A twin screw is a tandem win which both axles are drive axles. Most tandems in the 50's and 60's had only one drive axle and the other was like a trailer axle. Eaton had a really crazy setup for a twin screw in the 50's in which the interaxle drive shaft went over the front axle. It was short lived and replaced with a through shaft similar to what Rockwell used. The Eaton setups are very rare. Not many were built and few of them survived It looks like this one may be a one or two year only three speed axle that used the old interaxle over the forward drive and shifted manually. By the early 60's Eaton used a thruoughshaft type power divider and the three speed Eaton became quite popular. By the 60's, the three speeds were shifted with air. My first Diesel truck had a 3 speed Eaton. The setup is comprised of two two speed Eaton Axles. In low range, both axles were in low range. In high range both axles are in high range Intermediate range is achieved by having one axle in high range and the other in low range. The power divider splits the ratio. The power divider uses a sun gear with planetary gears and power dividers were a very high maintenance item with 3 speed axles. I got my commercial drivers license in 1959 and still own a fleet of trucks. I have never actually seen a manual shift 3 speed Eaton. If it were in my neighborhood, I would buy it just because it is so rare. However, it will be very difficult finding parts for the Eaton. There is nothing different about the 2 speed and 3 speed Eaton except for the shifter setup. With a 3 speed Eaton behind a 5 speed a truck had 15 very evenly spaced gears. The drawback was the maintenance.
Thx for the info. Does anyone know what rims are on this truck? I hope it's safe to pump up the tires without blowing up. Lol Hopefully I can pick it up. I just want it. Would anyone know how many where built and how many are still out there. Has anyone ever built a box for these trucks??
Cren, Was the Eaton which you describe at all similar to the Detroit-Timken model SBD1555? I have one in a 53 White which has sat for many decades and I haven't had running. It looks to have a pass through drive shaft to the rear axle and it has a power divider, altho not sure if it's a two speed or 3 speed divider. Smangy, I wouldn't air up too many tires....leave well enough alone as long as the truck can be dragged/rolled onto the transport vehicle. Those old tube tires could blow if you change their status quo (such as putting air into them or driving more than a few miles on them)! It's possible that they are tubeless, as both were used in the late 50s, but be cautious about airing up any large truck tire which is flat or low on air.... I once (slowly, on a very rural road) drove a tandem axle truck with tube tires which had been sitting for many years....by the time I drove 10 miles, three of the ten had blown. Also, when you do air them up, make sure you use a remote clamp-on type air chuck....in other words, don't be standing or kneeling next to the wheel.
I'm kinda nervous. I only have seen the truck in pictures. Cant imagine how big this thing is. Today I pulled beside a semi truck in traffic and looked over at the wheels. Wiw 22.5 they are huge. Lol I got it for $1000, not much lost if I wanna resell it .
Detroit Timken made a 2 speed axle, but I'm not sure if they ever made a 2 speed tandem. Here is a diagram of Eaton vs. Timken tandem units. The Timken which later bacame Rockwell and now is Meritor used a through shaft. The 1950's Eaton had the interaxle driveshaft above the forward axle. This design didn't last very long. In about 1960 Eaton went the through shaft design that is the standard of the industry today.
As for the tires, the wheel I see on the drive shaft is a lock ring style that is relatively safe. It is still produced today. On the drive axle, the lock ring are on the inside and couldn't go anywhere even if a lock ring were to blow off. You have to be more careful with the steer tires. The lock ring is to the outside. If it is not properly seated, it can be dangerous. I run all tubeless tires on my fleet and have been for over 40 years. But I have been messing with tube tires for over 60 years. Here is a photo of my latest toy. I put just enough air in the steer tires that they stood up and then towed the thing 70 miles per hour in 100 degree weather. Unless the tires have been totally flat for years, bias tires are less likely to blow than radials. It was running them so slick that they wore down to the tube or running over a sharp rock that caused the old bias tires to blow.
Cren, I see the differences in the tandems....quite different actually. Somewhere I have some lit on the Detroit tandems, and will post pix if I locate it. Good luck getting it home, Smangy!
Thx for all the info Found all this on the web about the rear axle.
The Chevrolet Walking Beam/Power Divider setup was made for GM/Chevrolet by Truck Equipment Company starting in 1956. Prior to 1956 Chevrolet Tandems were dealer/owner installed from third party vendors. I'm not sure if GMC used the same set up or not...
On the bigger trucks Chev and GMC diverged quite a bit. It wasn't just GMC engines and different badges like on the medium duty trucks. Maybe I'm commenting on the obvious here but be careful about assuming what you find in the Chevrolet book applies to GMC. Then there is the confusion over what was produced for the Canadian market. I cannot speak to that as I have only worked on US GMCs and Chevs. The three-speed power divider is a new one on me and that alone might make the truck worth restoring or at least preserving.
You might also look up the ATHS (American Truck Historical Society). Their members mostly focus on heavy trucks, like what is now yours, and heavier. They have chapters all over the country and regional shows and a national show annually. I've been to seeral nationals and they had upwards of a thousand entries. The National in Yakima WA attracted lots of logging equipment from B.C. Jim Carter was there and I talked to him at length. Nice guy. They skipped this year but a couple of the regional shows went on.
1951 3800 1-ton "Earning its keep from the get-go" In the DITY Gallery 1962 261 (w/cam, Fenton headers, 2 carbs, MSD ign.), SM420 & Brown-Lipe 6231A 3spd aux. trans, stock axles & brakes. Owned since 1971.
I'm so excited and kinda scared. It's being delivered saturday morning. Dont know what to expect. Hope it's all good. Will post better pics and video when I get it parked.
Shes a beast! Cool truck. looking forward to more pics when it gets to you.
~ Billy Old Dominion Stovebolt Society: Exotic Animal Division 1946 Chevrolet Cab Over Engine | In the Gallery | Video | More pictures 1959 GMC 860 | Pictures 1950 GMC 450 FlatbedW/W, Air Brake equipt (25% Owner) | Pictures 1950 Chevrolet 3800 | Pictures I've got a trailer and I'm not afraid to use it!
You got 348 engine with Power Steering...looks very un-molested and original. The Power Divider is Low-Low, Low and Direct...should pull a mountain down in Low-Low and Granny...
You also have Dayton Rims, NOT Firestone RH-5's, so you're good to go! Any big truck tire shop will hook you up with new rubber when the time comes!
Sweet on the rims. I was scared that I got the widow maker rims. The truck all created up is not for me. The driver parked the trailer at my house fully loaded. He had to go do another run. Will unload later this week. The truck will go into storage until I finish my other projects. Too many toys. This truck sitting on the trailer get lots of looks and everyone stops and asks what it is. Lol like a celebrity. The truck itself needs lots of work. The rear tandem axles look good but the walking beam design looks a bit rough. Will need a rebuild. The front end looks good and solid. The tires are shot. The body needs lots of attention. The engine has oil and the plugs look good. Gona power up to see if I can turn over. The rad is empty and so is the power steering pump. The tranny shifts nice and the clutch pedal moves nice. The brake pedal was seized, but with lots of foot power I got it to move. Now it goes to the floor. Maybe the booster needs a rebuild??? This is gonna be a bigger project than I though, but she is a keeper. Love it and so does my wife. Plan on keeping it all original as long everthing works . The rear walking beam may have to go. We will see. Thx everyone for all the help. Steve
Make sure you take your time and not get in a hurry when trying to wake up the engine after a long nap. There's a Tech Tip on steps to take that can help you through it...doing it wrong can break things and end up costing lots of extra money to fix.
I'm looking forward to following along on your adventure with this truck!
Finally got it unloaded. I got the chance to drive it while being pulled. Felt exciting. Lol It wont be till next year after the snow melts before any work will start on it.
Quick question for u all smart people. How do I tell if this is a 348 or a 409. Been told to look at the dipstick location by others, but is there any other way. Been reading a lot about this truck online and in books. They where correct on some stuff and wrong on others. Like my rims are not 22.5" like it says in the specs, its 20". Is there like an owners shop manual for these big trucks??
You will be able to get 22.5 tubeless rims that will fit on those hubs easily. That's what I did for my 860. I think I only paid about $100.00 each but that was a few years ago. Keep an eye for a manual on Ebay. I found my rims there too. It will be exciting to see the progress on the truck once you start.
~ Billy Old Dominion Stovebolt Society: Exotic Animal Division 1946 Chevrolet Cab Over Engine | In the Gallery | Video | More pictures 1959 GMC 860 | Pictures 1950 GMC 450 FlatbedW/W, Air Brake equipt (25% Owner) | Pictures 1950 Chevrolet 3800 | Pictures I've got a trailer and I'm not afraid to use it!
