VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 1938 Chevy Master Ring & Pinion gears

Ok, first off, I know this has been discussed before. Sometimes it takes me a little longer to figure things out.

I have a 1938 Chevrolet Master 4 door sedan. It still has the stock 216, stock 3 speed transmission, stock rear end, and 600x16 tires. It seems like the best I can do on the freeway is about 45mph.

Everything I read says my Master has the 3.73 gears, but it doesn't seem like it when I'm driving on the freeway. How can I confirm that I actually have the 3.73 gears, and not the 4.11 gears (maybe it was changed out in the restoration)?

I see that Patrick's sells the sets of 3.55 gears. Would it be worth it to switch from 3.73 to 3.55?

If you have the MD 4.22 gears you're only running about 2300 RPM at 45. With the 3.73 you'll be running about 2700-2800 at 60 MPH. <CLICK> I normally drive my '38 at about 50-55 MPH but have been as high as 65 for several miles with no issues. The time @ 65 was a short stent on an interstate. My normal 50-55 is for fuel economy reasons. The old 216 really sucks the gas when I get over 55.

Hi Tiny,

At what point do you say it isn't a gear problem and look at timing, compression, and carb settings? 45 MPH seems very slow!!!

Also what is the history of the car Modiol? How long have you had it, and what work has been done through the years?

Good luck, Mike

I've had the car about two years. It was restored when I got it. I don't know how old the restoration is. I've converted it to 12 volt and installed the pertronix kit in the distributor. It seems to run fine, just not the fastest in the group.

Modial,

My opinion is that the 3:73 gears would be most ideal. On the downdide you would see a increase in power needed to maintain speed going up inclines as opposed to the lower grear differential.

If you were to use a 3:55 it may prove too tall a gear for the engine. There is a diminishing return the higher ratio you go.

The 3:73 would be about as good as you could expect for all-aroung driving.

In any case with a good engine a 38 should be able to run at about 70 MPH or so. The noise from the engine and air passing by the car renders anything over 45 a nuesense and thus less a joy to drive. 45 MPH is fast enough for most conditions and roads. It is usually the state minimum speed limit. You will not impede traffic and other can pass you with ease.

Enjoy the drive and let the world go by.

Charlie

BTW: Drop in a 235 (later model) or a 261 (with hydrolic lifters) if you install the 3:55 gears. With the latter engine setup you can then go as fast as you please, in any lane.

Tou can remove the differential cover and see the numbers stamped on the gears or find the stamped ID numbers on the diifferential carrier.
With either ratio the car should do at least 75 MPH IF THE SPEEDOMETER IS CORRECT.You could have the correct 3.73 rear end but the speedometer gear for a 4.22 due to some one installer a used transmission.
Place the trasmission in high gear. Push the car (get help) one full turn of the rear wheel and watch how many turns the fan blade makes. With a 3.73 it should make 3 and 3/4 turns.....with the 4.22 just over 4 turns.
Is the carburetor opening up all the way with the gas pedal floored?

I don't believe that set of gears from Patrick's will go in the 38 rearend.

I gave you incorrect information. Count the turns of the harmonic balancer and not the fan.
1037=1939 ring gear and pinions are not a direct fit with the 1940 and newer.

I looked under the hood when I got home today. It appears that the rod from the gas pedal moves about 1 - 1 1/2 inches before it engages with the pivot to the carburetor rod. This is an old picture, but can I just adjust the screw to lessen the gap?

Should be able to. In your photo it doesn't look like there's any excess play. Looks like you may also need another spring.

That picture was taken when I was replacing the head gasket. I never had a spring on there. I will get one. You can't see the gap because the other rod is hanging down, and isn't connected to the carburetor. I will get a new spring.

Hello modiol,
I have a '37 MD 4dr. sedan that had the 4:22-1 rear gears. I replaced them with a complete rear assembly from a '37 2dr. Master sedan that are 3:73-1 with the correct speedo gears in the trans.
I added a 6 volt tach to the steering column to keep an eye on the engine rpm. At 55 mph it was showing 2500 rpm.
My engine is a '38 short block with a '37 head that had been installed by the gentleman that owned the car before my uncle.
I drove it to and from Haledon, New Jersey, on Memorial weekend and did not have a single problem. It got 18 mpg both ways.
If you don't have a tach, you could add a dwell meter to the coil and switch it to rpm scale and see what the engine is doing at different speeds. It may help to determine what gear ratio you have based on tire size/rpm. I saw a chart some where that listed tire size/gear ratio/rpm.