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Dynaflow Rebuild - Finally!


KAD36
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Well, I bit the bullet a few weeks ago after years of procrastinating and uncertainty, and had Joe at Professional Transmission and Converter in Marcy NY rebuild the dynaflow in my 55. Boy am I glad he did. He is experienced with Dynaflows, tore it down, mic'd it out, machined and resurfaced parts as needed, installed new parts (both my purchased NOS stash that I had been acquiring over the years and a stash of parts pulled from low mileage units I disassembled in my travels, as well as some other new parts I didn't know I needed). I went to see the unit when it was disassembled and wow, was it tired.

So that others may learn - here were my symptoms:

1) Loud gear whining noise when fluid warmed up and unit in Drive, under load, from 0 to 10 mph.

2) Black film on dipstick - oil got greyish-black quick (like after 5-8000 miles) when wiped on a white towel

3) Chatter/slip in Low on hard acceleration, fluid warmed up. This was reduced after new thrust mounts and mounting pad and proper control valve adjustment, but would still happen

4) Leak down after fluid warmed up, car turned off for about 10-15 min. Basically, you had to put it in N and rev the engine about 30 sec before it would start to move in D.

5) Where did that broken thrust washer in the bottom of the pan come from anyway? Been wondering since 1989. (see old posts)

6) Feels like the switch pitch works. Sorta. When it was rebuilt 20 years ago, upon disassembly it was observed the stator vanes hit the turbine and were all pointing in different directions. Thats fixed, right? I think so......

7) Harsh shift L-D, D-L. Like, BANG-Jolt shift. Only if you keep accelerating and shifted did it shift smooth. How about, we just never shift lest we break it.

8) Sluggish on a start in D, especially on a hill, but thats a Dynaflow, right? And there is a Low gear....oh wait, see 7) above.

So... what did he find you ask? In no particular order

1) The switch pitch was NOT working. The vanes hit the turbine again, the piston that moves the vanes was cracked with pieces missing, and even if the vanes did work the piston was shattered and the fluid would go right past it, so there would never be any variable pitch action. The pieces of the piston came apart and jammed up the whole stator assembly. I had a whole new variable pitch subassembly in my parts collection, which he tore apart, inspected and rebuilt also to make sure all the vanes were properly swaged to the crank pins so they would not come loose and move in unison.

2) The unit was never re-bushed on the first rebuild - they were all shot, hence the leakdown when the fluid was warm.

3) The Low band adjusting screw was fully bottomed out, the band was worn, the drum horribly scored and discolored. Parts were re-machined smooth or replaced as needed. New bands installed.

4) Of the 5 friction plates, only 2 had any friction material left on them, barely any. The outer edges of all were blue/black as if overheated. All new installed.

5) The wrong gasket was used in the valve assembly, and 2 of the hydraulic circuit ports were covered up. Never did figure out what they did, but it was clear something was getting starved of fluid.

6) Found where the thrust washer was supposed to be - in the turbine assembly! The resulting loss of clearance made the unit chew up aluminum and fill the accumulators and valve body full of metal chips. New stator and turbine assembly installed (I had provided both). All new thrust washers, select fit as necessary to achieve specified tolerances, installed in unit.

7) Sprag - shot. I guess the term is "flipped". In any case, it wasn't holding well if at all. Actually, upon reassembly and the first test drive, Joe said "doesn't feel right". He took the unit back out of the car, tore it down again, and somehow determined that the new sprag he got was defective or not to his liking, ordered another, put it back in, drove it, and stated "now it feels right". A new spring and roller kit was also installed, but I lost track of where that went.

8) Front pump worn as expected. New pump and plate installed.

9) Pin on output shaft that turns the driving gear on the rear pump sheared off. Rear pump never worked. I think thats a don't care unless you are going to push start a Dynaflow car, but in any event, that was fixed.

10) The switch pitch linkage was not properly adjusted at the high accumulator and was not engaging the piston that allows fluid to flow to the stator to switch the pitch, not that it mattered because the stator self destructed anyway.

11) All seals and gaskets replaced, including torque ball seal, unit pressure tested. I haven't seen a leak yet.

It took about 3 weeks for the rebuild, and the price was reflective of what was found and I thought it fair. Joe put alot of pride and attention into the rebuild - the car was not leaving his shop until he knew it was right and I was happy with a complete test drive. I am totally delighted with the work and the operation of the unit and it was worth every penny. The unit is cleaned and painted (I wanted it black). After 500 miles the fluid and stick are perfectly clean as they should be. I find that I am fire-walling the throttle far too often and the car is more of a pleasure to drive than I ever imagined. The acceleration is really smooooth. What is ironic is I probably put 40,000 miles on the car with the transmission in this worn condition - amazing it still worked. Joes opinion is a Dynaflow is a fairly simple and durable unit. I have to admit, if all a unit needed was bands and clutches and seals, and the disassembly stayed at the major subassembly level and there were no other "nuance" failures, my skills would probably be sufficient to disassemble, replace the typical worn parts, and reassemble. If I had tried that with the condition my unit was in, I would have been way over my head and not know what to look for.

Wow....so, hows it drive? Boy, I have no complaints about a Dynaflow now after almost 30 years of what I thought was normal operation. It takes off in Low, like I'm afraid to push it too hard from a standing start. Yes, the tires do squeal in Low now, no using gravel or going around a corner to cheat. I can pull out of anyplace in Drive with confidence and there is hardly any hesitation like before - actually, I would compare it to my Tahoe if you started it out in second gear (some of the GM light trucks allow a 2nd gear start). I never heard nor felt how the variable pitch was SUPPOSED to work - there is about a one second delay, and then it sounds like the engine is going to crawl out from under the hood. It has NEVER done that before in all the years the car has been on the road. The rpms really jump up - it is a very, very noticeable difference in acceleration vs the subtle acceleration of what I thought was a solid working unit before. The shifting is also very smooth, and there is no whine when you pull away from a red light. When we went on the test drive and I had to pull out quick, out of habit I put it in Low. Joe pointed out - you shouldn't have to do that any more. He was right. On the drive back from Utica, I got in the neighborhood of 17 mpg doing a steady 65-70. It does not take much throttle to keep the car going. I historically got about 15-16. Time will tell but I expect an improvement. You could probably put me in one of those dinky 50's commercials as a gleaming new Buick buyer.

Hope the thread is informative and entertaining - now to put more miles on it before the snow comes. Next project - a couple more chrome pieces, bodywork and paint. Oh and now that the dynaflow doesn't leak, it makes my rear main bearing leak look worse, so will be digging up that recent thread on rear main seal fixes using the heater duct wire to address it. I have some pictures of the worn parts and can post when I get them off my phone.

Edited by KAD36 (see edit history)
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It is great to hear about your experience. Even better that you found a very competent rebuilder, one who knew or had enough experience to know what to look for. Even though my own Dynaflow seems to function very well, I could not help thinking how long you reported using this car with this disfunctional unit, and how you came to think it was functioning normally.

And given that Joe worked with you to list all that went wrong, I wonder if it's possible to pick his brain a littlle bit more, to try and get his perception of the percent of times he has come across these particular problems. While purely conjecture, and most likely enhanced with the time warp over his professional career, none-the-less, I would like to get some feeling for if he thought your unit was the exception, rather than the rule.

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Hi John - I can call and ask him and post. He asked me for a follow up call after 1000 miles were on the car. His opinion was the weakest part of the 55 design was the sprag - apparently they beefed it up or improved upon the design in 56, we talked about that. The ears on the early bands occasionally snapped too - he showed me a later one (which I had in my collection that was different than in the car - not sure if mine was a GM or aftermarket) where the ears had more of a boss and re-enforcement on the ends. They are in the car now. His opinion, same as many of ours, is the 56 transmission is desirable from the mid 50's era because of the extra stage in the torque converter - more efficient on start up. The heat exchanger we all know is an easy swap, and the tail-housing & u-joint would have to be swapped to match the splines on the 55 driveshaft. If my savings account was a little deeper, I would have bought a 56 unit and brought it to him and put that in the car. Utica is about 90 min or so from Binghamton - same for you?

Here is the website - he advertises Dynaflow rebuilding right on the front. Shop is clean, neat and well organized also - he gave me the grand tour. There was also a 55 Chevy with fresh paint on it when I swung the Buick in and dropped anchor. The one night I had to stay late at work in Syracuse and he hung around late for an extra hour until I could get there so we could go through all the broken parts together, explain what happened and determine the proper parts to fix. Another thing - he believes you get what you pay for in rebuilding kits, especially with the clutch packs and friction linings. People bring him no-name brands and he will advise against installing them because they usually don't last. I had some of the hard parts for him to use and let him choose his supplier of choice for soft parts and anything I didn't have (most of my stuff was NOS GM, acceptable used, or LEMPCO). This guy is tops. Here is his companies home page - check it out:

Professional Transmission and Converter - Home Page

Heres some pics of the unit just prior to going back together (the first time). I still have to get the busted pics up here. The turbine assy in Picture #2 was where the most damage was - the inner vane area had a big groove cut into it from the contact with the stator vanes and the metal had filled every nook and cranny in the trans.

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Jeese John - just remembered I owe you a video of the vac gauge on my car - sorry about that. I tend to post in surges. Maybe this weekend before the big storm hits.

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Edited by KAD36 (see edit history)
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Thanks for posting this stuff. Those pictures are intriguing. I've never seen the insides of one of these. I'd be especially interested in the pictures showing the damages parts next to the replacement parts.

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Looking at an automatic all apart really makes one wonder HOW they came up with the design. I understand lots of such was the result of lots of testing/experimenting, etc. Still a tad overwhelming.

Around 1953-54 my father's dealership receive from Buick a small hand held salesman's sample of an automatic torque converter. It was clear plastic, see-thru with colored fluid inside. It had a small crank handle, and on the other side of the shaft was a ball that you gripped, so when you turned the crank, you would feel the pull. As I recall the unit was approx. 8" in diameter.

Has or does anyone else remember this piece? Sure would be a neat piece to own today.

Dale in Indy

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Damaged parts

Photo 1 - Contact damage from stator. At the center of the turbine, below the pinon gears, was where the broken thrust washer should have been. the center of the turbine by the pinons had deep wear grooves all through it.

photo 2 - Shattered piston pieces missing. Compare to prior photo of replacement stator on bench pulled from low mileage unit prior to reassembly. There is a sealing ring that goes around this part, and when the piston in the high accumulator is actuated from the throttle linkage and ports fluid here, the pressure on the back side of this assembly is what moves the piston, rotates the crank pins, and hence the stator pitch. You can see one of the stator blades under the pencil misaligned from the others as it was loose on the crank pin - a couple of them were jammed misaligned like this, making for a rather inefficient torque converter. The piston and blades should move freely when assembled in the stator - mine did not. You can see some of the piston debris on the newspaper below.

photo 3 - Disassembled stator with the broken piston - the jagged areas by my thumb should all be round, with a slot to set the piston ring in that seals against the cylinder to actuate the stator.

photo 4 - Picture of a good friction and steel plate, compared side by side to what came out of the car. 3 of the 5 were worn and had no material left on them, all were discolored. This was the "better" of the remaining 2 friction plates that had some material left.

picture 5 - Flip side of stator showing contact and 2 of 4 broken stator vanes.

pictures 6&7 - Scored drum - compare to photo of resurfaced drum on bench prior to reassembly

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Edited by KAD36 (see edit history)
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What an interesting post. I'm currently having the twin turbine Dyanflow rebuilt for the 58 Buick Special by a local shop in the Chicago area. I'm waiting on how the job turns out before mentioning name. What did you spend for the rebuild? Where did you get the parts?

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KEN, beautiful work! How important was your collection of NOS parts to getting the job done? Obviously, it saved you some big money but were there things like the turbine or the switch-the-pitch assembly, which the shop would not have been able to repair or readily source?

We used to have a brilliant auto transmission mechanic here in Edmonton, Eldon Lunger, but he died far too young - late 40's maybe - about twenty years ago. I don't know where I would take my Dynaflow for a serious repair now.

Armed with the excellent advice on these forums, I'll be tackling a major servicing of this beast - seals, gaskets, obvious wear items - sometime in the next year. I'd be very pleased to discover that, with a refreshed Dynaflow, my car isn't such a slug after all.

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Dave - interested to hear how you make out. My NOS parts were purchased at Carlisle, Hershey, eBay, or occasionally I would see something NOS on line at a vendor. I was also lucky enough many years ago to find a wrecked 30,000 mile Roadmaster in a yard, bought the transmission and with the help of the yard man gutted it, and inspected the pieces in an afternoon, cleaned them and took them home. You can get an idea from FATSCO or Autotran of what is still out there based on what they list in stock - assuming they list all of their stock - or watch the CARS or Buick Farm NOS listings. Seals, soft parts, clutches, bands, sprags seem to still be available or findable. Oddball "hard parts" like stators, pinions, the variable pitch turbine assy etc seem to be more difficult to find, however an experienced vintage rebuilder probably has sources not available to us.

I went into the first rebuild pretty clueless back in the 90s, I trusted a shop back then that today am certain did not properly know what he was doing and did not repair everything that was wrong with it. It is disappointing to trust a shop, drop a chunk of change, be told X when Y was done, and have lack of confidence in the result. There is just no way to tell. Why the Low band adjusting screw was bottomed all the way out and the band material gone and drums scored tells me he never replaced that band and never knew how to adjust it. Wrong valve body gaskets covering up 2 ports? Careless. I paid almost 1000 back then. I failed to ask enough questions, didn't understand how the transmission worked, didn't go see the old/new parts, had no referrals, didn't inspect the shop for cleanliness and organization - my lesson learned was these things are a must do when you are getting any unique, non typical significant work done on a vintage vehicle that you don't want to do yourself. Or - find a place that "does it for a living". Often. Don't trust "I used to work on them" as good enough. I should have brought it back to him after the first 100 miles when the oil looked to me like it had metal in it - it wasn't "band material" or "new parts breaking in" - it failed that quick. But my options then were limited and I figured I would drive it till it dropped. Well - it never let me down!

After studying a shop manual, reading many posts and getting sound, proven advice from knowledgeable people on this forum who were willing to teach me, it was beginning to appear things weren't 100% and I made a list of those areas most likely needing attention, assuming metal had been circulating through the unit and it wasn't "band material" after all, and the thrust washer pieces were not carelessly left in the pan, but a new failure after the rebuild. You can make smart purchases on the likely parts needed at a good price when you are on your schedule vs having a car laid up in a shop. Guts from the used unit, for those oddball things like the stator assembly that may never show up again. Since the vanes had been smashed on opening the unit during the first rebuild, my worst case assumption was the first guy didn't know what he was doing and they would smash again. If it was slipping, my hunch was clutches and bands shot and hence any gripping surface probably scored and burned so picked up those parts. Found a new front pump and plate at a swap meet. Reverse ring gear on eBay. New shafts at a old dealership in PA near my grandmothers house. Brand new bands at Carlisle one year - they were unmarked, but I knew they were correct for the car. It was a fun journey.

This time around I wanted a rebuilder who was willing to take the time to mic out and select fit everything and not just slap clutches and bands in during a rainy afternoon. I also wanted someone with ready access to a machine shop in case parts needed to be fabricated or milled. Generally, all the parts suspected bad were indeed bad and I had solid replacements ready for the "unobtainiums". The rear pump inoperative, wrong valve body gaskets, and this spring and roller kit were surprises.

Rob - in my opinion, having those parts is only important if you suspect catastrophic damage. In my case, the metal in the oil and the inability of anyone to remember if the pan was cleaned out the first time were red flags. My advice - if the dipstick wipes dark grey or black on a white paper (even when the oil looks red), if it turns a dark maroon or black well before a scheduled change (20 - 25000) miles, or you have seen any metal pieces, shavings or thick layer of grey metallic muck in the bottom of your oil pan (check with a magnet - although the turbine and bushings are non metallic), you could have some damaged parts in the unit. Call and talk to a rebuilder and see what they think on parts. Otherwise, you should be just fine with whats readily available out there.

Most important advice - trust your instincts.

Some other advice - in the event a shop cannot get a part, will they let you work with them to find it? Ask your rebuilder if it is ok if the car is laid up in his shop for a month or so. Will he keep it inside locked up for you? Does he have enough floor and bench space to accommodate your unit if a long term parts hunt is in order? That was another lesson learned - I ended up paying a daily shop fee the first time because the car was "taking up space" after a "reasonable time"elapsed and other customers could not get their cars in - so he was loosing business on my account. Bonehead.

I took the car for about a 30 mile trip today - its 35 deg out and there is still nothing like getting behind that big old red and chrome wheel, kicking both heaters on until the heat blasts you out of the seat, and motoring down the highway at 70 mph. One nice thing about cold weather driving - no bugs on the chrome!

Edited by KAD36 (see edit history)
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The only thing I would add to Ken's last dissertation is if possible do the pressure checks as outlined in the shop manual. That too will tell you what parts of stock up on and maybe even tell you that the tranny is basically sound and just needs soft parts (seals, gaskets, clutches, bands).

Willie

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The only thing I would add to Ken's last dissertation is if possible do the pressure checks as outlined in the shop manual. That too will tell you what parts of stock up on and maybe even tell you that the tranny is basically sound and just needs soft parts (seals, gaskets, clutches, bands).

Willie

Excellent suggestion Willie, good idea and very preemptive.

Here is a video from mudbones garage showing just that:

Edited by buick man (see edit history)
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  • 1 month later...

KHALIFA, David Edwards runs Auto Tran Autotran5@aol.com, near Boston MA. He has everything you need to repair a Dynaflow. He sells overhaul kits that include all the seals, gaskets, and normal wear-and-tear parts but he also sells individual seals, if you're sure that's all you need.

Last week, I ordered an overhaul set for my '57 from David. I got a notice from USPS the next day, saying that the shipment was on its way.

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KHALIFA, David Edwards runs Auto Tran Autotran5@aol.com, near Boston MA. He has everything you need to repair a Dynaflow. He sells overhaul kits that include all the seals, gaskets, and normal wear-and-tear parts but he also sells individual seals, if you're sure that's all you need.

Last week, I ordered an overhaul set for my '57 from David. I got a notice from USPS the next day, saying that the shipment was on its way.

Thanks Rob,

I will send a message to David and check with him my Dynaflow trans needs.

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