VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 37 thru 39 3.73 Gears

Does anyone know where I can find a 3.73 gear set for a ”˜37 thru ”˜39, GM part no 602440. Or do you have a set you’d be willing to sell?

Hi Matt,

Contact Bruce Bugay <bwbugay@aol.com> in Virginia. I am always amazed what he has!

Your part number is for a set. The 11 tooth pinion 472515 was used on various models from over multiple years. The limitation is that the ring gear was not available as a separate part. The thinking was that if the ring gear was bad you also needed a new pinion.

Otherwise you might have better luck looking for a complete rear axle from a 1937-1939 Master Coupe (GB, HB, JB). Those were the only models with the 3.73 rear. Based on the information I have all the other models those years had either 4.11's or 4.22's.

The good/bad news is that a lot of those Master Coupes have been converted to street rods with an open drive shaft rear end. You never know who has the old rear axle sitting around.

There should be lots of those sets floating around the US. They were pretty common. We all got the 4.22 up here so have to import the 3.73. It's the matching speedo gears that are harder to find.

Just gathering up my spare axle parts before the snow becomes permanent and getting them into the garage. Somehow I managed to get a complete axle/torque tube assembly over a wood fence and tucked into a corner by myself and now I have to get it out. These parts always seem lighter/smaller when they are a fresh score and gain weight as you drag them about over the years.

What ratio do you have Rusty?

Hi Tim,

So winter has come to Edmonton! We are still having some fall type days but cooler than normal.

My car is a Master Coupe so it has the 3.73 gear set. It really runs well in the 60 - 65 mph range. 70 is okay but I wonder how hard that is on the original Babbitt bearings with the cast iron pistons.

It is quite a project (and $) to change a '37 to '39 rear to 3.55 gears and the gain is only about 5%. Not worth it from my perspective.

Thought you had 3.73's. I was near Edmonton yesterday picking up an orphan coupe door (spares are good!) but live closest to Calgary.
Read all the posts and arguments and trust Gene's opinion of the 3.73's being perfect so I have 3.73's to put in mine over the winter. Is your bottom end decent?

MattD, you should post an ad in the parts wanted Forum. Local sellers thru Craigslist, etc are also useful as they are often rodders looking to clean the garage and can be had cheaply.

Thanks everyone for all the replies, but I’m finding these 3.73 gear sets or the complete rearend are becoming rare as hen’s teeth. Oh well, I’ll keep looking.

Hi Tim,

I think you will be pleased with the 3.73 gear set. Given today's roads I would agree that a 3.55 might be a little better especially for road work. At least half my driving is in town with plenty of stop and go due to lights so the 3.73 really helps in those conditions. You definitely do not want a 4.22 or even a 4.11. By the way, my Miata has a 4.30 rear with 185/60-14's. 70 mph is over 3500 rpm!

I have had the pan off my engine twice. The first time was to check the oil pump, clean the 5/8" of sludge out of the pan ,and check/adjust bearing clearances.

The second time was to re-check the bearing clearances, especially the rear main to better control leakage. I checked everything and did adjust a few of the rods just because it was easy to do at the time.

I was pleased with how well the journals and bearings looked.

Hi Matt, also check out the G&D from time to time, thats where I found my 3.73 gear set. I have a 37MD that had the original 4.22. The 3.73 make a big difference!! Good Luck

_________________
Joe's 37

I've bought two complete rear axles with the 3.73 gears from two different hot rod shops for under $50.00, locally. They're just "junk" to those guys.

So MD's had a 4:10 or 4:22 rear gears? Any way to tell what my 37 has?

1937-1939 Master Deluxe had 4.22
1937-1938 Master.. 1939 and 1940 Master 85 had 3.73
!940-1948 all had 4.11 with 3.73 as an option.

3.73 good choice for 216 engine.
3.55 good choice is 235 engine is installed and steep hills./mountains are seldom in your driving habbits.

3.73 with 6.00X16 tires wil give 2766 RPM at 60 MPH and 4.22 3145 RPM.
3.55, 2630 RPM at 60 MPH.

Thanks

Bowtie Bob,

Would you sell one of the two 3.73 rear axles you have? And are they for ”˜37 thru ”˜39?

Thanks
Matt

Sorry, but they're already in cars now.