3 Speed Hydra-Matic Question-HELP!

Up until the other day, my transmission worked, for the most part, flawlessly. Now, when it is put into gear the engine wants to stall. It won't go into reverse while the engine is running, but will go into reverse with the key and engine off. The fluid is full and bright red.

I have never adjusted the linkage, since it worked, I thought, just fine. The timing is right on the money at 8 Deg.....the distributor has not moved from where I put it when we originally got it running. It was maybe a Qt. low 2 weeks ago and all Chevron had was ATF, or 2005 and prior GM vehicles using Dex-Merc III. The label said MD-3. I have a suspicion this may have something to do with it, simply because this popped up after I put it in.

The transmission has not made any strange noises and always shifted and downshifted just fine, nor does it have any noticable leaks of fluid anywhere. (other than the tiny drip from the rear seal on the yoke) but it is very minimal.

Yes, it has 115,000 miles on it, but really don't know if anything has ever been doneto it. still doesn't explain the sudden malfunction. I know these share almost no mechanical parts or design specifications with any other GM (TH200-TH400), so they are kind of a stand alone mechanical marvel/ masterpiece.

On another note, is it possibelt that it may have too much fluid in it? My 383 Chevy wss overfilled, once by a half quart and it spit out the dipstick and fluid when it reached temperature. This one has NOT done that, yet, anyway!

Does anyone have any suggestions?? I am open to any and all theories...

I have never attempted to rebuild an automatic transmission, but you never know. There is only one shop in town that has someone who even remotely knows how to rebuild one of these dinosaurs, and he's my neighbor, even he's not sure!

Chad.....The manual lists five possible causes of not being able to select reverse gear. I hope it's only the first or second, because the others require opening up the transmission for repairs.

The shift linkage has become misaligned
Something interfering with the linkage
Governor valve sticking
Broken governor rings
Reverse blocker piston sticking

If the fluid that you put in is not compatable, it could cause the sticking. You might first try a complete flush and fluid change. All of the newer fluids are supposed to be compatable with ATF TYPE A, but who knows for sure. It takes between 9 and 11 qts. for a complete drain and refill, but it's worth a try, compared to an overhual.

By the way, the transmission is a 4 speed. Some of the up-shifts are so smooth, that without a tachometer you don't realize you're in a higher gear. Another reason to love these cars......John

John- I did some thinking and talked to my neighbor about an hour ago. He owns a Trans-Medic franchise. He does not know much about these Hydra-Matics or Jet-Away's, but he says overfilling is a good possibilty as to why it is not wanting to shift into reverse while it's running. I am going to drain it and pull the pan tomorrow, hopefully that's all it is. I'm not sur exactly how much it is overfilled, but I guess I'll find out.

I didn't know they were 4 speed's...the indicator has (P N D R L R) so, I just assumed it was a 3 SPD. Hmm... I learned something new! I should have known better than to put the MD-3, in there, since I had never seen it before. Anyway..the fluid is not frothy and it's not leaking out all over the floor, so, hopefully I didn't blow anything out. Thanks for the info, I was hoping you'd respond......Chad



P.S. Thanks for the neat article on the Fairfax facility.

I will be going to Tap Plastics later this week, I have been busy doing Spring projects and cleaning. For some reason, I decided to mow 7 acres with a riding lawnmower and a DR brushcutter, instead of waiting until summer for the Hay guy. All this freakin' rain made the grass/ hay/ weeds were almost 2 feet high! I will NOT be doing that again!

Funny, my acting jobs are getting in the way of my "other" work! Such as life, I suppose...

Good luck on the transmission bluebomber! I know what you mean about finding someone who knows about these transmissions!

Chad.....I've always believed that "work is the curse of the drinking class." Unfortunately, I also subscribe to the idea that the only thing that money can't buy, is poverty.

Fascinating that they were building jet fighters at the same time they were building cars there. Sometime between our cars and 1965 the letter designating the assembly plant change from "K" to "X." Funny, my wife's 2010 Lacrosse was made there......John

I found and fixed the problem! It was the reverse release spring (4.189 in the diagram below). It looks like a wavy washer on the reverse cone. It is not actually split like in the diagram, but is round. When I removed the tail cone and reverse housing spacer, the spring fell out in 4 pieces. Not an easy task with the trans still in the car, but it can be done. Removing 4 snap-rings and heating the bearing to coax it off the shaft, I was able to disassemble the the back half of the transmission fairly easily. Lining up the parts on the bench and cleaning them was the key.

There is a guy here in Portland that has a ton of vintage transmission parts, except these are so uncommon, I got lucky he even had one! In the process, I replaced the bearing as well, since heating them tends to soften the balls and cage housing. Besides, it had 115,000 miles on it. The rest of the internals were in amazing shape for their age.

The governor has 4 oil rings on it, one of which was broken. If anyone has ever tried to remove and replace one of these gems, farting while holding one will break them. Another cool guy, Rod, who rebuilds vintage Hydra-Matics, gave me a governor, rather than attempt to take them off. I am greatful to have such good friends and fellow gearheads, willing to help another man out!

Thanks for all the thoughts and help from you guys here, it's what makes this hobby (addiction) worth the effort! I now have a factory service manual (Thanks Joe D'Orio @ Old Car Parts) that was a tremendous help in this endeavor! He also sold me an NOS trans mount, too! Mine fell into pieces when I took it out.

I would also recommend everyone pull the pan on their cars and check the filter. Although there was no metal or anything other debris in it, it should be done at least every 20,000 miles or if it has sat for any long period of time. The screen is the cleanable type, brass and stainless mesh. There is no replacement available from any auto parts store.





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By the way, the rear bearing is available at just about any auto parts store. I have the number if anyone interested.


I have a new found respect for the Strato-Flite Hydra-Matics produced by GM in the day when things were built to last.

My jetaway hydra is currently hanging from the engine crane - i just painted the pan pontiac blue today - the trans body black, and the alu reversehousing and front is left clean and unpainted. It took days to clean the trans, but it is starting to look decent. I hope it will work as well as when i took it out.
Maybe i should pull the pan and clean the filter - i have been wondering why there was no filters available for pre 60 jetaways, but it is properbly because it is a cleanable filter...
I have been doing some research on these trannys, and they are pretty hard to find any parts for, so i guess i just have to cross my fingers that it is going to last. Interesting that they made a 4 speed with 2 different shifting programs back then, when most of the stuff was 2 speed ultra slip o matics. I also like the way that the first gear stage is before the 'converter', so that the stall speed can be lower, hence the slip minimized.
Even the names are neat : Jetaway, Stratoflight !