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Hi to you all from over in UK
Some of you may be aware that I am going through issues trying to resolve my problem with the twin ultramatic gearbox in my 55 clipper
It's a long story, but the problem ihave now which is not logical is as follows
When I stop at a junction the transmission will not engage and pull away ,but if I turn the engine off and wait 30 seconds and restart the engine the transmission will then engage and I can drive on
I cannot understand what is going on
I thought that having the engine idling in drive would keep the oil pressure up from the pump making it possible to pull away so is it possible that it needs to drop the oil pressure somewhat or completely it is baffling me .
I heard a guy called Ross who is a transmission guy gets on this forum , so maybe he could help me or any other packard owner that has any ideas please
Regards Chris

G'day Chris Crowhurst,

Missed your earlier post, or would have done this sooner, to PackardInfo!

You're right, Ross is somewhat of a Guru when it comes to Ultramatics, but is also very well versed in many other aspects of Packard.

And, I invite you to include your '55 Clipper in PackardInfo's Packard Vehicle Registry.

for your very quick response for including your '55 Clipper Custom Constellation Hardtop Coupe in PackardInfo's Registry.

Chris.

Yes contact Ross

He will most likely see this and respond.

All I can say. Is . The converter is draining. Or pump is questionable.

When I had a needle bearing in place of bushing for torque converter.
..
Oil would leak out front seal. And when I started the car up. Depending how long it sat. Would take awhile for oil pressure to build up. Before it would shift.

My guess is that the sprag clutch inside the convertor is not taking up its load as you coast to a stop. If it does not grip and hold the stator turbine still, the convertor becomes remarkably inefficient and will hardly even move the car with high revs. Some how when switched off the sprags regain their grip and you can move off.

For trouble shooting purposes I assume you have tried the High, Drive and Low positions. It would be good to plumb a gage into the high range port mentioned in the sevice manual to be certain it is getting pressure when you attempt to take off in high. If you get suitable pressure there and no forward motion on takeoff, then it is almost certain the sprag clutch is not holding.

Did you check the fluid level? Also, does the oil look good (nice clear red color) and does not smell burnt?

To add detail to Ross's response, the torque converter is composed principally of a driving and driven turbine, each radially vaned. When filled with fluid and spun, the vanes push the fluid in a circular path around the turbine (rotary flow), and hence the resulting centrifugal force draws the fluid from the center to the extremity of each turbine. Whichever spins faster, the fluid has more centrifugal force, and so will drive the other; likewise, the amount of fluid transfer between the two is heavily related to the difference in their rotary speed. Generally this difference is highest on initial acceleration, so there is a great velocity of fluid flowing from the center to the extremity of the driving turbine then into the extremity of the driven one (vortex flow); however, the momentum of the rotary flow (the flow in the direction of turbine rotation) is not great, and the torque transmitted is not satisfactory by this arrangement alone. To correct this deficiency, the torque converter has two additional turbines, which combined, utilize most of the remaining energy in the vortex flow to convert it to additional torque (hence the name "torque converter"). The fluid, because of the reaction force of flying through the (first) driven turbine, actually is afterwards flowing in the opposite corkscrew direction as what could drive another turbine in the correct direction. So, it flows through a "reactor" turbine (so named because it provides a reaction force) whose blades reverse the corkscrew direction of the fluid after which it directly flows into the second turbine which, being directly connected to the first driven turbine, provides additional torque to the output shaft.

At higher car speeds the difference in rotary speeds of the two halves of the torque converter is minimal, so the effects of the reactor are not needed, and it is most beneficial overall for the reactor to spin with the other parts (with the fluid). This is why it has a sprag clutch, to automatically engage or disengage when needed. Simply put, when the reactor is needed, the fluid flow is such that it tries to turn the reactor in the locking direction, which locks up the clutch. When it is not needed, it tends to rotate in the direction opposite. If the reactor can't lock up, then the torque multiplication is minimal to negative, negative meaning that the reactor not being able to help makes the second turbine a detriment rather than a benefit to the torque output.

I imagine that the sprag clutch slips when the reactor is changing direction at velocity, but when the transmission fluid and parts settle down with the engine off, it is able to settle in a bit and grip sufficiently to get going.

Be sure your mechanic scribes the necessary areas when disassembling the converter.

Read page 2 of the manual for diagrams and more detail:https://packardinfo.com/xoops/html/downloads/servicemanual5556/Sect07_TwinUltra.pdf