702 GMC V-12 powered '62 GMC 1-ton

[cayoterun]

Very good! I finally got both trucks home and it's sure worth considering using the present 131" frame. I could live with that for my purpose.
Kinda at a stand-still. Trying to find clutch/tranny set-up before going further.
Still run "Balaur" a couple of hrs each day.
Thanks a million,
Cayoterun

[Pyrotechnic]

Ever considered an automatic ? Something like an Allison 545 4 speed out of a school bus might works though I have no idea what bellhousing pattern a GMC V12 has.

[watahyahknow]

try sending an email to the blastolene brothers there newest car has the same engine in it and they prolly can tell you wich trans will work .
its originally based on a 6 cylinder gmc so i wouldn't be surprized if that gearbox matches the block

[dwcsr]

If you can get hold of a Sundstrand Hydrastatic transmission they will bolt up to the V12. They used them in some trash haulers in the 70's

[FRENCHBLUE72]

Very cool engine build up..

[89 crew]

Sundstrand also gave a lifetime gaurentee for commercial service on all of their truck transmissions! They also gave 2-3mpg better mpg than anything else. the bad news is you probably won't find one. how big is the flywheel that was on it? as I recall the 478 and maybe the 401 could run a 13" clutch without an adapter. the rest I thought were limited to a 11" till the adapter plate was added?? find, or make the adapter plate, and bolt what ever transmission you want to, to it. I would recommend either a 400 or bigger! I think that will twist a 700r4 into a knot and laugh while doing it!

[cayoterun]

Most 702s (or all) that were used in trucks had a 16 1/2" dia. flywheel/w 1 1/8" dish, larger flywheel housing, bigger starter, and a double-disc 14" clutch-pressure plate.

This engine was used as a stationary (agri. irrigation pump) power plant. It never had a clutch. The driveshaft flange was bolted directly to the flywheel.
It has a 15 1/2" flywheel/w 1 1/8" dish, smaller flywheel housing and starter.
I have a factory maintenance manual that says that on irrigation motors, there is an optional Lipe-Rollway 14" single disc clutch-pressure plate and gives Lipe-Rollway part#, as well as GM part#.
A local parts house says they can match the clutch and pressure plate, so after the holidays,I plan to order one. When I get one in hand and know it will fit, then will start looking for a tranny. I have a tranny & bellhousing from a 401 truck that will fit, but it is 5spd direct. It used a 13" clutch and had a flat flywheel. Clutch won't fit.
I need a 5spd OVER tranny and faster rearend gears to get 2400rpm max engine speed up to inter-state speeds. A direct tranny and 4:10 rear gears only give around 55mph @ 2400. I'd sure like to get geared to 60-65mph @ 2000rpm to go easier on the old motor. It will never be abused in any way and not intended for a DD or hotrod.
I've looked at the auxilary trannys, but really don't have enough space to get it all under there.
I'm trying to get to a 5spd over manual tranny and some 3:21 or so rear gears to save space.
There are some 5spd over trannys listed, but first step is having a clutch set-up, in hand and installed before the tranny search.

"Balaur" has had about a 100 gallons of propane run thru it, so far. Running much better, but will always be a smoker, and oil drinker. Would be nice to have new overhaul kit available, but that's history.
Thanks for all the imput and interest.
As stated in past, this may never fly, but it's the challenge that's fun, and we have a running piece of GMC history. Someday, it may be donated to a nice museum not far from here for permanent display, since so many of them were used on irrigation wells.
Cayoterun

[89 crew]

you said it has a 14 " clutch? that is the same size the 91 427 gmc topkick has. don't know if that will help but I would check a eaton roadranger presure plate to the flywheel. The disk is determined by the splines on the transmission. The only thing left is the throw out bearing, and that can be worked around.

[cayoterun]

Yes, 14", 10spline, 1-1/2 shaft, 1" pilot bearing bore/w 12bolts for pressure plate to flywheel.
I've never seen a clutch & pressure plate for a flywheel/w a dish in it.
I do have a good throw-out bearing.
I hope in a couple of weeks, I can get one thru our parts house. I did ask about return, Just in case, and it would only cost $40. restocking fee.

An interesting V-12 tidbit:
The claim is that all V-12s were hand built in the factory floor. Each piston was hand fitted, honed and numbered, etc. The V-6s did go down the production line. I wonder if there is factory documentation out somewhere.

[jeffspower]

That flywheel is for a double disc clutch. The holes around the outer ring are for "dogs", they locate a steel center plate between the 2 discs. I don't think you will find a single disc clutch that will work with it. Typical clutch setup on an old 210hp 3208 CAT, & many others. Were there ever flat flywheels for the V12? If not, you will probably have to run the double disc and a tranny with a long input that is intended for it. Even if you went Allison, all those I have seen used a flat flywheel. Also, there are a couple sizes of "SAE" clutch housings (the round opening). Yours looks like a bigger one. From what I remember, 3208 CAT, DT 466 IH, 555 Cummins and 4-53, 4-71 Detroits had the small opening. 6-71 detroits & most larger truck engines had the big opening. But with the big opening on a truck, you usually found a double disc 15" clutch & 1-3/4" or 2" input. 14" with the small opening and 1-1/4", 1-1/2" or 1-3/4" input. Then there are push & pull type clutches. The bellhousing (and possibly the input shaft) will dictate what you need. I bet it will be tough to find anything other than a Roadranger with an input shaft that will work with a double disc.

What do you have for truck parts guys there? A place like Inland truck parts could fix you up with the right stuff for sure.

Here's a pic of a 14" pull type cast iron pressure plate double disc Spicer clutch.

[jeffspower]

Here's a bellhousing chart I found:

[89 crew]

You need to find a GOOD clutch shop for this not a parts store. If you were here in Ks I'd send you to Casper brake and clutch. They could hook you up! The first thing I would do is turn that flywheel and get rid of the second disk. make it a single disk with a standard cover. you would have to chang throw out bearings but that isn't much. Make sure your throw out bearing is greasable. some are, some aren't. it is a PITA to pull a big transmission over a little bearing!

[cayoterun]

V-12 quirks!

This is the double disc flywheel & housing that was originally on my motor. The flywheel, housing, and starter are all bigger. This flywheel has the "dog" notches for the center metal clutch plate. It weighs, maybe, 10# more than the small one I switched too. It is 16-1/2" dia. There were a few that used these, but the old mechanics would ask if your motor had a big starter, or small. I chose to change to the smaller stuff due to greater availability in the junkpiles.
Crew: Our closest towns of any size are at least 100mi away. However, I'm in the middle of a vast amount of knowledge of our local parts houses and older mechanics due to the engines popularity in their heyday. Mainly the engines. The automotive side is uncharted waters for us.
This type thing is where you guys are really helpful and appreciated. I called a clutch place the other day, and when I told him what I was looking for, he told me he had never hear of such a motor and was sure they didn't have anything. Not a new response other than areas they were used, and the younger people just don't know they existed. Not their fault.

Jeff: Thanks for the chart! I just measured all three housings, they are all SAE #4.
GM definitions: For my benefit. I'm used to one piece bell housings.
Flywheel housing: Bolts to engine block and starter mounts in it.
Bell housing: Bolts to transmission, then mates to flywheel housing.
Both flywheel housings have same bolt pattern. Difference is the larger one is just cast with a bigger bulge for the starter to accomodate the bigger flywheel. Tranny bellhousing will fit both.

My GMC maintenance manual gives these #s as optional for V-12:
Pressure Plate:
Lipe-Rollway 14" single disc
Type: 14DTB
Model# stamped: 140-61-811
GM# 2452571

Clutch disc:
Lipe-Rollway# stamped: 140-6-119
GM# 2456718

Hope someone has an inter-change manual in their archives.
Thanks,
Cayoterun

[cayoterun]

Morning, Folks:
Educate me some more. I've never worked on anything bigger than bob-tail grain trucks, nothing big like this.
#1: What's the difference between a push and pull clutch?
#2: Jeff, in your pic of the new clutch, What sequence does those three pieces go.
Does the clutch disc (left) go first against the flywheel. Then center plate (right) is next, and does it have friction facings (other side, not showing) to engage the bottom pressure (blue) plate when bolted to the flywheel ring?

In the V-6/V12 maintenance manual, the double disc diagrahm shows 1 disc against flywheel, smooth steel disc/w dogs in flywheel notchs, another disc, then pressure plate bolted to flywheel ring.

I'd sure like to find a junked V-12 truck with clutch and housings still there to see how it fit and buy, maybe, just for a road map for these things.

We do have several good truck repair shops here, but when I ask about these motors, they just shake their heads, so feel like it's down to us trying to blaze new trails on old stuff.

I have looked into the automatic stuff, and it's so pricey, I can't afford to put that much in an old, maybe unreliable motor, for toy use.
Thanks,
Cayoterun

[watahyahknow]

Originally Posted by cayoterun

Morning, Folks:
Educate me some more. I've never worked on anything bigger than bob-tail grain trucks, nothing big like this.
#1: What's the difference between a push and pull clutch?

a (hydraulic) push clutch is mounted to the bellhousing and pushes at the arm operating the release bearing
a hydraulic pull clutch is mounted on the engine and pulls the arm towarth itself

since the clutch is so big i take it would've been hydraulic operated

[cayoterun]

I have a 401 set-up, from a cab-over. It's a push with the hydralic slave unit on the bell-housing/flywheel housing.
I have a friend in Wis. with a restored V-12 cab-over, so will ask him how/where it works on his. That can be seen from the outside.
All this sure helps.
Thanks, watahyaknow.
Cayoterun

[jeffspower]

Originally Posted by watahyahknow

a (hydraulic) push clutch is mounted to the bellhousing and pushes at the arm operating the release bearing
a hydraulic pull clutch is mounted on the engine and pulls the arm towarth itself

since the clutch is so big i take it would've been hydraulic operated

Well, yes and no. The Spicer "big truck" push type clutch uses a typical throwout bearing design that pushes on the pressure plate diaphram (or levers) just like an automotive clutch, but the Roadrangers & some others don't have a typical automotive fork. It is a rotating cross shaft that goes from one side of the bellhousing to the other. It has fingers extending from it that push on the throwout bearing. A pull type clutch TB is mechanically attached to the pressure plate levers, and is pulled away from the pressure plate, instead of pushed. It uses a cross shaft too, but with fingers that pull instead. The pull type is the better & longer lasting design.

"In the V-6/V12 maintenance manual, the double disc diagrahm shows 1 disc against flywheel, smooth steel disc/w dogs in flywheel notchs, another disc, then pressure plate bolted to flywheel ring."

Yep, that's how it goes. Each disc needs to be installed as marked. the spring dampened center sticks out towards one side, and will cause havoc if put in wrong. And yes, the lining is on both sides.

[cayoterun]

Thanks, Jeff.
This is a push, with the conventional fork on throwout, with hydralic slave to push on the lever.
If this thing ever moves under it's own power, you've got to come and drive it out of the shop for it's maiden voyage to the mailbox and back.
Cayoterun

[Pyrotechnic]

I got another idea for you as far as engine placement.

The engine and trans would be in the bed of the truck, but you would use a 4x4 transfer case on the trans. For the rear axle, you would use a 4x4 front axle with the tie rods locked. This is about the most compact way I think of to place this drivetrain while still keeping a normal looking truck.

Now, I'm not sure if the engine, trans, and transfer case would fit in a long bed truck or not. If it all fits in the back of a long bed, this would work real well for you. If not, you could use the crew cab but you would have to use some of the rear cab space for the engine.

The only problem is if you want to use a manual trans. I'm sure you could come up with some kind of cable shifter setup like on FWD cars. If you use an automatic, it would be easy with this setup.

Here's a pic to give you an idea.

[watahyahknow]

this has been done before actually my idea was kinda the same but i would point the gearbox towarth and underneath the cab making it eazier to shift too then take the 4x4 trasfer case and route the driveaxle back to the rearaxle again , this btw leaves the old motorspace available for the extra radiators if needed and propanebottles too

wheelstanders do the same thing but use a V drive out of a powerboat

[cayoterun]

Keep the ideas coming. As I talk and compare, Things keep showing up, that will bolt up. I'm trying to stay as near bolt on without expensive machine work as I can. We may wind up with parts off John Deere tractor, Farrari cars, and Peterbuilt trucks, BUT, if we get something put together that available, then it will be easier for some of us to put another together sometime. I'm also trying to stay "low-budget" and simple as possible. I can already see, that with my limited abilities, that the cosmetics will be uuugly and patched together. Just so the driveline, suspension, and brakes are well put together, and safe.

We're taking a "time-out" for a funeral in NM for a great long-time friend who happened to be my bro-in-law.
Thanks to all of you.
Cayoterun

[watahyahknow]

the thing i've drawn out here will need the diff housing to be off centre .
you might be able to get around that by using a chassis cab (14 bolt) axle thats too narrow to fit under a stock dually bed (it does fit under a stock bed without the bulges and with deeper inner fenders ) and add a big spacer on one side to even it out again
it will be hard on the bearing on that side but then again those bearing are capable of taking quite a load from the trailers and all the other stuff that usually gets loaded on the truck and you prolly need to move one of the springs inbourd or the springperch out on the axle .
it will be about 6 inch off centre you need i guess to get it to connect to the driveline running next to the engine .
the good thing with this idea is that you dont need the long nose and frame , those stay stock (as long as you can run the drive line under the chassis ) you prolly need to make a big transmission hump to get the stuff to fit and you have the engine on permanent display , if you need to par it outside a stock eeeh canvas roofthingy will prolly fit over the engine making the truck look stock untill you start it up

[watahyahknow]

just thinking about the trans if you mount the engine solidly and the trans too in the same frame i don't see why it needs to be mounted to the engine you could use any trans thats strong enough and make a small transferaxle from the clutch on the engine going to the trans it will be fast reving so you need to balance it

[Pyrotechnic]

Also, if you do the front 4x4 axle in the rear idea like I posed the diagram of, you could use something like a 6 lug 10 bolt which would give you the option of 2.73 or 3.08 gears. I know it's not the strongest, but if you are just making a cruiser then it should be plenty strong. This would allow you to use a 1:1 transmission. You'd be going way over highway speed with 2.73's at 2400 RPM. Something like the Allison 545 4 speed automatic I mentioned earlier would fit the bill really well. You can usually get them real cheap, because they came in a lot of school buses. You would probably have to use a divorced style transfer case with it though.

[cayoterun]

YeeHaw: Found 14"clutch disc&pressure plate on Ebay from a 50s-60s Mack gasoline motor in top condition that fits "Balaur". Received it today so the search for an overdrive tranny is now on.
The small flywheel/flywheel housing I have now is the same as the standard clutch setup used on 478 V6 powered GMC trucks. If anyone knows of a tranny, I'd sure appreciate any leads.
Thanks,
Cayoterun