Packard Forum Index » V-8 (1955-56)

What does The rebuilder have to say about the problem?????
Maybe take it back to the rebuilder.

55 mph in recent temperatures is NOT any where near servere service. More like medium service demand at the highest. The rebuilder should be advised of your problem.

Problem is that if u add the extra oil cooler and the probelm persists then u're back to square one.

As i said earlier my 56 Exec runs here in Tennessee in heavy city traffic at summer temps of 90 - 103 degrees F AND open rural Interstate at 70-80 mph sometimes for up to 200 miles ata time and rarely less than 30 miles one way. i have only the factory oil cooler. My trans is original with 52K + miles on it. I've personaly put 18K+ miles of that on the trans myself over the last 10 years.

Throw yours back to the rebuilder for analysis and let us know what he says..

Concur with PackardV8 on this one. The fact that the trans was slipping both in the past and now is apparently heating to the point oil darkened indicates a mechanical problem.

The two most likely:
1) either the linkage and resulting throttle pressure is not accurately sensing the speed load and commanding enough pressure to the system or
2)that pressure or another is being diverted due to a leak around one of the bushings or sealing rings.

The pressure keeping the high range clutches tightly engaged varies and is dependent on load. Too little pressure will allow them to slip with the friction overheating everything. The more heat, thinner the oil, more slippage, more heat until a point is reached where the car sits there unable to move.

The manual has a pressure gauge diagnosis routine but i don't recall all of the details. See the manual. HOWEVER the procedure does require a special adapter/spacer between the pan and the trans. Maybe a spare pan can be modified in liue of the special spacer to allow the gauge to be connected.

I mite add that the pressure test routine would be better done on the road under operating conditions. This would require running the gauges to the inside of the car or possibly mounting to the hood ornament or in place of it so the gauges can be read while under operation of the car.

Have a look at the heat dissipation thread. Owen_Dyneto has brought up a couple of excellent points re the torque converter being a cause of excess heat. If the fluid is dark and smells differently than fresh, would still look to the high range clutches and pressures though.

Haven't checked with him yet, but the email threads on the different things to check will be topics I'll address to see if they were done during the rebuild.

Thanks

Hi,
Does anyone know the approximate operating pressure of the Ultramatic transmission fluid at the cooler. Reason I am asking is I have a used but almost new B&M transmission cooler lying around which after reading this thread I want to fit on my 55 400, unfortunately there are no hoses with it so I need to buy some of the correct rating.
Thanx,
Dave UK.

Have you browsed the pressure charts in the service manual? I looked very briefly and didn't see specific reference to the cooler though you may want to look more carefully for that. The highest pressure I noted was front pump pressure of 170 psi in reverse.

If you are worried about the pressure then use buy the same type of hose they use for fuel injection. It usually has a higher pressure rating then regular heater hose. Any parts store should carry this.

The cooler is in the converter out circuit and the return just empties into the pan. In 1955 converter in pressure listed is 40psi (2.75bar) at approx 20mph and drops significantly when in direct drive.

Assuming the worst conditions with a higher speed, no direct drive, no energy loss in the converter so converter out is same as in, then I would doubt it would exceed 100psi (6.9bar). A normal pressure rated hose should work.

Gates makes hose in 5/16", 3/8", and 1/2" I.D., specifically for transmission cooler lines.

I have had to purchase it for the shop, on ocassion.