have a 41 plymouth, it has the stock rear end which i think has 4.13 gears. any idea what rear ends will bolt in, or require the least amount of work to put in? i'm hoping to find something with 3.50-3.73 gears.

Check with your local wrecking yard.They should have a older Hollander Exchange manual that will tell you what third members will fit and will also have a ratio chart to check the ratio.I will try and check at work today,and will repost if i find any information.
EvilDr235

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Two types of people drive old cars.Rich people because they want to and poor people because they have to.
Remember EvilDr235 has a cure for Your sixness.

The possibilities for replacing your rearend are almost limitless. However, my favorite swap is a Mopar 8 3/4 rear. The key dimension is the width of the rear from the face of the drums. This is where your wheels mount and if you're running stock wheels the dimension should be the same on both rearends. Typically you can go an inch or two wider and not have any problems with clearances. I have written a lengthy article on how to make this swap. If you contact me directly via email I'll try to dig it up and forward to you. It can be done in an afternoon, isn't hard, and ends up making your car more driveable. Charlie.

I measured the rear end housing on my '40 Ply and compared it to a chart in the book "Chrysler Performance Upgrades" by Frank Adkins. Looks like '71-'76 B-body 8 1/4 & 8 3/4 rear ends should fit with no problem. Also the same year C bodies should fit. center bolt to center bolt the dimensions are almost identical. Flange to flange depending on the application your plus or minus only about 3/4 inch. I'd recommend checking this book out for more info. Good Luck, 40 plyguy

I agree on the 8 3/4 ricky,if you go back to the mid 60s they get real narrow if you want to stuff some meats in those old fenders,ratois are 2.76 3.23 3.55 3.91 all pretty common.

Ricky;
This chart should help.



In my 1948 Plymouth P-15 I installed an 8 ¼” differential. I rebuilt the differential and installed 3.55/1 gears. It was almost a bolt up. I had to weld a couple of plates on the existing spring perches in order for the spring centering pins to line up correctly. This in effect lowered the car by ¼” and I did not want to do that so to compensate I made new rear spring shackles that are 1” longer.



I was able to use my original lower plate but I had to massage the holes a bit and put a slight angle on the U bolts.



I also replaced the shock mounting bolts as the old ones were trashed.



The installation of the differential was one of the easiest parts of building my car. Hope this information will be helpful.
Don Coatney