Packard Forum Index » V-8 (1955-56)

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.

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.

Thank you, Ross.

My throttle linkage is adjusted as outlined in the manual, with the carburetor link in the upper hole. My car does not have the extension kit.

I tried your driving technique and found it quite effective. I see how slowly rolling into the throttle tends to keep it in direct until you get really deep into it, and then it kicks down straight to low, while giving the throttle a quick but shallow jab just unlocks the converter. I have never seen a transmission that isn't just sensitive to throttle position, but to throttle velocity as well. I wonder how they did that in the valving?

Ross

The 56

With your shift mod. Isn't it to change the shift points.

Mine. Under power it won't shift till I let off gas.

When . Going light pedal. It will shift into d d.

My converter will disengage around 10-15.mph.

The upshift on 56 was to low. And that's where slipping happened.

I found out that mine has the optional 3.54 axle ratio, so that lowers the road speeds that it shifts.

Probably a good thing considering I live in the mountains at 7000 feet. I found out by surprise that the converter locks in low range, only when the gear selector is in manual low. That's neat. Useful, too.

The Ultramatic never stops amazing me. So advanced and smart for the time.