Changing Gear ratio in 37 D5

[D.Pearring]

Hey everyone, I've been doing a lot of research and trying to figure out the easiest way to change my gear ratio for comfortable highway cruising in my 37 Dodge. Right now it has 4.10 gearing. I've read a few places about just changing the whole rear end and then a few have commented on just doing a gear swap.. what would I be looking for for just a gear swap that would be compatible with what I have? Thanks for any help.

[FarmerJon]

Beautiful Dodge!

 

I will look up the part numbers when I get home, but your options are :

3.91 from most plymouths, definitely '46-48

3.73 from early '50s plymouths and Dodges,

3.54 late 40s chryslers and some early '50s V8 dodges

 

I have 3.9 gears in my Plym, while it can and does run 70+ with traffic, it is not really a 'comfortable cruise'

3.73 gears would be a little better.

 

3.54 gears might be a little bit of a dog around town, unless you have hopped up the stock engine.

 

Another option would be to find a R6 or other early BW Overdrive transmission to swap in, and keep your 4.1 gears.

[D.Pearring]

7 hours ago, FarmerJon said:

Beautiful Dodge!

 

I will look up the part numbers when I get home, but your options are :

3.91 from most plymouths, definitely '46-48

3.73 from early '50s plymouths and Dodges,

3.54 late 40s chryslers and some early '50s V8 dodges

 

I have 3.9 gears in my Plym, while it can and does run 70+ with traffic, it is not really a 'comfortable cruise'

3.73 gears would be a little better.

 

3.54 gears might be a little bit of a dog around town, unless you have hopped up the stock engine.

 

Another option would be to find a R6 or other early BW Overdrive transmission to swap in, and keep your 4.1 gears.

I really appreciate it! I was hearing that the 3.73 would be best but I couldn't figure out how to find the right ones that fit.. I do have the opportunity to pick this up but I don't know much about it and fell.loke changing the gearing would be the easiest and cheapest solution 

[FarmerJon]

So changing ratio, from 4.1 to 3.73 is around a 300 rpm drop at highway speed. 

I assume the R6 has the same .7 od ratio as the r10 (I dont know much about the R6) 

It would drop your rpm by 1000. 

To me, that is much more worth it, especially if the R6 is the same length as your stock transmission ( the R10 is)

 

 

[D.Pearring]

8 hours ago, FarmerJon said:

So changing ratio, from 4.1 to 3.73 is around a 300 rpm drop at highway speed. 

I assume the R6 has the same .7 od ratio as the r10 (I dont know much about the R6) 

It would drop your rpm by 1000. 

To me, that is much more worth it, especially if the R6 is the same length as your stock transmission ( the R10 is)

 

 

That is some good information Thank you. My biggest problem is I can't find too much information on this particular R6. This one I believe is fully mechanical and doesn't have the engagement cable. I don't know if the one from the r-10 will fit and I also can't figure out when to engage/disengage it.