the BOM code in the old thread so hope that helps isolate a search for the right donor. Stu
Edit - here's an ebay listing for a front axle. Might contact him to see if the rear is available too. Stu
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