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Hello Packard Friends
Following a transmission overhaul by a specialist, the direct drive clutch fails to release on throttle input, once it has engaged. The throttle valve and linkage seem to do the job correctly: On acceleration from standstill, the clutch will close at a speed depending on throttle opening, as it should. On mild acceleration it closes at 20-25 mph, on strong acceleration it closes at 40-45 mph. No issues there. On deceleration (roll-out) the clutch will fully open at 11 mph, as it should.
The trouble starts when decelerating to any speed above 11 mph and then trying to accelerate again. The clutch has not opened above 11 mph and it will hang on regardless of throttle opening, when acceleration is needed. This is particularly painful between 12 mph and 20 mph, when engine revs are to low for pulling ahead smoothly in direct drive. Yes, the clutch will open on kick-down, but that is even more jerky and painful during the second or two it takes for the transmission to react.
Any idea of what is wrong?
Before the overhaul, the DD clutch willingly opened on throttle input when needed at speeds above 11 mph. The overhaul addressed several internal and external leaks and a distorted lower valve housing. The Governor was deemed fault-free. Pressure tests were within specifications.
The Service Counselor 28-06 advises to enlarge the vent hole in the Governor housing, when the clutch stays closed at as low as 4 mph and the engine is stalling. This is not really the condition I have and I doubt that drilling a larger vent hole will fix the issue. But I may be wrong.
Grateful for any recommendation on this.
Cheers, Roland

Does the problem occur in both High and Low?
Did you do pressure tests while the problem is occuring? If so, what were the results?
Does your overhaul specialist have any thoughts based on his work?

I suspect the retaining pin in the direct shift valve may be missing or dislodged, or there is some other errant operation thereof.

My theory is that the direct shift valve is moving too far inward to the valve body, partially blocking the flow from the throttle valve. This, combined with leakage if the pin is misplaced, would require excessive throttle pressure (fluid volume) to disengage the direct drive clutch.

Furthermore, if the pressure readings from the governor, throttle valve, and direct clutch circuit act directly in accordance with transmission operation, then I think we can rule out a malfunctioning governor or a sticking DD clutch.

Considering your comment, I assume you replaced the entire lower valve housing?

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I don't know if this has anything to do with anything, but in reference to my future Ultramatic rebuild Howard cautions against swapping valve body parts. (Comment #25) Like humanpotatohybrid I'm guessing the distorted valve body was replaced?

Linkage adjustment for the throttle valve would seem to be the most obvious.




TBH I don't think my transmission kicks down either, and hasn't since I got my car. I'm going to pay closer attention next time I go for a drive.

Keep us posted, I'm curious to know what the fix for your issue is!

Did you see the November 7, 1949 bulletin? At that time there were 2 common causes to your issue.

packardinfo.com/xoops/html/downloads/Ultramatic_part2.pdf

He has a 54th series car, so he would have one of the 54th series valve bodies which is somewhat different than the chart shown and what they were doing in 49. BTW, even though he replaced it, these are by far the most common type, being introduced in the 23rd series (1950). The valve (3.577) has an inner spool valve (4), follower (6), and dowel pin (5).

The throttle pressure land is .388 sq .in. and the inner valve land is .141 sq. in. The dowel pin is .062 sq. in. The governor pressure land when the DD clutch is engaged is hence .326 sq. in.

Let's consider accelerating at 15-20MPH at half throttle, with DD already engaged. Throttle pressure at half throttle is about 42 PSI. The modulating valve regulates its pressure to be 52% higher than the throttle pressure: 64 PSI in this example.

At closed throttle acceleration (e.g. coasting downhill), the DD clutch should engage at about 15 MPH which is the speed that the governor pressure jumps from being vented, to 30 PSI. (Remember that the lands of both the governor and throttle sides of the valve are the same area when the DD is disengaged.)

The inner valve pushes on the dowel pin and hence gives hysteresis to that effect. We can see that in this case, the governor exerts 9.8 lbs to the left. The modulated pressure exerts 9 lbs. to the left. The throttle exerts 16.3 lbs to the right. So, we would not expect a disengagement. In fact, we can easily calculate that the "effective area" of the throttle pressure side of the valve, during the proportional range of modulated pressure, is .174 sq in. So, we would expect a throttle pressure of 1.87x the governor pressure to be required to disengage the DD clutch. For a governor pressure of 30 PSI (15 MPH), this would be 56 PSI throttle, which is full throttle.

Of course, at and beyond full throttle, the modulated pressure starts to match the pump pressure, and at kickdown position it then matches throttle pressure, for an effective throttle land area of .247. Considering this 85 PSI throttle pressure, we would expect it would overcome a governor pressure of up to 64 PSI. Considering that this is the governor pressure at 56 MPH, this result matches the prescribed "end of kickdown" speed of approx. 50 MPH.

So we can see that once the DD clutch is engaged, it will not disengage until the accelerator is pressed to the kickdown position, so this is normal operation. But then this begs the question of why this behavior was not previously observed.

As 53 noted, you can raise the throttle pressure to lessen this effect. However, I believe it is set properly as it is, and raising it significantly may result in the engagement happening at annoyingly high speeds. But, you are certainly free to adjust it to your liking even if it deviates from Packard's intention.

P.S. While I don't believe the essence of my previous comment was wrong, the pin which I referred to is very difficult to remove, so unless it happened to fall out for some reason, it's unlikely to have went astray. Instead, I believe OP is misinterpreting the designed behavior of the transmission.

P.P.S.
Actually, re-reading his post, I am concerned by this phrase: "but that is even more jerky and painful during the second or two it takes for the transmission to react." As soon as you floor the gas, the DD clutch should disengage and you will immediately hear the engine flare from normal torque converter operation. If there is a delay for the direct drive clutch itself to disengage, then there must be some problem.

Roland: you said the pressure tests were within specifications, but: if the direct drive clutch pressure falls at the same time the clutch disengages, then the direct drive valve is sticking. Perhaps the valve body was overtorqued? If the pressure falls but the clutch disengages later, then the clutch itself must be sticking somehow.

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The action in Low is normal, or at least it does not cause the problem I have in High. The engine spins fast enough to pull away from low speed, even when the DD-clutch is engaged. I need to test again in Low at what speeds the DD engages and disengages. The action of the DD-clutch is hardly noticable for me in Low.
We did pressure test while driving, testing all the conditions. The values were close to specification relative to vehicle speed / engine rpm.
The overhaul specialist claims that the DD should stay engaged at speed over 11 mph, even if throttle input relative to car speed would require it to open. I question that. I talked to the main Nordic Packard Owners Club representative who has a 54 Pacific (amongst six other Packards). On his Pacific (non-gear-start) the clutch opens when needed. He does not experience any low-rev engine stumble when pulling away from low speed.

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This is very interesting! I will check with the guy who did the work what he found. It actually was the upper valve body which was replaced. The Upper Valve Body was distorted and one or two valves had become stuck. Sorry for the confusion,I wrote this wrong on my initial post.

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Yes, we replaced the Upper Valve Body by the correct parts number. It fitted bolt-on.
Kick-Down (pedal to the floor, beyond full throttle) works on my car. Direct Drive does disengage om full Kick-Down. It will not disengage on neither light, medium or high trottle. I need to go beyond full trottle (i.e force full Kick-Down) to disengage the clutch. Very painful for the engine at low revs. The spring loaded linkage to the carb aligns properly. So does the throttle linkage to the Ultra.
If you don't have Kick-Down in your car and want it, let me know and I can give you some hints what to look at.

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Thank you for this! The bulletin describes the engine stalling condition when the DD-clutch does not open at all, or at very low speeds, like walking speed. I had this on my car during warm-up and after longer standing times before the Ultra overhaul i mentioned. After the overhaul the clutch always opens at 11 mph and the engine never stalls. The trouble is that DD does not release when I need to pull away from low speed above 11 mph