The Stovebolt Site Forums The Shop Area Driveline Hydra-Matic in my *new* 1954 GMC - lots of question

Hey guys, I just came across an extremely clean ‘54 GMC pickup with Hydra-Matic transmission. It's been parked for approx 15 years. My hope is to make it run. I've seen one but never had one -- so lots of questions.

1) There is no “Park” on shifter. How do I park truck and is there a neutral safety switch that needs to triggered in order to start??

Thanks

Hey congrats, that is the same year set up that I have. Park is actually Reverse when the motor is not running, and there should be a neutral safety switch for the starter to prevent it from cranking unless it is in neutral. My safety switch did not work so it would crank and start in gear so they are not full proof. Just make sure you are in neutral before starting. Can you share some pictures?

oldblue48, Congrats on your new to you truck! For more information on operating your truck with the Hydra-Matic transmission see Pages 16 - 20 of the 1954 Truck Owners Manual. The link starts you off on Page 16. Just click the "NEXT PAGE" link at the bottom of the page to continue reading on your topic.

Yes, there is a "park", but it's hidden. With the engine stopped, put the shifter in Reverse. The driveshaft locks up. Yes, there should be a neutral safety switch, probably somewhere on the steering column. The first Hydramatic to have a Park position on the shift quadrant was the "Controlled Coupling" model that came out in 1956, but it was only used in cars, not Chevy or GMC trucks. Have fun with that one.

BTW, the throttle pressure adjustment (linkage from the carburetor to the transmission) is VERY sensitive. A tiny change in the linkage length makes a huge difference in the shift strategy of the transmission. It's normal to get a 1-2 shift at very low speed- - - -5-10 MPH is about average. The 2-3 shift is the one that the throttle linkage adjustment has the most noticeable effect on. There should also be a 4-3 kickdown shift at full throttle.
Jerry

Since your post continues to get more replies on the original "transmission" subject, I've moved the conversation over to the Driveline Forum for further conversation and information.

Is that “controlled coupling” tranny similar to those BOP Fluid Drive units? Where direct drive is all fluid and no gear?

OldBlue:

I think the best HydraMatic manual to start with is the "On The Car Adjustment Service Manual for 1946-55". It has about 10 pages of theory and then describes adjustments you can make without removing the tranny.

I have that book, a 1954 GMC Hydra-Matic Operation and Maintenance Manual and two other HM leaflets in .pdf and .jpg form that I can send you via email. Drop your email address into a PM to me and I'll get the manuals to you.