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.