Picking up a nice 1938 L38 with straight 8 tommorow. Id like to set it up with better highway gearing. Ill never exceed 60-65mph. So are there OD 3 speeds that will bolt up to the flathead 8? Or should I change out the rear end carrier for one with better gearing? I dont want to modify it too much, a little is fine. But no 700r4 swaps.
Ill post pics when I get it to my shop. Thanks guys.

 

I think rear end gearing is a better approach as a lot of prewar cars had gearing deep in the 4's. But I don't know where you'd find taller gearsets.

 

Thanks for the info. I wonder if other GM brands had similar rear axles that I can hunt for a carrier in the 3.2 - 3.7 range of ratios.

 

The rear center sections can be changed for a Hydra-Matic rear section .
'37 thru '47 Olds or Pontiac rear centers will bolt right in .
'48 thru '54 Olds or Pontiac centers can be installed in earlier axle housings with a few mods.
The bolt pattern is the same but the bolts are one size larger . Dorman makes a double ended stud that will allow you to bolt it up .
The '48 and up ring gear is slightly larger .
The notches in the axle housing flange have to be ground out about 1/8 inch to allow the ring gear to clear the housing .
I did this swap years ago on a '37 Pontiac with a 4.37 ratio .
I installed a center from a '54 Pontiac with Hydra-Matic with a 3.23 ratio .
The car cruised easily at 65 MPH , but if you hit a steep hill , you were looking for second gear a little sooner .

 

Thank you very much. This is the exact information I needed. I will search for a 3.23 carrier. I will post pictures of my new purchase for everyone soon. The oldest car Ive ever owned before was a 1955 Buick Special with a 264/3spd. 1938 is stepping much further back. I am very excited

 

Didn't you own a 50 Rocket 88 really briefly ? You mentioned it briefly in your video of all the cars you have owned, but the Olds was just more work than you wanted.

 

Yep. It was too far gone. And I didnt own a shop then either. Lol.

 

Thank you “phantom phixer”, this is good information for me as well with my stump pulling, three speed manual’40!

 

I installed a 3rd member from a 1950 Oldsmobile with Hydramatic trans into my 1937 L37. The original gearset is a 4:37. The '50 is 3:42, a perfect cruising gear ratio. At 65mph, RPM's are now a bit over 2500.