M6 in a 1935 plymouth?

[mark opa]

1st time member asking a probably stupid question, but can you use an M6 tranny in a 1935 plymouth? Looking to get better top end speed w/o going to a T5 or other tranny.

[mopar_earl]

The M6 transmission is underdriven. 4th gear is 1 to 1 same as 3rd gear on a 3spd.

Earl

Edited August 3, 2016 by mopar_earl

[William Davey]

If you're trying to reduce engine speed you'll need an overdrive transmission, but you'll probably find it easier to replace the differential gearing with a higher (lower numerical) ratio. 

[mark opa]

Thanks for the quick reply and information. Are there any other engines than the L6 that the M6 can mate up to?

[Plymouthy Adams]

you got to understand the ability of the L6 to generate the torque at the low RPM.....any change about is going to be a bit invasive and labor intensive...

[dpollo]

 I cannot think of a less suitable transmission for a 35 than the M6.    My 35 has the stock trans but I have

 

 changed the rear end for one with a 3.7 to 1 ratio from a postwar Desoto.  Works very well.

[mark opa]

Thanks so much for the info. Sound like the rear axle is the key to achieve lower rpms at higher speed. I have seen that the B-Body rear axles from 1962 to 1970 match the 35 Plymouth well and some have a 2.76 to 1 ratio. That rear axle mated with a standard 3 speed might achieve what I am looking for.

[dpollo]

2.76 would keep you in second gear all the time.    I would not go any taller than 3.54 .   I have driven a lot of these cars a lot of miles

 and I believe 3.7 will do the job.    The Business series Plymouth for '35 had this ratio, if you can find one.  I used a later housing

 to get more options.  

[Jerry Roberts]

What size is the engine in your 1935 plymouth , about 196 cubic inches ?  I don't think that you would want rear end gears of 2.76 with that engine . I have 2.94 gears with a 218 and I sure wouldn't want anything higher than that . You would need something higher than my gears . 

[mark opa]

Looks like a 3.7 is the clear choice. This forum is a great resource for a novice such as myself. Thanks to all that replied!

[Don Coatney]

There are many speed calculators available on the interweb. Pasted below is an example. Plug in the numbers and you can calculate what differential ratio is correct for the horsepower and torque curves of your engine. What is right for others may not be right for you.

 

http://www.advanced-ev.com/Calculators/TireSize/