rearend ratio

[P-12 Tommy]

Hey guys, got a quick question. I was under the '41 to see if I could figure out which rearend I have. I saw a flat spot on the passenger side of the diffy. It says 43 Could that be a 4.3 Not sure:confused: BTW.... 4.3 seems weird for a car with a standard 3-speed?

Tom

Edited December 28, 2009 by P-12 Tommy

[RobertKB]

It could well be. However, 4.3 was most commonly used in a car with overdrive. If your car does not have overdrive it would likely be a 4.1 as that is what is in my '38 Chrysler. If you live in a hilly area or the car came form an area like that, a 4.3 might have been installed also. My '48 has a 3.9 and my '53 has a 3.73. I also thought the ratio was stamped on the top of the differential, not the side, but I could be wrong. Hope this helps.

[Jim Yergin]

My '41 Plymouth wagon has 4.3 stamped on its differential and I believe the 4.3 ratio was confirmed on the build sheet I got from Chrysler. I always thought the wagons had that low ratio because they were intended to haul heavy loads. Overdrive was not offered in '41 but I have installed one and I am happy with the ratio. I get both quicker acceleration in regular drive and lower rpm cruising in O/D.

Jim Yergin

[Cpt.Fred]

i measured my ratio by turning the wheels and counting the rotations of the drive shaft, must be around 4.2, and that's what my manual states as the standard for 1940.

now knowing where to look on the diff housing, i'll take a scraper and scratch off some road grime, maybe there's number on my housing, too.

is there any possiblity of getting a longer ratio, like through putting the gears from a more modern diff in there?

and this overdrive you're talking about, is that the desoto one which i'v been told is rare and expensive?

[Jim Yergin]

i measured my ratio by turning the wheels and counting the rotations of the drive shaft, must be around 4.2, and that's what my manual states as the standard for 1940.

now knowing where to look on the diff housing, i'll take a scraper and scratch off some road grime, maybe there's number on my housing, too.

is there any possiblity of getting a longer ratio, like through putting the gears from a more modern diff in there?

and this overdrive you're talking about, is that the desoto one which i'v been told is rare and expensive?

There have been a number of posts on this forum in the past about using modern differentials with friendlier highway gear ratios. I only know what I have read here. You may want to do a search using the forum search function.

My overdrive came out of a 1953 Plymouth. On the main web site there is contact information for George Asche. He deals in the overdrive transmissions.

Jim Yergin

[Cpt.Fred]

thanks, i'll have a look!