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What size axle and 3.7:1 ring and pinion - hens teeth?


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In my 1935 Plymouth PJ resides the original axle housing and gear set of 4.12:1.

 

I have read some here about DeSoto/Chrysler overdrives and other overdrive transmission conversions.  Each is a bit different and have their own installation challenges which sometimes lead to more work and changes.  Not sure that is the route I need to go.

 

What size axle is installed in the mid 1930's Plymouth/Dodge/Chrysler cars?  In my 1968 Plymouth it is widely advertised, either the 8 3/4" or the Dana 9 3/4", yet I don't find any listing for the early years.

 

Also discussed is the mid 1930's axle ratio of 3.7:1.  Is this an impossible to find gear ratio for sale used or is it currently available from aftermarket gear manufacturers?

 

The ultimate goal is to be able to cruise down a State highway at 60 MPH and the engine being happy at about 2800 RPM.

 

 

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Some people swap out complete rear axle assemblies to get the diff and brakes they want. 
 

The rear end you have is a probably 3rd member. It all comes out together. There is no axle cover on the back off the axle housing to expose the diff. 
 

Sedans generally had taller gear ratios than coupes. Coupes carried less weight, luggage and passengers. Complete 3rd members are generally available for sale used. Are you confident your ‘35 car can push a 3.73 or so rear end to 60 mph? Does the car have a 201 engine? Could be an issue. 

Edited by keithb7
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Keith,

 

Yes, the axle looks very similar to the 8 3/4" in my 1968 Plymouth, 3rd member style.  What is the ring gear size in 1935?

 

A complete 3rd member with a 3.7:1 would be a nice find.  The 201 CID in the car pulls well, so not thinking that will be a problem with the 3.7:1 ratio.

 

Finding one is another story?

 

By the way, your Chrysler video with the stalling and pushing was great!

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19 minutes ago, rrunnertexas said:

Also discussed is the mid 1930's axle ratio of 3.7:1.  Is this an impossible to find gear ratio for sale used or is it currently available from aftermarket gear manufacturers?

First step, I doubt you will find after market parts for a mopar of this year.

While a 3:73 gear was not uncommon in the 50's Not sure about the 30's.

 

Also have no ideas between the changes of a 1930's - 1950's rear end.

There are some changes in the axle splines over the years ... gotta watch that.

Then when you get preferred gear ratio .... The steering is loose and brakes do not grab.

These cars were not built for modern speeds. If you want to go faster you may want to replace rear axle, front brakes and transmission? Instead of searching for a better "old axle"

 

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My interchange only lists Mopar rear ends back to 1937.

 

Anyone with interchange  for older years.  I can not find out if newer (1937-up) will work. Odds are not real good.

 

!937 and up have many possible 3rd. member only interchangeability.

 

DJ

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I have an early Hollander interchange. That same carrier assy fits many models. I don’t see a listing for the various gear ratios though. 
 

All 35-41 Plyms with hypoid gears it seems, interchange. 
 

 

5F52AB1F-6AD3-4774-A40C-C0A31E390588.jpeg

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Above is entire carrier assy. This one below is ring gear and pinion set interchangeability. 
 

 

E370A20C-5A45-437A-B8DB-9C60D598CA1E.jpeg

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