I think this unlikely that your '37 has a 3.73 ratio. I know this could be, given Plymouth made some "economy models" that year, with the 65 hp engine, versus 82 on the non-econ models. More likely your '37 has the, I believe, 4.11 ratio rear end non-econ models came from the factory with.

It is hard to get highway speed out of such a car for sustained times. If you can find a rear end from an economy model do swap it out. I drove a stock '35 Plymouth coupe a few years ago that had an economy model rear end swapped into it and it cruised pretty quietly at 68 mph for quite a spell. I put a 3.7 rear end in my '37 Chevrolet from a '37 Standard model (my Chevy originally had a 4.22 rear end) with 216 cid engine and it cruises pretty decently at 65 for long stretches. Cross your fingers that your car does have the economy rear end...then maybe you want to find a higher h.p engine for the car. Jim Leman

Hi,I have a question about rear end ratio. I have a 37 ply. 2 dr. sedan. What ratio do I need to get a little more high way speed with less r.p.m.s   I believe I have 3.73 ratio. Thanks,

Ratio was found to be 3.73, after sanding and filing crud and reverse mirror reading. Bob

Thanks for posting the photo of the location of the stamping.  Explains why I could never find it on the axle housings! 

The rear end ratio (4:1) on my '41 is stamped on the top edge of the "pumpkin".  It is hard to see, but the number is circled in the attached picture.

According to the Standard Catalogue of Chysler, available rear end ratios are (standard) 3.73:1; (overdrive) 4.10:1; and (Hy-Drive) 3.73:1.

So if you have an overdrive transmission, it should be 4.1, otherwise 3.73.

Supposed to be a little flat spot with it I believe on the right side but I've never had any luck finding them.  Easy way to tell, if you have the rear wheel jacked up, mark the tire and make a complete revolution with it---you'll need a second person to watch the driveshaft and see how many times it turns in relation to one turn of the wheel.....

Where, on the rear end, is the ratio stamped? '54 wagon. Thanks in advance, Bob.