Packard Forum Index » V-8 (1955-56)

Hi,

I have been working on a 1955 packard 400, 352 V8. It had the cast iron twin ultramatic in it which failed therefore I sourced a 56 model year ultramatic with the aluminum case. It was what I could find and I figured they would have worked out more of the kinks with the newer material casing and internals. This was supposedly pulled from a working unit. I have installed it in the car and changed the driveshaft flange, it bolted up beautifully. The problem is I have no low range. It will drive in high, and it will go into direct drive lockup, and it will cruise like that no problem. However whether or not it is in D-low or low range it does not pull. It will spin the tire in low on jack stands, but it has no pulling power on the ground in the low range.

I have read that there is a throttle linkage adjustment for the center hole on the carburetor shaft, and I have done that, and I have checked the throttle arm on the rear of the transmission with a flatedge. I have also re-adjusted the low range brake band twice to no avail.

I have also noticed that in low the fluid tends to foam. I am using type F and Lucas transmission additive. I do have a case of B&M Trick Shift fluid I can drain and refill with but I am hesitant to do so because I do not think the fluid type is the issue.

I have had the case open on the 56 aluminum transmission because that pot metal screw did strip out, and I did fix it with a new manual lever arm and an aluminum bolt machined into place. That should not be the issue as the gear selector works in all of the positions with audible clicks. There did not seem to be any gunk or debris from what I could tell, it was relatively clean and maintained. I'm at a loss as to what to check next other than dropping the pan and valve body and checking the brake piston and the band tabs. Being that this is a 56 model transmission it should not suffer from that brake piston issue where it drops too far, but I may pull it out and check it.

My thoughts are with the foaming and the lack of pull, it seems to behave like it has low fluid in it, but the levels are fine, but the foaming may be preventing it from building adequate pressure, or something is wrong internally that is causing it to foam, but im not educated enough in transmission internals even with the shop manuals to know how to chase this type of gremlin.

I'm hoping that I'm not looking at a rebuild for something I just installed. It took me all day in the parking lot at my work where it lives. And it seems to be that there is no transmission shop around here knowledgeable in odd 1950s units, or brave enough to take this particular transmission on, so even if it were a rebuild I'd have to do it myself.

This is the only issue I'm having. Everything else is fine, I even rebuilt the little things like the Trico washer pump the Wonderbar radio and they work.

Any help or insight would be much appreciated.

Nice detailed write up. So obviously the low range band is not engaging. Since it drives normal in High the control logic is probably fine. And there's no real way you can be in Neutral when you should be in Low and the rest of the transmission works, so I think your throttle pressure and your selector adjustments are satisfactory, at least for the time being. By the way, it will spin the tires in Low because of the natural drag in the high range clutch pack when it's disengaged. Normal on all automatic transmissions. But that tells me that your band is not engaging AT ALL. Not, for example, that it's too worn.

Unfortunately there is not easy or obvious reason that this is occurring. The short list is that the band tab is out of position or the actuator pin is f***ed up. I think it will be best if you drain then drop the pan. Grab a 1/2 in. drive socket and remove the reverse servo (4 bolts). Slide it so the tubes come out. Then remove the (I think) six valve body bolts. Do NOT switch to a different socket. Then slide the valve body away from the low range tubes. Remove the bendy tube (just twist/pull by hand) then remove the 3 bolts to drop the low range servo.

Send a picture of the band tabs and inspect that they are seated in their actuators (the 90 degree angle pieces of cast metal on pin hinges). You should be able to engage the band by pressing the actuator once the tab is seated. Compare the low range operation to reverse; they are functionally identical. If the low range actuator is stiff then that's your problem.

If those are OK then grab an air gun with a rubber cone tip and shoot like 100 PSI air into the two ports on the low range servo. One will do nothing but the other will actuate the servo. If not, then your problem is somehow in there.

Or you could even be missing a jumper tube into the low range servo for some reason. Let us know what you find.


By the way I'm in Pittsburgh if you would like to send it up.

If the cover of the low range servo is distorted the piston inside will retract to a position where the inlet port is covered and the the servo will not move. They issued a heavier cover to prevent this from happening.

This is a rare failure and I'd rebuild Ultras for years and years before encountering it. The symptoms were just like yours--everything else worked just dandy, but absolutely no low.

After you replace that cap be sure to readjust the low band.

Ross is right. Though the reason I didn't mention that is that issue was identified and corrected before the 56 units entered production. They are also rare to find even on 55 cars. So while it's possible to have that condition, it would occur only if someone swapped the servo out of a 55 transmission or reassembled it out of a random pile of parts.

I and most parts vendors have spare caps.

The bad design is made from stamped steel; the updated one is machined aluminum in a pleasing frustum shape.

Here is a tutorial video on the replacement and also the one in this video is the new style cap.

You should also inspect at the Low Range Brake Band Lever Shaft. Mine broke at the Brake Band Lever centering grove. This could cause insufficient engagement of Low. While mine was identified before getting the car on the road, I know of a case where the Reverse Lever Shaft broke and Reverse was lost.

I addressed the issue by making a new shaft without the grove and centering the lever with spacers.









Riki also addressed this in his thread "band shafts"
band shafts

Yes that was my suspicion as well, that actuator pin.

You can make a new one by buying a long 3/8" bolt (grade 5) from your local hardware store, then cutting off the head and cutting thr unthreaded part to length with an angle grinder. Also use the angle grinder to cut the notch. Hold it in a vise while doing this. Then just reinstall it though I don't remember if this is possible to install from underneath. You may have to drop the trans and get the bell housing assembly and high range clutch pack out of the way.

Use 3/8" split type washers and bend them flat with pliers, and place one on each side, to help center the actuator.

Thank y'all for your responses.

my next guess was to check the brake piston itself, I'll drop the pan on the 56 transmission tomorrow on my lunch break. I took apart the 55 transmission on the bench a few minutes ago to check out what all would be involved. I found that the 55 transmission actually had the newer piston cap installed already. Also, the band tabs on the 55 still looked good and had good tension when I pressed on the lever arm with my fingers. If all else fails I'm sure I can take this brake piston and/or this band and swap it if the 56's band is absolutely trash.

I "doubt" this may be the issue, but if I somehow discover that the clutches on the low range in the 56 are bad, can I just swap the whole low range assembly from the 55 into the 56?

Again, thank y'all very much, and I'll update you on what I find in the 56 transmission tomorrow.

Well the servo (piston) and band are removed in different stages of disassembly. If the band is bad you will have to drop the trans to replace it. The band has grooves, just check if the material is worn to the depth of the grooves at the ends (by the tabs). This is always (by a small margin) where it wears fastest.

But yes they are interchangeable between 55 and 56. The bands are also the same between low and reverse.

Again if you are not sure just send some good pictures of the situation.

Band removal.

High range clutch / planetary needs to be out.

So I got under the pan today and took everything out, and it looks like all that happened was the adjustment side of the low range band had come out of socket. the low range piston was good and moved under air pressure. I put it back in and re-filled it and it goes through every gear now. I put a video down here to show what I found. I'm so glad it was something simple. Shifts are firm and it goes into gear firm, but smooth.


drive.google.com/file/d/1ZSCX1Im08KGxEcy-B9NsXruHDhjyGJD-/view?usp=sharing


Thank you all for your suggestions, hopefully now I can go for at least one cruise before the cold weather sets in, then I'll put it in my booth and paint it back to factory color.

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