Strange behavior 1959 Hydramatic

[Roger Zimmermann]

A friend of mine has a problem with a '59 Hydramatic. Somebody else repaired the transmission; according to the owner the car performed correctly for 60 miles. Then the trouble began.
The car start in first, go to second, then 3 and fourth for a short time. Then it come back to 3, go to fourth again. At 55 mph, the transmission is going to neutral. By stopping the car, the process can be repeated.
Many possible causes were put in the air, the front unit coupling first. According to the air pressure test done with the oil pump cover, the cover is coming out already with a low air pressure. The car was tested with the selector in low (second gear) and there is no problem, excluding a malfunction of the front unit coupling.
Then the valve body was incriminated; it was removed, cleaned and reinstalled at least twice. Another valve body was installed, same behavior.
The number of discs in the rear clutch is correct, 7 friction and 7 steel.
I still see a possibility: one or both sprag clutch is slipping when enough power is needed. But how to test them?

Unfortunately, I cannot assist my friend physicaly because he is in France. It's not his first Hydramatic, but this one is a nightmare.
Who has THE idea?

[J. Gomez]

Roger,

Interesting symptoms on your friend tranny..! 

You mention in Low (first and second ) there is no problem, how about DR 3 which goes first, second and third? Is there an abnormal behavior on this range?

You also mention there is low pressure, this could be the culprit.

In 3rd speed;

The front unit is in reduction, the sprag clutch is on, and fluid clutch is empty.
The back unit is in direct drive, the sprag clutch is off, neutral clutch is on, and rear clutch is on.

In 4th speed;
The front unit is in direct drive, the sprag clutch is off, and fluid clutch is full.
The back unit is in direct drive, the sprag clutch is off, neutral clutch is on, and rear clutch is on.

So the difference between 3rd and 4th are on the front unit changes. If DR3 is normal trouble could well be in the front unit sprag clutch as you mention or low pressure to fill the front unit coupling.

Just a hit..!

Good luck..!

Jose

[Roger Zimmermann]

Thank you Jose for the time to try to solve that problem.
The low pressure I wrote about was indeed low AIR pressure to test the front unit coupling.
If I'm thinking at all we exchanged as e-mail, my friend wrote that in one cicumstance he had TOO MUCH oil pressure, compared to the data in the shop manual. Could be a wrong spring somewhere; it always hard to tell what's right and what's wrong when somebody else put the hands in a device which is malfunctioning after the work...
I overhauled myself about 15 to 20 such transmissions (5 in one single year!) and I don't understand the problem.
I will have to ask what was the behaviour in D3; I don't remember if he did the test.
I experienced once a malfunctionning transmission I overhauled: when warm, there was no second nor 4th speed. The culprit was indeed a conical cover from the front unit coupling. When the oil was cold, the gaps were not sufficient to let escape all the oil, but, when warm the oil said good bye.
In this case, the transmission got back into third, but not freeweeling!

[Roger Zimmermann]

The last few days, I asked what was the behavior when the lever was in D3: no problem with the transmission.
My friend is in discussion with Fatsco, they told him he should look at the governor. According to a picture from the MPB, there is a washer in the governor; the one from that transmission has no washer. As the transmission is going to neutral at more or less always at the same speed (55 MPH) I assumed that this washer may have an influence.
However, my friend pretends that he overhauled recently a '63 Hydramatic, there is no washer in the governor and the tranmissions is working as intended.
A detail may be important: the governor for 1959 is a stand alone element; from 1960 to 64 there is another part number and a different price.
Any idea?

[J. Gomez]

Roger,

Are you referring to the stop washer inside the governor for the G2 valve circle in red, governor picture attached?

If that is the one, I would say it is needed since G2 valve opens with higher speeds to extend the flow for the 3-4 governor/shift and regulator valves, 3-4 upshift picture attached.

I hope I can get both pictures on this message; else I’ll attach the second one separately.

Good luck..!   

[Roger Zimmermann]

This is exactly what is missing in that governor. I will send your message to my friend. Thank you for your search!