Re: Is this an ultramatic overdrive adapter?

Posted by JeromeSolberg On 2023/11/2 16:48:42

That's just the standard tail shaft extension from the 1951-54 ultramatic.

That might be a cooler for 1949-50. It doesn't look like the standard 1951-54.

Before you use a cooler, you should get it tested, they can leak internally and that's bad. Max Merrit and Kanter also have rebuilt/tested ones available.

The main thing about the rear axle is the ratio.

Look in the service manual on this website, it has all the rear axles and ratios. The main thing of course is (depending also on the tires used) is the revs/mile. The revs/mile for a 1951-54 Ultramatic is usually rather low (geared low) because as essentially a single-speed transmission, you needed a high rear axle ratio, e.g. 3.54:1 so you could get some reasonable acceleration. That said, there was some variation.