I have a stock 3 speed gearbox in my 41 PT125, thinking of playing with the gear ratios and final drive but at this stage I don't know what any of the ratios are. Hoping someone can dig some numbers out for me.
Thanks Tom
I found this on the net:
Plymouth Transmissions from 1936 to 1941 had a first gear ratio of 2.57 to 1 and a second gear ratio of 1.55 t0 1` from 1936 to 1940. 1941 second gear ratio was 1.83 to 1. Third gear is 1:1.
The differential ratio in 1938 was 3.9 to 1. I don't know if the same applies to 1941. The truck differential may be a lower ratio.
Also from the net:
1941 Plymouth - taken from the Detroit - Chrysler Corporation Plymouth Passenger cars part list
3:73 (economy) 664941
3:91 (coupes) 664687
4:1 (all sedans utility and delivery sedans and Suburban) 664392
4:1 (passenger coupe) 664392
4:3 (export & convertible coupe) 664688
4:56 (special ratio) 695539
4:78 (export, limo - 18" wheels) 664689
4:89 (limo) 664604
Ken
Ken, many thanks for digging that info out for me, I tried many searches without any joy. probably try changing the diff as I have another sitting in the corner. Will check that one out to see what ratio that is first. Thanks again. Tom
You're welcome.
You can check the differential ratio in the truck.
Select neutral on the transmission and jack up one rear wheel and rotate it
two complete revolutions while watching the revolutions
of the drive shaft. If the drive shaft rotates a shade less
than four revolutions, it's probably 3.9 to 1. If a shade more
than four revolutions, it's probably a 4.1 to 1 ratio.
Of course, taking all safety precautions; block the other wheels
and use sturdy jack stands under the frame. I'm sure you knew this
but I thought I'd mention it anyway. :)
Ken
Thanks for your kind words, the rear I need to check is out of the truck, just need to make some space so that I can drag it out and put it on 3 axle stands. Currently spraying in my tiny workshop so it will have to be next week, I have 3 Plymouths I'm working on so I chop and change to keep them all moving forward. Will let you know how I get on. Tom
ps have a look on my website you soon get the picture.
Good morning Ken, got up a little early to put this one to bed. In the truck from what you have said I have a 4.1, the spare under the bench is a 3.9. I will now have to check if the 3.9 diff internals will fit into my trucks pumpkin. The fixings are different where the truck uses 2 U bolts and the 3.9 axle only uses 1 per side. The shocks position is pretty much the same. Tom