1955 vs 1956 Ultramatic converter lockup.

Posted by Redhexagon On 2023/6/1 23:21:24

So, I have a question:

Did Packard change the tuning for the converter lockup for 1956?

I ask because my 1955 goes into lockup pretty quickly. During what I would call "average keeping up with traffic" acceleration under a steadily held throttle, it shifts from low to high around 20 mph, then locks the converter around 35 mph. It stays locked unless you open the throttle pretty far, I would say about 2/3. It's actually a bit annoying, because it will remain locked in direct drive even if you slow down to 25 mph then try to speed up again. It lugs hard in direct drive when you do this, unless you give it pretty hard throttle, and then sometimes rather than unlocking the converter it will downshift all the way to low in a big lurch of drama. A simple unlock would have been enough.

This contrasts to my friend's 1956 that I drove a few weeks ago. His waited much longer to lockup while accelerating. You almost had let off the throttle to cease accelerating and just maintain speed, and then it would lock. Just a slight press of the throttle to begin accelerating again would unlock it again. Basically, it only locked during steady state cruising or very slight acceleration. Even moderate acceleration made it unlock at speeds under about 40 mph.

All other shifts felt the same between my transmission and his.

Nothing I read in the technical papers, manuals, and service bulletins about the Twin Ultramatic mentions much about what speeds and throttle openings the lockup, or unlock, should occur.