Packard Forum Index » Post-War (1946-54)

Topic: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

Bottom

Previous Topic

Next Topic Register To Post

« 1 (2) 3 4 5 ... 7 »

Roland Irle

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#11

Not too shy to talk

Quote:

humanpotatohybrid wrote:
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.

Hello and big thanks for the very comprehensive description of the valve actions under various conditions. I had similar discourses with my transmission specialist and he eventually concluded that the problem I have now is normal operation, i.e. a DD-clutch release requires Kick-Down. I am not so sure.
As you wrote, i also begs the question why this problem was not there before the overhaul, when the clutch would open at part throttle and completely natural depending on car speed and load. Also spoke to a '54 Pacific owner (same non-gear-start type) in the national Packard Club. He does not need Kick-Down to open the clutch on lower speeds.
The logic of hydraulic pressures and valve operations would suggest my cars problem to be "normal operation". A feature, not a bug. Still, gunning the engine for downshift every time will not hold for long. Likely, also the Packard folks back in the days would have agreed.
More thoughts very welcome!

Posted on: 9/18 4:33

1954 Panama

humanpotatohybrid

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#12

Home away from home

I would increase your throttle pressure adjustment slightly and see if it helps.

By the way, who is this Ultramatic mechanic in Sweden you are talking to?

What else changed during the rebuild? If the small parts of the direct shift valve are jammed with grime, but the valve as a whole slides back and forth, the hysteresis functionality will be lost.

Posted on: 9/18 5:06

53 Cavalier

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#13

Home away from home

Quote:

Roland Irle wrote:
Quote:

53 Cavalier wrote:
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!

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.

I had my car out for a couple of hours yesterday, about 100 miles, and I currently have, and think I always have had, the issue you're talking about. The direct drive does not disengage until the car slows to about 11 mph. From what I understand that would be the governor disengaging the direct drive. When I give it throttle the throttle valve should disengage the direct drive at lower speeds, but doesn't..........medium or heavy throttle it doesn't disengage.

I had previously adjusted my throttle linkage and valve to factory spec and the direct drive is engaging at appropriate speeds, that is around 20 mph under light acceleration and 40 mph under heavier acceleration.

Now I'm embarking on rebuilding the transmission from my parts car to do a swap in the spring so I have a fresh transmission with clutch plates made of modern materials, but I amy curious as to why my direct drive is acting the same as yours.

I tried giving it heavy throttle for several seconds in the event it was just slow to relieve pressure, and would eventually disengage, but no such luck. The direct drive just doesn't disengage until the car slows down to around 11 mph. I have not checked pressures at all, and will probably not go to the trouble with this transmission considering I'm rebuilding the other.

Posted on: 9/18 11:13

Roland Irle

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#14

Not too shy to talk

Cordial thanks to Humanpotatohybrid and Cavalier 53 for your replies. Very sobering to hear that the 53 basically behaves in the same akward manner as mine. If this is "normal operation", than it is no wonder that Packard only sold 30 000 cars in 1954. Wait with the rebuild until we have solved the enigma, if we can.
I actually have diverted from the shop manual pocedure for adjusting the throttle valve lever at the rear right side of the transmission. I adjusted the throttle valve lever about 20 deg further to the rear than specified in the shop manual. In this position the hole in the lever will not align with the fork at the lower end of the relay rod when the throttle valve lever is at its rear stop. The lever needs to be pulled forward ca 20 deg to fit the clevis pin . This means that the throttle valve is somewhat open at idle. This way, the valve supplies pressure earlier and restricts pressure later than with the position specified in the shop manual. The effect is that the lock-up occurs 10 mph later on acceleration, 30-35 mph at light load (not really desired) and opens earlier, at 16 mph (vs 11 mph) at roll-out, which is better, but not good enough. DD will still not open when I try to accelerate at 17 mph.
Thus, cheating the clutch control valve by some pre-opening of the throttle valve somewhat improves driveability but does not solve the fundamental problem: Closing and opening of the lock-up should be variable, depending on car/engine speed and engine load. Not just depending on engine speed and brutal Kick-Downs if engine speed is too low.
The transmision specialist in Sweden is PS Maskin in Ucklum, Per Svensson, a very recommended and dedicated mechanic. I trust him, but in this paticular case his wisdom ended.
Again, looking forward to more wisdom ...
Cheers, R

Posted on: 9/18 13:47

1954 Panama

humanpotatohybrid

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#15

Home away from home

Roland, good to hear you were able to make the adjustment, but as you can see it has the expected side effects and doesn't fix the problem. What I would suggest you try is to get in the habit where, if you want the direct drive clutch to disengage, quickly press the accelerator pedal to the floor just long enough that the transmission disengages the clutch, then release it most of the way. With some practice, I think you will be able to do this to get out of direct drive, without having a dramatic response from the engine. If you find success with this, you may also be able to adjust the throttle linkage back to the usual position, so that direct drive engages earlier.

I have spoken with other drivers, the other option is to simply not hit the gas too hard, and the engine will sound a little happier. Obvious suggestion, I know.

By the way, here is a photo of the valve in question, which will complement my explanation below.

P.S. I think your transmission mechanic has quite good knowledge on these, compared to most Packard owners or old car mechanics that do not specialize in Packard.

Attach file:

20240918_002716.jpg (610.33 KB)

Posted on: 9/19 7:06

humanpotatohybrid

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#16

Home away from home

Roland, I just spoke with Ross (one of the main Ultramatic mechanics in the USA) abiut this concern. Did your mechanic need to replace the direct drive clutch from the old one being too hard? If so, then there is your answer: the reason it would have felt like it was entering converter drive before, is that your clutch was just slipping.

Posted on: 9/19 7:41

Packard Don

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#17

Home away from home

Quote:

I had similar discourses with my transmission specialist and he eventually concluded that the problem I have now is normal operation

I can tell you that from many, many years of driving Packards with Ultramatic, what you described is not normal!

Posted on: 9/19 15:43

All generalities are false.

Don Pierson
Packard / IMPERIAL page
CA DMV Licensed Vehicle VIN Verification

1951 Henney-Packard 3-Door Long Wheelbase Air Force Ambulance
1954 Packard Patrician
1954 Packard Patrician Parts Car
1956 Clipper Custom Sedan

humanpotatohybrid

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#18

Home away from home

Can you elaborate??

Posted on: 9/19 15:53

53 Cavalier

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#19

Home away from home

Tell me if I have this correct in my head.

When accelerating, depending on how far the accelerator pedal is depressed, the throttle valve overrides the governor and prevents the direct drive from engaging. Currently on my car the direct drive engages around 20 mph when light on the pedal, and around 40 mph when heavier on the pedal. This seems to funcion fine, and my direct drive engages quite smoothly.

But what is not happening, for myself or Ronald, is the throttle valve overriding the governor to disengage the direct drive after it has engaged. It would seem that it is only the governor that is disengaging the direct drive once the car slows to around 11 mph.

I understand that at higher speeds the throttle valve will not override the governor. But for example, if the direct drive engages at 20 mph, and then you step on it when going 25 mph, the throttle valve should override the governor and disengage the direct drive. Correct?

My question is if the throttle valve is adjusted correctly and is working to keep the direct drive from engaging, what is happening that the throttle valve isn't working to disengage the direct drive?

Click to see original Image in a new window

Posted on: 9/19 16:45

humanpotatohybrid

Re: Direct Drive Clutch not opening on Throttle Input ('54 non-gear-start type)

#20

Home away from home

When accelerating, depending on how far the accelerator pedal is depressed, the force from the throttle valve pressure on the left side of the direct shift valve exceeds ~~overrides~~ the force from the governor pressure on the right side of the valve and prevents the direct drive from engaging. Currently on my car the direct drive engages around 20 mph when light on the pedal, and around 40 mph when heavier on the pedal. This seems to funcion fine, and my direct drive engages quite smoothly.

But what is not happening, for myself or Ronald, is the throttle valve overriding the governor to disengage the direct drive after it has engaged. ~~It would seem that it is only the governor that is disengaging the direct drive once the car slows to around 11 mph.~~ Indirectly, yes. At 11-15 MPH or so, the governor pressure is vented, and the calculation changes thus.

I understand that at higher speeds the throttle valve will not override the governor. But for example, if the direct drive engages at 20 mph, and then you step on it when going 25 mph, the throttle valve should override the governor and disengage the direct drive. Correct?

The force from the throttle valve pressure on the left side of the valve opposes both the governor pressure and the modulated pressure, which both work to push the valve to the right. So if by "step on it" you mean floor it, then yes. Otherwise, no.

My question is if the throttle valve is adjusted correctly and is working to keep the direct drive from engaging, what is happening that the throttle valve isn't working to disengage the direct drive?

Because the valve is designed to have hysteresis, so that when the direct drive clutch is engaged, the forces acting on the valve body are different than when it is disengaged, as detailed earlier.

----------------------------------------------------------------------------------------------------------------------------------------------------------

I made a chart to help illustrate this. X is throttle pressure and Y is governor pressure. Direct drive engages when you move above the red line. It disengages when you move below the orange line. The blue dashed lines are the limits of throttle pressure. The purple dashed lines are the limits of governor pressure. The green dotted line indicates full throttle (beyond which is kickdown). The second graph below indicates accelerator position relative to throttle pressure; note the immediate jump into the kickdown region. Approximate speed values are given for the governor pressures on the left. The numbers on this chart are pulled directly from my calculations in my previous post.

Let's say you are starting off from a stop with half throttle. This is shown in the pale pink line. Throttle position steady at 40 PSI as governor pressure climbs. Once you get to 40 PSI governor, you enter direct drive. In this example we keep speeding up to 56 PSI governor then let off the gas a sec. We floor it (medium pink) and nothing happens. We coast a bit (magenta) then floor it again (purple). This time, we are going slow enough to kick down. Again we let off the gas (royal blue) and coast down to about 15 MPH. But again, we find that we need to hit kickdown to get out of direct (medium blue). We can also see that if we slow down any more, the governor pressure drops out, so any throttle pressure will be below the orange line, and disengagement is guaranteed (not shown by arrow).

P.S. The second graph is just a clean version of the first graph.

P.P.S. If it's not already clear, that kickdown explanation is just saying that one you press farther than full throttle, it just maxes out the throttle pressure. (= pump pressure)

Attach file: