An overdrive alternative

June 1, 2017 | By Staff


I am a hobbyist who has no experience with overdrives. That said, I would like to know if an overdrive could be installed to my stock 1940 Willys 440 sedan. I do not want to damage the existing stock parts. I’m asking if an overdrive could be installed by adding parts but safely removing stock parts that could be stored in the event the car would be returned to stock form. What I hope to achieve, as you may surmise, would be to allow the car to cruise without having the four-cylinder engine work so hard. Your thoughts and comments would be appreciated.


Gear Vendors in Southern California can supply an overdrive unit that you can splice into your driveshaft. It will provide overdrive, but it would mean cutting the driveshaft in half, shortening it and adding two new universal joints, as well as mounting the device. They sell in the neighborhood of $3200. If you are willing to go to that amount of work and expense, this will give you six speeds instead of three, good offthe-line acceleration and a decent top speed. They can be reached at:

Gear Vendors, Inc. 1717 North Magnolia Ave. El Cajon, CA 92020

However, a much easier and lessexpensive answer to your problem is to swap out the original 4.33:1 differential that is in the car for one that was used for other applications in the Willys line. The possible ratios, according to my sources, are the following: 4.9:1, 4.82:1, 4.7:1, 4.55.1, 4.44:1, 4.33:1, 3.73:1 and 3.54:1. I would consider switching to the 3.73:1 gear set. The 3.54:1 gearing might result in rather leisurely acceleration and problems climbing steep hills. A good source of gears and advice is:

Kaiser Willys Auto Supply 114 Bolton Court Aiken, SC 29803

Ask for Michael Meditz, the customer service guy:

This change would require nodamaging or altering of existing parts and is a relatively simple procedure. You merely pop the pumpkin and put in new ring and pinion gears with better gearing. And by the way, you cannot switch out just the ring gear because the ring and pinion gears are machined to match and must be used as a set. The car will look totally unaltered. I have swapped out differentials for better ratios in my 1958 Apache pickup and my 1940 Packard, and doing so has made a nice difference in engine rpm at cruising speeds.