Differential ratio for 47 P-15

[caddyman68]

The differential in my 47 P-15 is a 4.10:1 by counting turns. Does anyone know of different ratios available or later years that would fit in the housing of the 47 P-15?

Thank you.

[55 Fargo]

3.54,3.73,3.90,4.10.4.30

With an OD trans Borg and Warner R 10, 3 spd overdrive trans, this 4.10 would be great, without an OD trans, it will be busy at speeds over 50 mph.

If you cannot get yourself and OD trans, a 3.73 would be an okay bet, with taller tires, it would not be too bad at 60 mph for rpm. The 3.54 diffs, came in Chryslers, subsequently may not be as plentiful.

Of course you could swap in a modern complete diff, there are some choices available.

Diffs after 1953 or 54, have different splined axles, to the tune of 16 spline axles, as compared to the older 10 spline, but this can be dealt with too...

[Plymouthy Adams]

where did you find those listed specifically for the P15...?

[55 Fargo]

where did you find those listed specifically for the P15...?

Tim, this is what was available for 6 cylinder Mopar in Canada land for 1946-48 Chrysler built 6 cylinder cars, they should bolt into the diff housing on a stock 1946-48 Plymouth.other diff ratios in the Chrysler line up were , 3.91, 3.36, 3.58, 4.56, not sure if those were for 8 cylinder cars or not, but are listed in the 1940-48 Chrsler shop manual.

1946 Chryslers and Desotos used all of these ratios depending on wheel base, or if the car was equipped with fluid drive and 3 spd trans, or fluid drive and m5 semi-auto 4 spd trans.

P15s/D 25s in Canada quite often were equipped with either 3.73, 3.90,or 4.10, depending on geographic location and customer needs.

My Chrysler had a 4.3 diff, it was froma 1948 Chrysler 7 passenger car, I pulled a diff from a 1947 Chrysler parts coupe, it was a 3.73, it had the FD and M5 trans, go figure, it should have been a 3.54, but who knows the history of the car from dealer to me.

This is of course there is not something inherently different about P15 prodution in the USA.

I did not state in my post, that these ratios were specific to 1946-48 P15 6 cyl car., but were available for Chrysler built 6 cylinder cars, in this time period....

Edited December 8, 2010 by Rockwood

[Plymouthy Adams]

my error I had read it as only P15....the next question for him is the terrain he will be operating in..is he running stock drive train otherwise..that will dictate the gear he can really be comfortable with..

Edited December 8, 2010 by Tim Adams

[55 Fargo]

no question to available ratios but I read the question as to what was specific to the P15..

Yah, I also thought about that after I sent my last post. oh,uh,okay, maybe he means what was available to the P15 line only, now I get's it:eek:......LOL

[RobertKB]

My '48 Dodge D25 (Same as a Plymouth with some Dodge trim) has a 3.9. I have two spare ones of this ratio. I also have a 3.73 from a '54 but it requires you to make a minor modification to accept the older axles which have fewer/thicker splines. Many have done this change though.

[caddyman68]

Sorry for the confusion. I was hoping to keep the original housing and just exchange the gear set.

My brother had a 51 Cranbrook he swears he ran at 80 all the time (we were young & invinceable then).

Maybe a bit later assembly would work if the wheels bolted on & the width was the same.

Thank you.

[Young Ed]

There are 3.73 and 3.54 gear sets that will bolt into your p15 housing. I have a 3.73 in mine.