The Stovebolt Site Forums The Shop Area Engine Shop Hydromatic transmittion or something else? Help

Hi
Awsome Stovebolt webb, you have been great help now for another problem.
1953 GMC 270 with hyromatic. Recently converted to 12 volt. unit runs great, tranny is full of fluid and will move back in reverse but no go forward. I cannot even push unit with engine off and in neutral, in drive,no matter where i put shift lever the truck will not move, it acts like the brakes are on. I did roll forward when I loaded this truck and when I pushed it into my garage and now with full transmittion fluid it won't move. What should I do? thanks in advance good or bad news. Kip

Are there "Hydra-Matic" emblems on the two sides of the hood?
Do you have 1/2 ton truck?
Is it a short-bed or a long-bed (do you know the model number - it is on the ID plate between driver's side door hinges).

If you have an original 1953 GMC Hydra-Matic, I am pretty certain that the ignition must be on in order to "free" the transmission in neutral. There is no Park on that transmission and it locks up in neutral when the key/ignition is off.

Regarding trouble-shooting that transmission, hope that someone who has first-hand knowledge will post advice.

Your transmission is very similar to the one used in Chevrolet trucks in 1954.

Guess again! With the engine not running, key on or off, reverse is the park position on a Dual Range Hydra-Matic. It sounds like the parking pawl has gotten stuck in the output shaft, and won't release. If you can get the engine running and select reverse, the hydraulic pressure should release the parking pawl. If not, you'll need to find someone who is familiar with that transmission to drop the pan and free up the parking system. When the engine is running, line pressure keeps the parking system from engaging when Reverse is selected.
Jerry

Hi Hotrod Lincoln
That was one of my dads favorite songs.
With the information you gave me I jacked up the rear axle and started engine and did reverse with no luck so I put in neutral with engine running and was able to hand turn one wheel while opposite turned different direction, I did this from both sides several times then took blocks out and put in reverse and the truck went back and then in drive and all of a sudden it hit and went forward, I tried this again in reverse and OK then forward a little jerky but worked will re-check fluid levels and try again tomorrow.

This is 5 window, short box and no telling how long this truck sat. I bought it in January as a basket case and it had not ran in a long time.

Again thanks for taking the time to answer my questions, great help. God bless you and yours
Kip in Idaho

Yep, my guess was a little off. You need the the transmission in the neutral position to start the engine. Park is achieved as described by Hotrod Lincoln.

http://1954advance-design.com/Documents/EngineeringFeatures/slides/orig_Page65.html

thank you for suggestions. my truck is 53 gmc short bed five window 1/2 ton.

After reading the posts I jacked my truck up and got rear wheels off ground, started engine put in reverse and nothing seemed to happen then I put in drive and again notheing when in neutral one wheel would spin but the other would not so as it was idol I stopped the spinning wheel and hand turned the wheel in opposite direction and the other wheel turned in different directions I did this from bothsides and then lowered truck back to ground. put it in reverse and it went back then drive and it caught and went forward, no telling how many years this old truck sat before I brought it home in january as a basket case, with the success I will recheck fluids and the go from there again thanks for jumping in now I have hope
God Bless you and family
Kip n Idaho

Kip,
Here is some more light reading on the 1954 truck Hydra-matic transmission

There are only minor differences between the 53 and 54 (and between 54 GMC and Chevrolet) Hydra-Matic set-ups.

When you get to the point of being concerned about the 1st to 2nd shift point (mph), be forewarned that this adjustment is really sensitive. Of course, at this time, this is the least of your concerns regarding this transmission.

Good luck.

thank you, I did take gmc for a test run a few blocks then home, I think another trip over to my neighborts ranch would be good as it is 3 miles. I will watch for shifting and see how she go's. thanks again
Kip

Hi guy's
The Transmittion seems to be shifting good, but is leaking fluid out the bottom from where you can see ?bell housing? thing that spins. Is this opening lacking a cover? it is about 2x2 inches? I will be looking for bolt holes in case there needs to be a plate. if this is normal opening what is my transmittion issue? A seal of sorts and Will I need it rebuilt?

thanks in advance Kip

Hy kip9jeanne, on a Hydramatic transmission the flywheel forms part of the "fluid coupling", there are a lot of bolts around the outer diameter of the flywheel, some of them may be loose, check them for tightness. There is also a seal similar to the type a torque converter equipped transmission uses which may be leaking, have a look and see if you can see where the leak is coming from, good luck.

Leak seems to be coming out of area of the torque converter and flywheel.

The bolts I need to check for tightness are these on the flywheel itself or the case?

thanks Kip

The "flywheel" bolts together, with at least 20 bolts around the perimeter, IIRC. Some of the units have a square inspection cover at the top of the bellhousing, only visible if you remove the middle of the floorboard. The proper name for it is "fluid coupling" as it does not contain a stator to multiply torque. It does have the advantage of getting an almost 100% RPM lockup, not the built-in 10% slip of a torque converter. There's a big O ring around the outer edge where the coupling bolts together, and a hub seal like a more moderm torque converter has. It can leak at either, or both places.
Jerry

more like 30 bolts. you will more than likely have to drop the trans to cure the leak. there is no other way. either the frt pump seal(convertor hub) is gone or the large o'ring is toast. if you are going to do that , you may as well reseal the rest of the trans
ron

Thanks guys, if what I do won't work then I will seek to find a Transmittion mechanic that can re-seal or rebuild. really appreciate your help
Kip