VCCA Home Forums GENERAL DISCUSSION New User Forum 1939 differential

Hi everybody, I am a new user of this forum from Québec, Canada and I need your help. Especially from Chev Nut who seem very sharp. So I bought a 1939 Chevrolet Master deluxe I bought from a Hollywood production. It just made scene for the movie Midway battle. It will be in theater in jully 2019. But I had a big loud crunchy noise comming from my transmission so I did redone entirely my transmission by myself and finaly the big noise is still there so it was a differential problem. All bearing pinion are desintegrated and so my question is: Can I swap my 4.22 ring gear and pinion for a 3.73 for a Master 85 and bolt it to the same differential. Does those ring gear have the same bolt pattern and bolt to the same master Deluxe differential? Cause I want to gain a litle more speed for RPM. Thanks to help me.

Yes, and changing to the 3.73 gears will make a big improvement for high speed driving. Both the ring gear and pinion must be used, They can be from a 1937-1939 Master leaf front spring car.
The most common is to get the unit (torque tube and rear center housing) and do the exchange. Would suggest repacing the drive shaft bushings and U joint in the process.
Your speedometer will then be 10% slow but that is easy to figure- 50 is actually 55 - 60 is 66 etc.

Thank you very much for answering. But can I keep everything and just swap the 3,73 gear instead of my 4.22 and bolt the ring gear to the same differential AND where can I find this set of gear. I look all over eBay and there is none...

You could, if you could find the ring and pinion for sale somewhere. The shop manual has the procedure. 1938 is online, and uses the same differential design. It's here: http://chevy.oldcarmanualproject.com/shop/1938/index.html

You could also probably save a lot of time and hundreds of dollars by following Chev Nut's advice.

Thank you for replying. I have aleready pull out everything cause my pinion bearings and pinion are completely destroyed. So I have to remake all of it and doing so i would like to swap now only with the ring and pinion keeping everything in place is for me the easyest way. Does someone have a 3.73 ring gear and pinion to fit a 1939 differential case to sell??

I have looked for a long time and not found a good 3.73 available. Sometimes one will come up on Ebay that is quite rusted. However the 4.22 versions are always available on Ebay and they are usually in nice shape.

And I found one 38-47 CHEVY 3.73:1 RING & PINION, could it fit??? it have the same look..

Only willl fit if it is from a 1937-1938 or 1939.

They are out there but it takes a long time to find and you need to hunt a bit. Find out the numbers stamped on the 3.73 that you mention above and then someone can check a parts book to see if it is indeed for 1937/38/39 or another year entirely.

I found my 3.73 thru Kijiji or Craigs List in California. Hot rodders usually want to sell the whole assembly. The guy used a sawzall to cut the torque tube and drive shaft leaving the pumpkin chunk intact. Easy for him and clean for me as everything is there in one package.

The correct ring gear will have part # 595022 stamped in and pinion 595021.