1949 Plymouth - P18 - More Rearend Talk

[Johnny S]

The P18 Plymouth has a rear end width of 56 inches according to the spec charts. I think the P15 is right at 60 inches. Has anyone here actually done a swap into a P18 and if so what rearend did you use? Any specific suggestions on other options? How much difference is width from stock would be ok from the safety angle? I plan on keeping the L-head.

[greg g]

Here is a chart you might find helpful. Looks like MOPAR A bodies are real close, and some fords. Advantage of these are you can retain your stock wheel bolt pattern with the ford and wit some A bodies as thes cam e in 2 sizes, the V 8 equipped cars had the same bolt patten as the rest of the line, the 6's had a smaller diameter. Remember you will need to modify your drive shaft for the newer style u joints.

http://carnut.com/specs/rear.html

[Johnny S]

Thanks Greg...that is a good chart and then an imbedded link in the chart takes you to a good description of which cars match which body style. I've searched through my files and some of the archives and haved pulled Don Coatney's photos and have some of Tim Adams photos and comments as well. So, for Tim....did you ever replace the rearend in your P18 or did you just move it and go to other projects? I also noted in the files a suggestion that someone was working on putting a new rearend into a 1950 Dodge. Did that ever come to completion or are additional photos available.

[Plymouthy Adams]

Tim here...the 50 goes back to the wider rear gear..only the 49 got the short baby..I sold my 49 as it was stock and pretty and should stay that way...had I kept it it would have gotten V power and the car deserved better than that. Don't let a couple inches scare you in rear gear installation..positive offset wheels will will cure most track width problems..Backing plate to backing plate is just one meausrement..the actual width is different for width of the drum for large brakes add to overall..track can also mess you up as the positive offset wheels come into play on advertized stance of the model car they came on..you truly need to place you intended tire on the donor axle and get the track width..experiment with offset wheels to get the track you want..then put that sucker in the car.

I have used a few different Mopar rear gears of varying width and my selection of wheels have made each and every one fit the wheel well without much ado.

I cannot say though which is best for your 49..as I did not replace that axle..I did install wheels and wire caps from a 1988 5th Ave. on it for look, modern wheel and radial tires. Drove like a champ and the new onwer elected to keep them instead of the original wheels and cap/ring setup.

[Johnny S]

Thanks Tim....that makes sense. What I read is that there may not be just one width that works correctly....it is the combination of rear end, wheel, wheel offset and brake combination that work together to give you the stance you wish. What about swapping out the u-joint at the transmission end.....are changes needed or useful at the front end of the drive line as well? I'm still thinking about swapping the rear end but possibly leaving the transmission as is or swapping for a rebuilt vintage overdrive unit.

[Plymouthy Adams]

3rd attempt to answer dial up sucks..PM me..will send comment when I return home tonight

[Guest mikeys toy]

so what would the width be for my '53 plymouth? (Don't wanna take the wheels off and screw with it in the snow)

[Johnny S]

I believe the 53 Plymouth was 55.9 inches in front and 58.4 inches in back give or take.....so about midway between the P18 and the P15. Not a dramatic difference.