Question about variable pitch stator operation, '55 Buick

I have a '55 Buick, original dynaflow. It is a used transmission that I installed without rebuilding. I have noticed that it drives and operates perfectly except one thing. When I accelerate full throttle from low speeds, it immediately switches stator angle and increases rpm for a few seconds then goes back to cruise angle. I checked linkage from carb to kickdown on firewall and think it is full stroking. All mounts and thrust pads are good. I expected it to hold in performance mode as long as the throttle was wide open but it doesn't.

Tell me how yours is working. Will it stay switched as long as you are at full throttle?

 

It's been a while since I last owned one, see if I remember this straight; It might be a bit sticky, it should hold high pitch a little longer than that if floored. But once the outer elements of the converter get close to the same speed as the inner, the stator backs over to coarse pitch and the car then utilizes its huge torque to get the thing accelerating. RPM rarely goes over 2700 until about 80-90 mph and then starts climbing as the car comes out of its torque band.

 

Check the pressures as outlined in the service manual.

 

Tell me how yours is working. Will it stay switched as long as you are at full throttle? I need to know what is normal operation.

 

On one of mine if the fluid is very hot and fluid is thinned out it is slow to go into switch (from a stop it will not come on until 20 mph) . Other times if activated at 30 mph, it drops out at 45 mph. Pump pressure is low. Another symptom of low pressure is band chattering if hard acceleration from idle in Low.
I have been managing for the past 6 years with STP added to the fluid.

 

OK, thanks for that Willie. I have an engine vibration that I am chasing and Park pawl would not hold on a grade, decided to pull trans and do some checking. After pulling the trans pan, I found more sludge in the pan than I expected and got concerned about the frictions. I have torn it apart only to find that the clutches and bands are reusable, still showing grooves in friction face and clutches measured as equal to or thicker than replacement discs.It looks as if someone did a friction replacement quickie in the past. All it needs is some bushings and a thrust washer or two. I went ahead with total disassembly and replaced clutch and servo piston seals, etc. The park pawl cam locking mechanism shows some wear so replacing it with spare. When I finish, I will no longer wonder how long it is going to last. Amazed at how much sludge and build up was in pan TWICE for internals to look so good. I am looking into installing an inline spin-on filter suitable for long filter life. I just won't install a plastic short life filter that is subject to rupture and leak and needs frequent replacement.

As for the vibration, I have not found problem. Tried balancing flexplate 360*, all I could do was make it worse, not better.

 

When I had a vibration on mine, I later found an 'extra' stator roller loose in the torque converter. I was about to take the torque converter assembled shell to be balanced at a driveline shop that said they could do it. If you did not check pump pressures or are unsure, install the pump from the 56 you pulled out.

 

I checked vibration as soon as I removed trans and converter, still there. Tried balancing flexplate, no luck. I think it is internal but don't understand why I cannot improve by adding weight, only make it worse.

I have the TC and trans apart, no problems. Both pumps are good. Stator piston seal and operation are good. Hi accum is good. Waiting on parts to put back together.

 

And it was balanced with the 56 tranny?

 

Not sure, I never got to drive it much because of slipping in Drive. Don't know if I never paid attention or what, I just hadn't noticed vibration before but vibration is same with or without TC bolted up. Critical is around 1500 rpm and still buzzing up to 2000.

 

That is how mine works (before and after rebuild)
The stators change back to normal pitch after a few seconds.

 

Thanks Bulldog, I am disappointed, expected it to hold in performance mode. I see no reason it should not as long as the hi accumulator is switched. The manual has a paragraph that would seem to indicate it would stay in performance mode as long as the throttle was on the rug. The stator piston is pressure controlled by the hi accumulator.

 

My other 2 dynaflows with good pump pressures work that way.
Remember that the 55 engines are externally balanced front and rear and the 264 and 322 are balanced differently...the front pulley and flywheel/flexplate are different. Is there a possibility that someone substituted parts in the last 62 years?
At 1500-2000 rpm there is some vibration in my originals (not objectionable) ... the rebuilt and balanced one is smooth through all rpm ranges.

 

SUCCESS!
Installed the transmission yesterday, test drove today. Parking pawl now holds even in a bind. Stator now holds in performance mode as long as I hold it to the rug. Haven't tried it at 70 mph yet, it is already twisting nearly 3000 by then. It really adds to the acceleration performance of the 264 from 20 mph up in Drive. Wish I had a 4bbl 322, it would be respectable.
Building a dynaflow is not that difficult with few specialty tools. The worst part of the rebuild is building suitable bushing drivers. The hardest to remove is the reverse planetary bushing which supports the rear of the input shaft. You really need a correctly sized tap and tool setup to pull it. The torque converter requires specialty tools to correctly setup all the clearances. It would be difficult to build a tool kit for that without the specs on the tools themselves. If you have no obvious contact of rotating members, you may get by with measuring all the thrust washers and comparing to new specs, that will get you close.
I went the extra mile and dial indicated the flexplate and TC shell runout at the pump drive hub. Both were out of spec. After many tweaks, I finally got the flexplate runout in specs. Rechecked the TC hub runout and it came into specs. I then mounted the bell housing to the block and checked pump pilot bore runout and face runout. Both were in the neg at top and way out of specs at .010" and .006", maximum allowed is .004" and .005" respectively. Thought it odd that both numbers were neg at top. Installed and checked my spare bell housing and got almost identical numbers. Cemented 2 .010" paper shims at top of block off center of vertical line. Rechecked runout and it practically zeroed out both numbers well within specs. That is amazing and shows how close manufacturing tolerances were, hsgs were within .001" runout of each other. One explanation is that my block may have been surfaced on the bell housing face and was not square. The other is that there was a production problem but I think that unlikely. Checking runout is rarely done but I am glad that I took the time to do it. It may have extended the life of my rebuild.
So far it is leak free, need some more highway time now. Texas John

 

Yes John, the most satisfying thing is that you have done it yourself. The MOST IMPORTANT thing about the "Flow" is the torque converter because the ONLY thing driving the rear wheels is FLUID ONLY. To make the converter even more efficient you could have substituted Torrington needle bearings for some of those thrust washers.
GOOD JOB!!!!


Tom T.

 

Been following this thread with interest.
My hat's off to you; you've tackled a transmission, something I wouldn't have had the cojones to try.
Good Work! You should be proud of yourself!

 

Good job for a great outcome! A 4 barrel will wake up that 264, and don't worry about rpm...the 264 likes and tolerates high rpm better than the other nails.

 

Funny you should mention that about hi rpm. When I pulled the trans, I wanted to check the vibration issue so I cranked it up without torque converter. I was sitting in the seat looking at the tach when it fired up. The throttle hung at wide open and it hit 5500 + in 2 heartbeats before it floated out. It happened before I had the presence of mind to reach the switch and shut it off! Dang it! The 264 accelerates unbelievably fast without the TC bolted up, kinda like a lawnmower without the blade. The linkage to the hi accumulator had hung up the throttle. I cranked it back up and it ran like hammered - - - -! I knew what I had to do eventually, check the pushrods.
I went ahead with trans rebuild and installation. Cranked it up and ran 20 minutes to check trans operation, engine still rattling but improving. Pulled covers and rockers, checked all pushrods. None were what I would call "bent" but some were tweaked. Hammered them out and cranked it up, another 20 minutes and only one was ticking. Next morning I cranked it up and it hushed up. Took car to my 1st car show that day (saturday). I only entered to support the hobby, but I won a very appropriate door prize, WD40 and a can of hand cleaner for my "Work in Progress".

 

Willie, I have a 4 bbl intake off my 322 Century but no carb. I told my son I would probably never use it so he sold it on Ebay. Now I wish I had kept it.