Re: Twin ultramatic shifting?

Posted by HH56 On 2017/11/12 17:45:17

The Twin Ultra was a revision of the original single speed no shift Ultramatic used thru late 54. That transmission started and stayed in either high or low range depending on operator selection and made no shifts. It had one transition to direct drive to lock up the torque converter at a speed depending on throttle opening. The late 54 Gear Start and the later renamed 55-6 Twin Ultramatic kept that function but also added a range where the car would start in low, shift to high and then do the direct drive transition. In 55 the triangle to the left of D is the original start in high then direct drive operation and the triangle to the right of D is the start in low, shift to high, then direct drive operation.

The shift points really can vary due to running changes. 55s had an improved shift pattern from 54 gear starts and was changed again for 56 but a lot of 55s were upgraded to more closely match the 56 pattern. The throttle pressure adjustment also has a lot to do with the shift points and, as the Twin Ultra was still in a learning and formative stage during the short two year production other mods have been devised over the years since Packard went away to also change and improve the shift. It is really hard to say if your car might have none, any or all of the various changes.

Packard did issue a guide for the 55 pattern after the car was in production a short time but that changed with varying mods during the 55-56 years. For what it's worth here is more or less what to expect assuming your car has not had any of the later revisions.https://www.packardinfo.com/xoops/html/downloads/STB/55T-6.pdf