The Stovebolt Site Forums The Shop Area Engine Shop Hydromatic trans. rebuild question

I just finished reading "TH-400 rebuild question" so would like to open a new thread.

I hope Hotrod Lincoln will jump in, as well as others, as it sounds like you have experience with this trans.

I have a 54 1/2 ton chevy w/hydromatic. The trans needs rebuilt. First, second, reverse, and park work great. No third and fourth gear. I have removed and cleaned and checked the shift control body. All seemed to be OK. Still no 3rd. and 4th. gear.

The estimates I got about three years ago were 900-1200, with no shortage of shops willing to work on it. The kit costs about $400.00 today. I also have a parts trans - same year and model, that the P.O. said worked fine except for park. He got tired of the leaks at the torus.

Is this a trans that can be rebuilt at home by a good mechanic. The truck is disassembled at this time.

I am going through a similar project right now as I am putting Hydra driveline in my 54. I am looking for a couple of parts. I will pass on the parts info I have gathered if you will e-mail me, Don't want to cross the advertising line in this forum. Thanks G.H.

Is yours the Dual Range model, with two "Drive" positions? If so, it's a very complex transmission, and is extremely unforgiving of mistakes during a rebuild. I have a couple of factory manuals stashed away somewhere, with detailed rebuilding instructions, and my father was one of the first men in Nashville, Tennessee to repair that transmission, back in the late 1940's. Since the last of the dual range transmissions was produced in 1955, finding someone who is really good at rebuilding it might be difficult. It's a lot more complex than the later models like the Turbo 350, for instance! Shop around for a very experienced oldtimer to get your rebuild done!
Jerry

Gonna disagree with HR Lincoln on difficulty. It was the first trans I ever rebuilt and I did ok. I think it is much easier than the TH350 and WAY easier than the 700r4. It is a heavy sucker! I did have to make a few tools to take it apart, not much more than some allthread and plate steel.
Mine was (is) a Dual range Hydramatic, but it is in a 59 caddy. So dual range was available at least until then.
I bought a rebuild kit from a well known company, it was complete with seals, gaskets, hard parts, bushings. Very happy with the quality.

If Lonnie is talking about the original HydraMatic transmission on a 1/2 ton Chevy truck (with enclosed driveshaft), what is meant by a dual-range model?

I recall that the shift indicator has settings of something like "1-2", "1-3", "1-4", and "R".

Thanks,
Tim

Tim you are right in the positions of the shifter. From left to right they are N 1-4 1-3 1-2 R.

I did some research on why they are called dual range.

Prior to 1952, the transmission provides four different control or operating ranges which may be manually selected by the driver through movement of the shift control lever at the steering column.

N - Neutral
Dr - For all normal forward driving
Lo - For maximum power forward, such as operating up steep grades or in sand and also to be used as a brake when desending steep grades.
R - Reverse.

The 1952 hydra-Matic Drive provides two forward driving ranges. (Hence Dual Range)
Dr - 1-4 for normal driving
Lo - 1-3 for driving in congested traffic and hilly or mountainous country.

The previous discriptions are for cars, the following are for trucks.

N - Neutral
1-4 - Normal forward driving
1-3 - For faster acceleration and in congested traffic.
1-2 - For controlled power - pulling through sand or snow, and when necessary to ascend and desend steep grades.
R - Reverse

A note of interest about the 1-2 range. "This position should be used to place vehicle in motion on icy roads as vehicle can be moved in 2nd with light to medium throttle... the second speed start is used on the 1/2 ton only".

The manuals have many more items of interest in them.

Therefore cars before 1952 had a single driving range for forward (1-4), 1952 cars had two driving ranges (1-4 and 1-3), and trucks had three forward driving ranges (1-4, 1-3, and 1-2).

The truck trans. was the same dual range hydra-matic as the cars with different valving to provide for the driving demands of a truck.

Curly I hope you are still reading, where did you get your rebuild kit?

Thanks for the posts.
Lonnie

I have been getting gaskets and seals from this guy. Has been very helpful and has had everything needed so far in the way of seals and gaskets. Hydramatic parts

In 1956, there was a basic change in the design of the Hydra-Matic. The "Controlled Coupling" Hydramatic was also a 4-speed, like the Dual Range, but its internal parts are way different. The trans was sometimes called the "Jetaway", but that one was also a different design. To the best of my somewhat limited memory, the dual range was only produced for 2 or 3 years, 1953 through 1955, I think. I don't think the controlled coupling trans was ever used in the stovebolt trucks. The CC trans was used from 1956 through 63 or 64, I think, in Olds, Pontiac, Cadillac, and a few Buicks one year, when the Dynaflow plant was damaged in a fire.
Jerry

Jerry
The dual-range hydra-matic was used in the Task Force trucks as well. Both GMC and Chevy. I don't know if they were used in all years.

GMC used the trans behind the Pontic V-8 and their six cylinder. Chevy used it behind their V-8, that is where the bell housings came from for all the B&M Hydro cars with Chevy engines. I have never seen a 55.2 with a six and hydro, but that doesn't mean they didn't make it. I don't have the research material to check.

Lonnie

The dual range hydro has a cast iron case, where as the later "hydra-matic" transmissions have an aluminium case. Is that correct Jerry?

Lonnie

You made me look! I went to the 54 truck service manual as wellas the truck service supplement manuals and they both call it Hydra-Matic in 54. I thought the later aluminum trans just lost the dash in it's name. But hey! I am anxious to listen to anything anyone can pass on to me on this trans. A year ago, I didn't really know this trans existed. Now I have one kicking my butt every opportunity I give it! Thanks G.H.

That's right, Lonnie. The Hydramatic (not sure about the dash) originated in 1938, and it had a clutch. By 1940 or so, they had developed a fluid coupling so the engine could idle at a stop. Some WW II tanks used Cadillac engines and Hydramatic transmissions. The Hydramatic was used in non-GM cars like Nash after the war, as well as Olds, Pontiac, and Cadillac cars. Buick had the Dynaflow, and Chevy had the Powerglide, starting in 1951. GMC trucks used the Hydramatic with either a Pontiac V-8, or an inline 6-cylinder during the early 50's. I can remember driving a GMC road tractor, pulling a dozer on a lowboy, in the early 60's with a Hydramatic in it. The most recent overhaul I've done on one of those transmissions was from an early-60's Pontiac Grand Prix with a controlled-coupling Hydro. That's the aluminum-case trans you're thinking about, the 1956 to 63 Controlled Coupling. There are a couple of "O" rings, 1/16" square, and about 9" in diameter on the controlled coupling torus which are the pits to assemble without cutting them! Pontiac and Olds used a "Roto-Hydramatic" in the mid-60's somewhere that was a real POS!
Jerry

I'm ignorant on these hydramatics but have noticed that the GMC boys seem to really like em. If some of these were used on cars--does that mean that some are available for open driveline (hotchkiss) rearends or are they all set up for torque tubes--can they be convered??

Yes, some were set up for open drivelines, but I would think twice before going to a lot of trouble to adapt one to a non-original application. There are much better, newer-design transmissions out there. The Hydramatic has a fluid coupling, not a torque converter, so there's no torque multiplication on breakaway. Just before the vehicle starts to move, a torque converter doubles the starting torque. A coupling simply transmits whatever torque the engine makes, so a lower-geared rear axle is needed for adequate acceleration. The downside of a torque converter is that it loses 10% of the RPM as the power transits the converter. (1,000 RPM in, 900 out). Of course, an overdrive transmission with a lockup torque converter solves both problems! The Hydramatic gets almost 100% RPM efficiency, but doesn't multiply torque, and it's not available with overdrive. It's also over 40 years old, so parts can be a little hard to find.
Jerry

I'm a new guy and this forum is a wealth of knowledge.
I'm looking to replace the original hydra-matic trans in my 54 chevy truck. I've had an outstanding transmission specialist rebuild it and go back into it several times because it slips in 3rd gear. He feels there must be a crack or something in the core loosing hydraulic pressure only in 3rd. His test with air pressure always turnout fine when the trans is on the bench. I don't suppose I'd be lucky enough to fine another original Hydra-matic (first choice), so looking for optional automatic transmission to hook to my perrrrfect 235 straight 6 engine.
thanks,

What I'm asking is what are the other transmissions out there that will bolt to the 235?
I've heard powerglide, and 350 with adapter plate. Which one is recommended?
thanks again

Hy guys, the hydramatic was used in trucks up to 1962 when the engines were changed. Just as a point of clarification, a fluid coupling has a range of R.P.M. in which it is efficient, above and below that sweet spot the drive is either not efficient, or it absorbs horsepower. Hope that helps.

Lonnie,
I would recommend that you contact California Performance Transmissions in Huntington Beach, CA. He is the real Art Carr and has been around since the Hydramatic was new.
Fred

rfs56trk,

Thanks for the tip. I am still a year or two away from getting my truck back on the road, so I am still looking for a rebuilder. I talked to Mike's Transmissions in Recedia, Ca. He does classic transmissions and has been in the business for many years. I will give California Performnce a call next week.

Lonnie