Gears for 1949 Plymouth

[1959olds]

While trying to locate an overdrive for a 49'Plymouth, six cylinder, 3 speed (which we haven't been able to find yet).The idea came upon us to leave the trans alone, but maybe to install higher gears in the rear-end instead. We are wanting to quit winding out so many rpm's on trips down the highway in third gear. Can we succesfully conquer the problem by swapping out gears in the rear, and if so, what ratio would we be the best with?

[carlnut50]

The differential in the Chrysler cars is the same design from 1937to at least 1956.The easy way is to change out the center section.In the south we call it the hog head.The axle gear splines are sometimes different and you can use your old ones.I had to do that putting a 1955 ply hog head in a 1937 plym.The 49 is probably a 3.90 ratio.Get a Dodge or Plym with automatic trans.It will probably be a 3.54 ratio.A 1955 6 cyl.is a 3.73.Dont go higher than 3.54 or you won't have enough power w/stock 218 engine.See what Desoto Frank says,He'll know.