Re: 1955 vs 1956 Ultramatic converter lockup.

Posted by Ross On 2023/6/2 6:51:45

The valve bodies were recalibrated between 55 and 56.

Your car has the throttle pressure set too low. Move the slider on the carb linkage to the rear of the car about an 1/8" at a time till the shifts come when you like. That link should be in the upper hole on the cross shaft on a 55. You might then run into the the problem of unwanted kickdown to low when all you really want is come out of direct. That was alleviated by an "extension kit" that made the lever on the cross shaft a little longer to reduce the rise of throttle pressure when you tromped it.

But there is technique also: The TUs are designed to be quite responsive to what you do with your foot. If you want to come out of direct, don't just tromp down slowly, I can guarantee you will get low. A quick short motion of the foot will give you direct.

Your friend's 56 has the throttle pressure set too high. His link should be in the middle hole and the slider moved slight forward to achieve an earlier lockup. In my opinion they made the l-h shift in 56 a little too late so that at light throttle the l-h and direct shift run close together.