Hi all, about every 5 years I'm on here hoping someone's found a tandem (twin screw) Chevy tractor unit from the mid 50's since all my looking of craigslist and farm auctions has turned up nothing. So has anyone who's been searching had any joy?

You're in luck...Stovebolt member named 'BHMOTOMACH' in Charlotte, NC has an original mint condition 1956 Chevrolet twin screw tractor, even has a few pictures in some of his posts. Look him up!

James

See that a '57 tandem turned up late last year on craigslist and someone posted it on here. Did anyone go and have a look at it?

I think most of the twin screw rigs were conversions by aftermarket truck builders. I'm not sure when Chevy started offering factory-built dual drive rigs- - - -most of them had a non-driving "tag axle" if they needed an extra set of wheels for load-carrying capacity. I've seen a few pretty good adaptations of military twin screw rear ends. One I saw in a wrecking yard had a torque splitter and two driveshafts, not the conventional inter-axle differential. It was under a late 40's truck, either a 2-ton or maybe bigger.
Jerry

Hy Guys, I believe that Chevy started offering factory tandems in 1956. They used a "power divider" behind the transmission, and two driveshafts from there back to the diffs. They mounted a pillow block on the forward diff which held the driveshaft to the rear diff in place, The two diffs were identical, and were the heaviest "corporate" diffs", not Eatons or Timkens. As to the tandem that showed up here last year, I bought it, it was in Oregon, and was an 8700 series.

I believe 1956 was the first year Chevrolet had the twin screw tandem. The early tandems used a conventional 5 speed trans. followed by a combination auxiliary-power-divider type transmission with two rear drive shaft outputs. One drive shaft went to the front differential and the other went to the rear diff. It was quite complicated with several u-joints and many grease points involved. By 1960 Chevrolet had gone to the tandem setup that is now used, single driveline from back of the transmission through the power divider mounted in the front differential, short drive shaft between the rears and into the rear diff.

Jerry is right about most early tandems being a dead 'tag axle' type setup. Extra axles afforded more load capacity.

James

The truck belongs to my Dad. He keeps it in Arizona. He spent a considerable amount of time and researching and restoring the 1956 Tandem. His efforts turned out fantastic. The truck was factory built and the tandem axles are "Genuine Chevrolet" as is the Allison 6 speed automatic tranny.

Here is a link to the an interesting thread about the very thing you guys are talking about, with pictures!!! Very cool truck too.

http://forums.aths.org/InstantForum414/Topic65918-4-1.aspx?DisplayMode=1

Bhmotomach, that is a beautiful truck! You seldom see trucks of that vintage and that one looks perfect!

That is a fabulous truck indeed and I think it is in the Big Chev Trucks book I have. Still amazes me that it's the only one out there, I'd have more chance stumbling upon a parked up Big Tank Corvette or a COPO Camaro than a tandem with air and 348 big Chev truck.