The Stovebolt Site Forums The Shop Area Driveline Hydramatic Identication needed - Help!

Having some challenges identifying what a specific hydramatic is from. I know the bellhousing/torus are chevy (v8) but the hydramatic itself I can't identify. Can anyone here? The 4 bolt flange at the rear has me thrown off. Supposedly the trans is a chevy v8. I am no where near the trans, it's in MN and i'm in GA. There is no tag on it.

http://www.flickr.com/photos/101249530@N06/9661918417/
http://www.flickr.com/photos/101249530@N06/9665154168/in/photostream/
http://www.flickr.com/photos/101249530@N06/9661920699/in/photostream/

Thx for any help/guidance in advance!

First, all v8 hydros are out of trucks. I suppose there are some industrial applications as well, but no passenger chevy passenger cars came with hydros.

Second,all 1/2 through 1 ton trucks, (light trucks), had an open drive shaft. Therefore would have a seal for a drive shaft slip joint.

So those are out of the way. The trans in your pictures shows some type of flange that is most likely for bolting to an auxiliary trans or to a closed drive shaft system.

It appears that there is a tag on bell housing in the third picture. If so that could be of help.

I would post on the big bolt page and see if someone has seen this arraignment.

Here's an ad/photo that may have one of the answers to your questions. The seller states that the trans came from an early chevy truck. You can see an "adapter" to what appears to be an open drive line bolted to the end of the trans.

http://www.smartcarguide.com/listing/30705254/



SimS

Hy mphudak, I believe that transmission probably had a propeller shaft parking brake mounted on it, and had a drum with a flange attachment for the driveshaft, I have one just like it, hope that helps.

I am not sure about "hydros", but:
1953 GMC Hydra-Matics had enclosed drive-shafts.
1954 GMC/Chevrolet 1/2 ton truck Hydra-Matics had enclosed drive-shafts.

I wondered about the V8 side of it also. Understood that Chevy didn't put one behind a V8 but what about Pontiac, Oldsmobile, Rolls Royce, Cadillac, etc?

Hy Guys, all Hydramatics with a Chevrolet V8 bellhousing were originally installed in either a truck or a sedan delivery. There are all kinds of examples of V8 Hydramatics, Pontiac V8s in cars and GMC trucks could be bought with a Hydramatic. Oldsmobile and Cadillac V8s used Hydramatics also, hope that helps.

Thx all! The seller did pull some info and it turns out it's from a 1955 big truck, and as someone mentioned the flange was for a parking brake. Pattern looks right for a SBC and the seller removed it from a project w/a SBC. Not ideal since it is geared very low, but price was right so I pulled trigger and bought it. It's complete w/torus, bellhousing and starter so I will find another hydramatic down the road w/better gearing.

For what it is worth, i used freightquote.com for the shipping. Amazing customer service and had a great price quotes. Definitely will use them again for cross country shipping. St Paul, MN to Atlanta was $136.00 for the complete takeout assembly (crated).

If it bolts up for you, I may be wrong but I doubt you will find a great difference in transmission gearing. !st is very low to get truck moving and 4th will be 1:1. There might be a slight difference in the mid-gear spread but I bet not much.

yes, what Greg says, you won't find any other Hydramatic with gearing enough different to be noticeable in use

Bill

This is why I was thinking a different hydramatic. Granted, 1 only lasts for a brief moment, but i'm thinking 2nd would be short as well.

Gear 3100 3600
1 3.82 4.71
2 2.63 3.03
3 1.45 1.56
4 1.00 1.00
R 4.30 6.11

If ya'll think the difference is negligible, i'll move fwd with locating a yoke for the trans i'm getting. That is the only piece missing. IIRC it's larger then the 1/2 ton and is 16 course spline.

What size is a 1955 big truck?

Is it a 1955 GMC or Chevrolet?

Is it 1955 early or late (Chevrolet Advance-Design or Task Force; or, GMC New Design or Blue Chip)?

it's an automatic, just put it in D and go
the only one that matters is high gear, always 1:1

Bill

It's from a 55 2nd series chevy truck, 3600-3900 (black tagged hydramatic). Going in my 55.1 GMC suburban w/a mild 350. Motor isn't my first choice, but it was a new crate motor the PO built and doesn't have many miles (under 10K.) Rear axle I have planned to use is a 55 car, w/3.73 gears. Not ideal gearing but I have an extra 3rd member i'll eventually get different gearing for and swap in.

Long/short, i'm undoing the work of the previous owner. The burb was put on a gbody chassis and the original chassis/drivetrain is long gone. I'm restoring another chassis to swap back in it.

OK...revisiting this as i'm getting some conflicting information. Does anyone know if 3/4-1 ton hydramatics had the parking brake attached to the hydramatic or was this an 1 1/2 ton item? The tag on it has "CHT-55", which I have not been able to find any cross reference what it is from other then a 1955 model. I have found a "CH" refrence, but not CHT.

If anyone has pictures of 3/4-1 ton or 1 1/2 ton+ hydramatics I would appreciate them. I can't find any pictures of these online.

My challenge at the moment is figuring out fact from fiction. All data in manuals/reference material is telling me the black tag refers to 3/4-1 ton trucks. However, i can't find "CHT" code anywhere. The conflicting info i'm hearing is that the 3/4-1 ton did not have parking brake mounted to the trans, that was 1 1/2 and larger, but all the reference material states the tag should be red or another color. Completely confused. S/w one shop that said I can't use this trans w/out substantial modifications but doesn't tell me why i need the mods.

Contact Gene at http://www.restorationhydramatics.com/
He will give you the definitive answer. If the bellhousing bolts up, and the driveshaft mount is the same, I would need a good explanation of why it would not work.

No comment on Gene, but my experience is not the best. I know he is well know for his information but I am hoping to find someone else to clarify the information he has given me. Some of the information has been straight fwd from him, most however has not been and is conflicting.

Understood. Finding someone that is still alive that worked on these transmissions is getting difficult. There are several manuals on-line that cover GMC H-M identification, 54 Chev H-M service, Adjustment and service manuals.

You mentioned much conflicting information. At this point, it is easy to find people that will tell you what they think they know and tell it with authority. That just makes the project harder.

If it makes you feel any better, I have an old transmission service manual and it lumps all H-M transmissions in one chapter. In my mind, that would lead back to my statement that if it fits, it should work for you but I am not willing to stick my neck out and say that for positive.

Hy mphudak, my first old Chevy truck was a 1957 one ton pickup, nine foot box, V8, Hydramatic, the parking brake was a band around the outside of a drum mounted to the rear of the transmission. A flange with a "U" joint yoke was bolted to the output shaft flange, hope that helps.

Try these links.
http://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.html, click on show.
1955 2nd spec PDF page 60 Parking brake mechanical, Looks like Manual & Hydra-Matic tranny had same Parking brake. Drum on Propeller Shaft.
Hydra-Matic transmission identification model guide PDF page 12 & 13, 1940-1956, Cannot find CHT, T might be an error.

You could call these guys ask for John.
Northwest Transmission Parts Give them the cast numbers on the side and CHT 55.

If you look at spec sheet PDF page 6 it shows location of tranny tag, Automatic Left side at (lower) Rear of center case.
Also check spec. PDF page 85, Truck Automatic Transmission

Note: The 1955 2nd spec PDF also has 1955 1st series spec. check PDF page 200 for 1955 1st Truck Automatic Transmission.
The 1955 2nd spec Automatic Transmission page did not scan well.

Thanks,

Thx all! Definitely excellent information to get me back on track and some confidence back in this project.

The T is confusing me and am perplexed by it. I did find an old post on this site that bouymaker posted that he had CHT-55 trans in his 54 truck, but don't know what model truck. I sent him a PM but don't know if he is still active or not.

3B that is exactly what I was hoping to hear! A lot of what i have found talks around the bigger trucks but nothing has confirmed it as you did.

The obsessive part of me is trying to gain all the info and documentation/reference material i can get my hands on. I'm slowly picking up the HM tools as i find them (have all of the necessary service tools/gauges now). Yes HM are dated technology to a lot of folk, but heck our trucks are too. I just hate to see this info be lost for the generations to come. If anything, my lil girl (4yr old) will show the "boys" how it is done in years to come.

Once I get everything sorted out, i'll document the tear down and build up of the trans. It was to have been freshened up 20yrs+ yrs ago and has sat since. I noticed that the TV shaft had little rotation and found that it wasn't properly reassembled. It's clean inside, so I don't know if it was run this way or not. I'm going to proceed though replacing the soft parts and praying none of the hard parts are bad.

Thx again to everyone for the feedback and leads!

This flange could be why i'm told the tail section needs to be replaced to make it usable. I'm waiting on a HM yoke to be delivered, and if it fits I will see if i can find a seal that works or if I need a little machining is in order.

I'm assuming the flange was a slip yoke since on mine i see no provision for a bolt in the output shaft.

Hy mphudak, the output flange on my transmission was bolted in place, and the output shaft had a very coarse spline, not fine like a slip yoke spline, hope that helps.

Hmm...looks like more digging then. My output is a coarse 16 spline and appears to be slip yoke (based on not having a threaded hole). Would make more sense for it to be a fixed yoke w/the parking brake assy.