1959 Buick Dynaflow gearbox slips through

[Buickjoe1959]

Hello to all forum members
My name is Josef and I live in Munich Germany.
I have had my 1959 Buick for 30 years now, restored it completely and have enjoyed the car for 30 years.
Now I need some help from you specialists.
Unfortunately I have problems with my Dynaflow transmission.
The gearbox was overhauled some time ago.
The problem is that when I start the car and want to drive away, the Buick barely moves. In low position (1st gear) the Buick moves a little more, in D position I can hardly get away. It feels like the transmission is slipping. If I let the car run for a while and shift through the gears it gets better, as soon as I drive a few meters the transmission works again.
What could be the cause of this?

Thank you very much in advance

Joe

 

[bittmann]

Possibly...your torque converter is emptying ("draining back") when the car sits for a time.

Maybe it's underfilled? I doubt that's the case, but should be checked.

When the car does move, after running for a time, what is the level of your transmission fluid? Does it show at least close to the lower mark on the dipstick? When hot (after driving for a long time), it should be within the indicated range.

This could be a mechanical issue...leaking front pump, etc. But possibly not. Easiest should be checked first!

The 1959 shop manual has a section on troubleshooting the automatic transmission. See page 5-29 for example. If you can get test pressures (front and rear) both when the car does not move, and when it begins to behave, that could point you in the right direction.

The homepage of this site also links to some more in-depth manuals. See Dynaflow and Powerglide manual and Dr. Dynaflow. Much more information there. Could zero in on the cause before ever opening the transmission.

 

[Buickjoe1959]

Possibly...your torque converter is emptying ("draining back") when the car sits for a time.

Maybe it's underfilled? I doubt that's the case, but should be checked.

When the car does move, after running for a time, what is the level of your transmission fluid? Does it show at least close to the lower mark on the dipstick? When hot (after driving for a long time), it should be within the indicated range.

This could be a mechanical issue...leaking front pump, etc. But possibly not. Easiest should be checked first!

The 1959 shop manual has a section on troubleshooting the automatic transmission. See page 5-29 for example. If you can get test pressures (front and rear) both when the car does not move, and when it begins to behave, that could point you in the right direction.

The homepage of this site also links to some more in-depth manuals. See Dynaflow and Powerglide manual and Dr. Dynaflow. Much more information there. Could zero in on the cause before ever opening the transmission.

Hello Bittman

The gearbox oil quantity is correct, I have measured this several times.
I will first measure the pump pressures, I hope this is possible in the installed state, at idle speed.
I'll have to build a suitable pressure gauge so that I can connect the gearbox.
I'll let you know when I've measured the pressures.
Many thanks

Joe

 

[GL03]

Buick Joe if you get an oil pressure gauge kit for use in multiple vehicles it will come with an assortment of fittings with various thread pitch. When you say it was rebuilt some time ago, with the miles we put on our cars, I'm guessing you don't have much mileage since that rebuild. Anyways, can you change the transmission fluid to a different viscosity? You didn't state if it was freezing cold or triple digit hot weather when you are having this problem. After I rebuilt my transmission, I put in Type F fluid instead of Dextron Mercon(Used this before the rebuild with no noise issues). Post rebuild some time ago (not much mileage driven) of the dual path and it is noisy in cold weather with no slipping or drivability issues. If I start it up in warm weather, it is quiet. My car doesn't get much sun.

 

[Buickjoe1959]

Many thanks to everyone who is helping me with my problem!
I did a first pressure test on the front pump today. Unfortunately, the test showed a very low pump pressure. The test was carried out at operating temperature. I have marked the measured pressures in red.
What could be the cause of the loss of performance of the Front Pump?
What can I do (repair or check) to find the fault?
Thank you very much for your help

Joe

 

[bittmann]

Was this tested after you had driven the car far enough to "work" (not just hot, but "working")? If so...wow, those idle pressures are low.

I'm over my head now. I expected this to be a Dynaflow, albeit one of the fancier ones, and to have the same test ports for front and rear pumps, and an accumulator test port, like mine does. You can compare front and rear pressures to determine if there is a leak in the pickup side, for example, or if it's more likely a seal on the front pump itself. Or compare the accumulator to the front to determine if a gasket is leaking. All of this is from the manuals, I haven't ever had my hands in one of these, so I'm learning right along with you.

So, from my perspective, unless you have the tools and expertise, sounds like a trip to the transmission shop may be in order. It COULD be as straightforward as the front pump seal letting go! With pressures like you're getting, it sure looks like something "mechanical" is wrong (low pressure until you start spinning it quickly). And I readily admit that locating what that is will take more knowledge than I have.

But if you can get pressures from the other test ports, MAYBE it'll point you at which subsystem is having the difficulty. At least, that'll let the transmission shop guy have a fighting chance.

 

[Buickjoe1959]

Hello
Thanks for the answer!
I did the pressure test on the lift, the wheels were free and the transmission oil was warm. I just have the problem that I have no real propulsion for the first few minutes after starting the engine. Only when I give more revs does the vehicle move a little....
I will now gradually measure and document the other pressures. Unfortunately, I am not yet familiar with the Dynaflow transmission's technology and mode of operation, and I have not yet repaired an automatic transmission. The pressure connections are all the same in terms of the threads. When I have measured the pressures, I will post them here again. Unfortunately, I have no idea which pressure connections I should compare in order to narrow down the fault. Perhaps you could give me some help here.

Thanks a lot !!
Joe

 

[bittmann]

The 2 Dynaflow Transmission documents linked above - Dynaflow and Powerglide manual and Dr. Dynaflow - have sections on doing just that.

Through inspection, you MAY be able to tell if you have a pickup-tube problem, or a valve or gasket problem, or a seal problem, before ever opening the transmission.

I think your Dynaflow is more complex than mine - but (except for the switch-pitch impeller), the actual routing of power through the transmission should be similar, so maybe the same troubleshooting steps would apply.

It *might* be as simple as "the seal is out of the front pump, the torque converter loses prime, it takes a while to pump everything back" Right out of the 1959 shop manual, it suggests looking at the front pump:



But...that is only one of a bunch of possibilities.

 

[dmva.parts]

What transmission fluid have you been using in your Dynaflow? If you have used the newer Dexron (synthetic), you have destroyed your seals. Dexron III ONLY should be used in a Dynaflow. Problem is that most of the existing seals available for use from anybody are not compatible with the newer synthetic Dexron, and the synthetic causes the seals to swell, then fail.

 

[GL03]

Hello
Thanks for the answer!
I did the pressure test on the lift, the wheels were free and the transmission oil was warm. I just have the problem that I have no real propulsion for the first few minutes after starting the engine. Only when I give more revs does the vehicle move a little....
I will now gradually measure and document the other pressures. Unfortunately, I am not yet familiar with the Dynaflow transmission's technology and mode of operation, and I have not yet repaired an automatic transmission. The pressure connections are all the same in terms of the threads. When I have measured the pressures, I will post them here again. Unfortunately, I have no idea which pressure connections I should compare in order to narrow down the fault. Perhaps you could give me some help here.

Thanks a lot !!
Joe

Did you get a chance to look at the manual for your car?
The dual path transmission in 63 has an in-depth rebuilding guide step after step. I know I will surprise someone with this comment->Dynaflow transmission seems to look easier than the Dualpath.
I disagree about trusting a transmission shop with your car specially when some people get transmission back in boxes and sent out the door. The second most common, they push the customer to retrofitting another transmission.

Anyways if you take pictures at every step of tear down you can retrace back to assemble properly. Tools needed for rebuild are easily attainable. Attaching images of pump from dualpath rebuild. The gray substance I believe is from babbitted bearing material which was worn and cracked which rode on the main shaft. There were leaks and running dry was common. There is a list of parts and services in the DIY restoration section you can find helpful resources.