Change 4.11 to 3.73 ring and pinion

[Trevor Geddes]

I'm replacing my 1950 B2C 4.11 ring and pinion with a 3.73 , the problem I've got is because the new pinion is larger because of the ratio when you try to adjust the screw rings to move the crown wheel across for the back lash its making 1 screw ring screw inside its carrier and the other 1 is screwed out by quite a bit and it doesn't look right.

Has anyone made this change to their truck rear end and did you have the same problem .

[Plymouthy Adams]

I cannot say what the exact cause is other than to say that A gear ratio and B gear ratio are not interchangeable past X ratio number...I think if you look at the back but of the ring gear....there will be a need to have a different carrier involved in the exchange...but again...I am only saying this based on what I have read as notes in an interchange catalog and pointing you toward examination of the carrier...wish I could help with a definite, but can only point..sorry...

Edited January 23, 2016 by Plymouthy Adams

[Trevor Geddes]

I've considered looking at getting an 1/8 inch machined off the carrier and the face of the ring to help make the adjusting more central in the casing .

[JBNeal]

I do not know if machining parts for better fit inside the differential housing is a good idea...those should be precision matched parts so if what ya have is close to fitting then that isn't close enough, you may be weakening a critical part by machining off "excess" material.

 

additional information - Flathead Tachometer 

Edited October 19, 2019 by JBNeal
revised link

[Dozerman51]

You have the wrong Differential case for the 3.73 R&P gears, The same happens when you are swapping R&P ratio's for the 1 ton trucks. Certain ratios use one case and other ratio's use another.

[dpollo]

Similar frustrations.  I have a 50 Plymouth rear axle in my 35.  I installed  48 Desoto  3.7 -1 gears (complete set)  to replace the 3.9 that I have been running.

Much to my dismay there is no oil filler plug.    Caught the mistake early on and drilled a plug hole. One has to wonder if these running changes were improvements or did some diabolical engineer put them there just to annoy us ?

 

I  also have a 3.7 R&P gears only.  I was hoping to fit them to a carrier which had 3.9s.  I will be extra careful after reading about your problems.