The Stovebolt Site Forums The Shop Area Driveline Hydra-Matic anyone?

I taint twistin’ any wrenches yet, just trying to get all the pieces together and some of the
leg work out of the way.
But, I’m planning a little reverse engineering to my ’54, 3604, by that I mean I going in
the opposite direction that most guys do and switching over to the Hydra-Matic
I almost got all the original parts I need out of a 55 1st, 3104. What I haven’t gotten I’m
pretty sure I can copy and fabricate.
The questions that I woke up with at 03:00 this morning concern the differences between
the 1954 and 1955 1st. Hydra-Matic setup and the difference between the 3104 and the
3604 of the same years.
From what I’ve been able to sort out, the 1954, 3104 still had an enclosed drive shaft and
the rear of the automatic was supported at a rear cross member. I got that from Tim’s
pictures on his web page.
The 1955 1st, 3104 apparently had been switched over to the open drive shaft, my guess is
in preparation for the new ’55 2nd TF’s with their stock open drive line. I got that because
the Hydra-Matic set up that I have out of the ’55 1st had an open driveline.
Now, the 1954, 3604 4speed SM420 simply hangs off the back of the bell housing and is
not supported at the rear.
Question: was the ’54, 3604 Hydra-Matic supported at the rear like the ½ ton and was the
55 1st, 3604 the same?
I’d really appreciate any input or pictures of either or both the 54 or 55 1st ¾ ton Hydra-
Matic trans installations especially the rear mount and cross member if there was one.

Also, it appears and I’m assuming that the Rochester is the same for the standard and
automatic. Any discrepancy to my observation about that?

If I remember correctly Greg and Tim have posted that the master cylinder is also
different and I’m wondering how they took care of the single peddle vs the two. Either
they used a different shaft or spacers?

I will be posting to the Swap Meet for a few items like an automatic trans cover, original
push button, master cylinder and probably a few others.

Now I just know you guys are running for your cameras, so let me thank you before
hand.
Denny Graham
Sandwich, IL

Denny,

The Rochester for a hydra-matic truck had an automatic choke with a heat tube and "cover" over the exhaust manifold. I think I have some pictures if they would help you out.

I am not completely sure about a different master cylinder. I think there may be a difference in the end fitting but the biggest difference was in the brake line routing. The H-M routed farther back so it did not cross under the transmission so that the trans could be reoved from under the truck without the brake lines being in the way.

You know Tim is probably the best source of factory info you will find. The starter button color question will come up later. Obsolete Chev insisted that a cream colored button was correct. Others say chrome (in 54 55 1st) Personally, I went with black knowing it was incorrect but I felt it to be the best match to all of the other black knobs.

I found a thread on classicparts.com about a 54 H-M driveline "up for grabs" I don't know what all would be available but it is a lead for you if you want it. Also Cletis called me yesterday with a H-M trans for sale with an open driveshaft tailhousing. I don't know if anything else was available but again, it is a lead if you choose to follow it up.

Denny,

The 235 Hydra-Matic Rochester carburetor has an automatic choke heated by a heat tube to a manifold-mounted "stove"

The front fitting on the H-M 1/2 ton master cylinder is different. The diameter of the hole is different (I'll look for photos). There was a split block on the front. Lines were mounted differently - so brake lines were not under the transmission and rear of the engine (in case the transmission had to be removed).

The pedal shaft is different/shorter.

Greg & I know a person with an unmolested 54/55 3/4 ton GMC pickup (I forget which series). There were minor differences between 1/2 ton 54 GMC and Chevrolet Hydra-Matic equipment. But I do not know if the differences were only in the shift-linkages/indicators.

Greg will remember the color of the push button on the dash (my guess is black button on 54/55 Chevrolet).

Too bad there is not a GMC Master Parts Book on line.

Did you get the H-M solenoid starter with your transmission?

You bet Greg, any pictures would help. The carb I can probability find but any stove that
I would find would be half rusted away. That could be fabricated also If I had a picture to
work from.
I have a “ran when I parked it” Transmission. Supposed to be a good one. It has an open
drive tail-housing, and that was what one of my questions was referring to. I was told that
the 55 1st , 3104 Hydra-Matic was an open drive shaft, but the ’54 was still an enclosed
drive shaft.

This is a Chevy I’m talking about Tim, not a GMC. Pete has loaned me his bell crank and
throttle linkage from his ’53 GMC ¾ ton and it is different than the Chevrolet bell crank
and linkage. His GMC was changed over to an SM420 many long years ago.

The starter push button isn’t all that important. Push buttons are available for many
applications and they could be fabricated or modified to look just like the original. My
guess would be that it was black also and the white ones that Tygert has pictured in his
online catalog are most likely for passenger cars.

I haven’t gotten the starter yet but it’s still supposed to be coming, along with the throttle
bell crank and up-rod. I haven’t seen it so I don’t know what condition it will be in or if it
well even be usable. If I get that then the trans cover is the only really big thing that I
would need to find or fab (hope to modify the 4speed).

Rerouting the brake lines is a no brainer, but what’s with the “special fitting?” Was it to
split the lines from the front to the back??? Someone gottum picture of one???

One of the most evasive and puzzling parts of this is whether there was a rear support
cross member used on the ¾ ton truck transmission tail-housing. I have yet to see a ¾ ton
equipped with an automatic even in person or in pictures.
Sure wish I knew some Bolters that lived around me.

Denny G
Sandwich, IL

I realize you have a Chevrolet, not a GMC. But some of the parts might be the same - MPBs would confirm/dispel that possibility.

This 1929-1957 MPB only show a H-M transmission rear support for 1954 1/2 ton.

I was wrong on the Master Cylinder. The hole is bigger but there is no T-block on the 1/2 ton H-M/MC. A large diameter line goes towards the rear of the truck, to a frame cross-brace behind the transmission, to a T on the passenger side. That T sends one smaller diameter line to the front brake T and one smaller diameter line to the rear hose bracket on the frame rail.

I can take photos, if you think the 1/2 photos are of any use to you.

Let me know if you want me to send you a transmission-opening floor cover to use as a model (to mark the opening in the floor-board/toe-board, and for the accelerator pivot-attachment).

Denny,

I sent some pictures yo the e-mail address that is listed on your public profile. I will send some more pictures that might help answer some questions.

I have a carburetor that is mentioned above. I pulled it from a truck years ago. PM me if you need info

I don't remember any rear mount on a hydramatic in the TF series, I'm sure they just hung off the engine like all the other transmissions did. The flywheel housing (bellhousing)had the rear mount points on it.

Not yet Tim, just gatherin' up info and parts to keep right now. But as we talked about, I
might just take ya up on that if I can't find a junker. I'll bet Brad has had a few HM's slip
thru his hands. He's had enough trucks over the years.

If you're referring to the gp.4.081 pn.3710610, I believe that's the bracket that you have
the pictures of on you web page. I didn't see a cross member mentioned. Since the cross
members are all a permanent part of the frame I would not think any of them would be
serviced separately. I just want to know if there was one in the HM equipped ¾ ton
trucks.
The HM and the SM420 aren’t to far apart as fur as the weight goes so I suppose it would
be possible to hang it from the bell housing like they do with the 4speed. The main reason
they have a rear mount on the ½ ton is because of the torque tube. The ¾ ton trucks have
a center support so there really isn’t any thing hanging off the back of the transmission.
I’ve got the front cross member that supports the engine from the ’55, 3100 and it
measures 23 ¾” across. My ’54, 3600 front cross member measures 32 ¾” across so the
frame has a wider stance than it’s little brother.

Just took a look at the pictures that you sent Greg, thanks. Like I said, the stove looks
easy enough to fabricate. It looks like it wraps around the manifold and is pinched
together at the bottom? It would appear looking at the picture that there is a boss cast into
the manifold that the stove is screwed into but I doubt that the manifold would be
different than the standard shift.
Good view of the ‘B’, now I’ll know what to look for next time I make it to a swap meet,
thanks for that. And I’ve got all the parts for the shifter box like in the picture you posted.

Denny G

The 4-speed weighed 70lbs over the 3-speed, and the H-M weighted 70lbs over the 4-speed (from the 1954 Truck Tech Specs manual).

There is the big difference. The H-M crossmembers are not only beefier, they have provisions to unbolt from the frame rails so that the trans can be dropped from under the truck.

The crossmembers are not as permanantly mounted as the standard transmission versions.

Maybe we are not communicating clearly.

"Since the cross members are all a permanent part of the frame I would not think any of them would be serviced separately. I just want to know if there was one in the HM equipped ¾ ton
trucks."

Denny, did you know that two 1/2 H-M frame cross members came from the factory bolted, not riveted, to the frame? I do not know what s"serviced separately" means, but Maybe we are not communicating clearly. "Since the cross members are all a permanent part of the frame I would not think any of them would be serviced separately. I just want to know if there was one in the HM equipped ¾ ton trucks." Denny, did you know that two 1/2 H-M frame cross members came from the factory bolted, not riveted, to the frame? They may not be "serviced" by GM, but they were only bolted on..

You'll see a specific 2nd cross member listed for 1954 1/2 ton H-M trucks (group 7.011). I am still looking for a listing for the third cross-member on a 1/2 ton 54 H-M truck. There is nothing like a mystery, to keep us scratching our heads?

The Factory Assembly Manual shows the various cross members

The "serviceable" part I gave above is the cross member at the rear of the 1/2 ton's Hydra-Matic transmission.

The "cross member" under the 54 rear motor mounts is called an engine rear support (Sect. 2, Sheet 9), part number 3703340, 7.229 (same part on 3100 & 3600). I'd bet that these were bolted for 1/2 ton H-M trucks and riveted for standard transmission trucks (I'll not bet on the 3600 H-M trucks).

Tim, you have e-mails on the way to you. I am sorry that I was unable to scan the pages so I just took pictures of the pages. I hope it helps you with the individual crossmembers. The good news is that it shows the 1/2 and 3/4 ton crossmembers as the same for A.T.

I am ready to now bet on the 3600 and 3800 engine rear supports being different for H-M equipped 1954 trucks (I do not gamble - gamblers can lose):

Here are the LH and RH engine support brackets that get riveted to the side rails on 1954 H-M trucks; and, they get bolted to the "center" support member under the engine rear mounts. It also lists the separate H-M "center" support member (used on 3100, 3600, and 3800 H-M trucks).

Greg,

I have received your photos. I think I have already linked to the MPB entries you sent.

What MPB/etc did get the frame illustration from? It is blurry, but if it is on-line, I'll post it; or, if I have the MPB, I'll try to get a better scan.

Thanks,

added later
Here is the general truck frame illustration from the Master Parts Book.

I sent you a clear picture of the frame shot. I didn't realize how blurry the first one was until it had been sent. I shot it a few more times until I got one I liked. You should have it now.

Ok, now I'm reallly cornfused, this is gonna take a while for me
to digest what you all are sayin'.
dg

Think about it this way. You can unbolt and drop a manual transmission from under the truck easy enough. Not so with the H-M if it was designed to go in the same way. So, they designed it so that the engine could be removed leaving the trans in the truck and then dropping the trans from underneath. Or they made a tool to hook on the frame rails to support the rear of the engine and the trans could be removed while leaving engine in. To accomplish that, they needed access to the "bellhousing bolts" which is why the transmission cover is different. Then, there needs to be a provision to drop the transmission which is why the made bolt in crossmembers that can come out with the transmission or just be dropped to be out of the way. Same reason fro the brake line re-routing. It was all done in the name of serviceability.

Didn’t know that you could have ordered the individual frame parts, that was a real
surprise.
Well as usual, what I thought was going to be a clarification of the two examples of
Hydra-Matic options has turned out to be a knarled up ball of string. What I really need to
do is find one of each and take a whole rash of pictures so I can compare them to each
other. The parts books simply muddy up the waters more than it already is.
Example one: 1955 1st., 3104 H-M (H-M truck)
Example two: 1954, 3604 H-M (H-M truck)

The glimpses thru the fog that I do see tells me there was a lot more variation in the
standard vs the Hydra-Matic trucks for 1954-55 then is commonly known. And that there
is a lot more variation in the crossmembers between the 1/2 ton vs the 3/4 ton. None of it
apparently is going to be clear till I can actually crawl under and take some
measurements and pictures in person.
I do appreciate the effort guys, and I'm sorry if it didn't sink in, but this feels like the old
exercise we did back in 4th. grade. The one where the teacher whispered a story to the
first person in the right front desk then we passed it on back to the person behind us till it
got to the last person in the room. Of course the first and the last were two completely
different tales.
I simply can't see how the 23 3/4" crossmember from the donor 1/2 ton could possibly fit
in the 32 3/4" wide frame of the recipient 3/4 ton. And I can't see how the frames under
the cab could be so much different in width since the cabs mounting points are the same.
http://www.pbase.com/dennygraham/image/148948058 There must be another short
bracket on each side that’s riveted to the frame on the Hydra-Matic trucks.
That still wouldn’t explain how the rear of the trans would have been supported on the ¾
ton trucks, if in fact it was.

I was really hoping that someone with a ¾ ton H-M would jump in here with some
pictures but they must really be rare old gals.

So thanks again, but I gotta get the mutt on her leash and head out for our morning
constitutional.

Denny Graham
Sandwich, IL

Okey dokey, Had lunch with Pete today and he brought along his FAM and pointed out
that it documents the R.P.O. in detail. So the mud has been cleared from the lens and I
can see clearly what’s going on. My FAM is still packed away in one of the boxes from
the move I made this past year. But section 7 of the FAM is devoted mostly to R.P.O.
314, which was the H-M option.

There is a left and a right bracket pn.3707655 & 56 that are permanently riveted to the
frame. The engine rear support crossmember pn.3707659 (23 3/4") is bolted to them; this
applies to all of the 3000 models.

At the rear of the transmission there is what is called the “second” crossmember
pn.2296067 shown for the 3100 models only.
It seems clear that a crossmember is not used at the rear of the transmission on the
3600-3800 model frames. The crossmember, which is called the “second” crossmember,
is further back and is where the center support bearing is positioned on these models.

The brake lines are shown running straight back on the left to the 4th or, gusseted
crossmember then across to the right side where the split to front and rear are made.
pn.2286293 Spacer fills in where the clutch once was on the pivot shaft of the pedal
bracket.

Denny Graham
Sandwich, IL

Well-described, Denny.

I'll have to look for the spacer on the pedal pivot-shaft (that might be why I thought it was a different shaft). I think I have that shaft off and primed/painted.

Im trying to find out what the gear ratio for a 1954 GMC Hydromatic would be. 1/2 ton & 3/4 ton.
Any info out there?

unless you mean the rear ratio, gear ratios of the Hydra-Matic

Bill

Yes, the rear end.
I have a rear end that came out of a 54 GMC Hydromatic but I dont remember if it was out of a 1/2 or 3/4?
Javier

3.90:1 for 1/2 ton GMC & Chevrolet Hydra-Matic (not Hydro).
4.57:1 for 3/4 ton on both, I think.

Is the rear of your Hydra-Matic made for an open drive-shaft (exposed u-joint) or for an enclosed drive-shaft (enclosed u-joint)?

Tim & Bill thanks for the info.
Yes the rear end is an open drive.

Javier

If you have an 1954 transmission, that would be a 3/4 ton or 1 ton transmission.

Is there a code plate on the transmission? If yes, post the code.

And, if there is a plate on the flywheel cover, post that.

Finally, if there is a code pressed into the block, to the rear of where the distributor goes into the block, post that also.

All I have is the 6 lug rear end from the GMC hydramatic.
I'll look for any stamping on the rear end & post tomorrow.
Thanks
Javier

One more clue could be the color of the oval tag on the transmission. The half ton would have had an orange tag in 54.

Here is a picture of brake line.
Junction T-block
Junction T-block Zoom

If I am not mistaken didn't the 3/4 ton have a 2 piece drive shaft with a center intermediate bearing?
If it did, wouldn't that eliminate the need for a Hydra-Matic rear tail support cross member?
It is kind of strange that they would let that much weight hang out like that with no rear support.
Although there is a lot more stress on the enclosed drive train Hydra-Matic tail housing than the open drive train Hydra-Matic tail housing.
Hence the need for a rear tail support cross member.

I do not recall ever seeing a 47-55 1st manual transmission with a rear tail support cross member.

Thanks,

Group 4.081 48-53 all 1/2 ton; and, 1954, only 1/2 ton with H.T. (HydraMatic Transmission)

I stand corrected.
So that would mean 47-55 1st Hydra-Matic and manual transmission trucks 3/4 ton and up with a open drive shaft, do not use a transmission rear tail support cross member.
Do trucks 3/4 ton and up use a 2 piece drive shaft and a center carrier bearing?

Thanks

First off lets correct this, the Hydra-Matic was first offered in the
1954 Chevrolet model year trucks, not before then.

Second, the 1/2 ton trucks, whether Hydra-Matic, 3sp.or 4sp manual, had a rear
transmission support and were enclosed drive shaft up to and including 1954.

Third, all the 3/4 ton AD's had two piece drive shafts with a center support.
Prior to '54 the front drive shaft was enclosed and the rear open.
1954 and later had open drive shafts front and rear. None of the 3/4 ton manual
transmissions, 3sp.or 4sp. had a rear transmission support or cross member.
With months of searching behind me, I've been unable to find anyone who can supply me
with a picture of an original 3/4 ton that had a factory installed Hydra-Matic. So I cannot
say with any confidence whether the 3604 with the Hydra-Matic option had a rear
transmission support and cross member.

I have reason to believe that the 1955 1st. 1/2 ton with factory installed Hydra-Matic
had an open drive shaft. This I have not been able to confirm since I've not been able to
find a stock 1955 1st. 3100 with a factory installed Hydra-Matic to date.
The 1955 1st. 3104 that my Hydra-Matic came out of had been modified over the years
so I have no way of telling if it was factory correct. The transmission case does say it’s a
1955 and it does have an open drive shaft rear housing.

I also cannot confirm whether the 3105 rear transmission mount and cross member are
the same as the 3104. From what little information I've seen, they appear to be the same.

That sound correct Tim or Greg????

Denny Graham

That almost looks good to me, Denny.

"Second, the 1/2 ton trucks, whether Hydra-Matic, 3sp.or 4sp manual, had a rear transmission support and were enclosed drive shaft up to and including 1954."
- Only the 1/2 ton Hydra-Matic 1954 trucks had a rear transmission support. All other 1954 1/2 ton trucks (with manual transmissions) had no rear transmission mount (a rear transmission mount was used on earlier 1/2 ton Advance-Design trucks).

Questions:

"First off lets correct this, the Hydra-Matic was first offered in the 1954 Chevrolet model year trucks, not before then."
- Why did you state this - did someone post something different?

"I also cannot confirm whether the 3105 rear transmission mount and cross member are the same as the 3104. From what little information I've seen, they appear to be the same."
- What would cause you to doubt this? panel vs pickup?


This post might be boring to non H-M members. It has been a good exercise for those of us who like to see/know the facts/documentation, before we start to speculate on the gaps in the documentation.

This has been a discussion of the Hydra-Matic transmission in Chevrolet trucks. GMC Hydra-Matic history differs from Chevrolet.

GMC started using the Hydra-Matic transmission in domestic (non-Military) trucks in one 1952 model (150-22, 3/3 ton delivery/step van) and in all small GMCs (1/2-1 ton) in 1953, and some real interesting Hydra-Matics in big GMCs in 1954.

I thought someone mentioned that the Hydra-Matic was in the 47-55 truck, maybe I missed something or am thinking of another convoluted thread. This thing seems to has taken on a life of it's own, where a few pictures of original trucks would go a long way to resolve it. When it comes to compairing Chevrolet and GMC trucks I don't even want to get into that. That would add a whole new level of confusion to the kettle.

I'm not fortunate enough to have a '54, 3100 manual transmission truck in the barn that I can look at, since the enclosed drive shaft was still being used in '54 I just assumed that it still had the rear transmission support as all the earlier enclosed 1/2 ton trucks did.

Yes, this sort of nit-pickin' post will probably be boring to members that are just interested in getting their vehicle on the road and couldn't care less about the authenticity or originality of a restoration. But I'm not one of those.

The fact that I don't have an original 3105 panel or 3104 pickup sitting in my barn that I could crawl under and confirm that the frames are the same is the reason that I posted that Tim. As I said, from the few sketchy pictures that I've seen, they appear to be the same. I also haven't found any pictures of the manual transmissions in original '54 and '55 trucks, just as I haven't found any pictures of '55 1st. Hydramatic 3104's or 3604's.

and as usual, I can't open your: page%3D1&title=Hydra-Matic%20anyone%3F%20-%20The%20Stovebolt%20Forums&txt=no%20rear%20transmission%20mount&jsonp=vglnk_jsonp_13627552340156 link

or your: http://api.viglink.com/api/click?format=go&key=e1b970c476aad3dffc4271e7911b4c7e&loc=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dshowflat%26Number%3D922440%26page%3D4&v=1&libid=1362753748918&out=http%3A%2F%2Fwww.1954advance-design.com%2FDocuments%2FEngineeringFeatures%2Fslides%2Forig_Page39.html&ref=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dpostlist%26Board%3D49%26page%3D1&title=Hydra-Matic%20anyone%3F%20-%20The%20Stovebolt%20Forums&txt=earlier%201%2F2%20ton%20Advance-Design%20trucks&jsonp=vglnk_jsonp_13627552781718 link.

Don't understand why you can't just cut and paste a link like this to the thread: http://www.pbase.com/dennygraham/1954_3604_chevy_truck
hasn't failed to work for me on anybody's computer or browser.

Denny G

Tell me if these work, Denny (I doubt they will work for you)

http://www.1954advance-design.com/Documents/EngineeringFeatures/slides/orig_Page51.html

http://www.1954advance-design.com/Documents/EngineeringFeatures/slides/orig_Page39.html

Same old same old:

http://api.viglink.com/api/click?format=go&key=e1b970c476aad3dffc4271e7911b4c7e&loc=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dshowflat%26Number%3D922440%26page%3D4&v=1&libid=1362768466745&out=http%3A%2F%2Fwww.1954advance-design.com%2FDocuments%2FEngineeringFeatures%2Fslides%2Forig_Page51.html&ref=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dpostlist%26Board%3D49%26page%3D1&title=Hydra-Matic%20anyone%3F%20-%20The%20Stovebolt%20Forums&txt=http%3A%2F%2Fwww.1954advance-design.com%2FDocuments%2FEngineeringFeatures%2Fslides%2Forig_Page51.html&jsonp=vglnk_jsonp_13627685202036

http://api.viglink.com/api/click?format=go&key=e1b970c476aad3dffc4271e7911b4c7e&loc=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dshowflat%26Number%3D922440%26page%3D4&v=1&libid=1362768466745&out=http%3A%2F%2Fwww.1954advance-design.com%2FDocuments%2FEngineeringFeatures%2Fslides%2Forig_Page39.html&ref=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dpostlist%26Board%3D49%26page%3D1&title=Hydra-Matic%20anyone%3F%20-%20The%20Stovebolt%20Forums&txt=http%3A%2F%2Fwww.1954advance-design.com%2FDocuments%2FEngineeringFeatures%2Fslides%2Forig_Page39.html&jsonp=vglnk_jsonp_13627684908754

DG

Works ust fine when I use this link:
http://1954advance-design.com/

Punch in the one you have at the end of your replys and this is the crapola that I get:
http://api.viglink.com/api/click?format=go&key=e1b970c476aad3dffc4271e7911b4c7e&loc=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dshowflat%26Number%3D922440%26page%3D4&v=1&libid=1362768972856&out=http%3A%2F%2Fwww.1954advance-design.com%2F&ref=http%3A%2F%2Fwww.stovebolt.com%2Fubbthreads%2Fubbthreads.php%3Fubb%3Dpostlist%26Board%3D49%26page%3D1&title=Hydra-Matic%20anyone%3F%20-%20The%20Stovebolt%20Forums&txt=1954Advance-Design.com&jsonp=vglnk_jsonp_13627690133122

I can't be the only one in the world that has a problem with your links.
DG