The Stovebolt Site Forums The Shop Area Driveline Mystery Gearbox

I was at the "local" Truck yard looking for spicer boxes, when I came upon a cab on chassis with this strange gearbox on it. The brake drum was aft on the truck, with a speedo cable and an eaton electric motor. One drive shaft in and one shaft back out. Is this some in-line pto assembly I never heard of? I couldn't see any tags or casting marks.

https://drive.google.com/drive/folders/1JacWNIsx23C2fDgkOUWayt2Po80_2bNO?usp=share_link

Is the unit in the main driveline between the transmission and the rear axle? It looks like some type of electric shift over/under box that allows the driver to split each main transmission gear. It's the same principle as a 2 speed rear end, just divorced from the rear axle. I've seen similar boxes with manual shift, but never one that's electric.
Jerry

Yes, looks like it replaced the midpoint bearing and carrier. Do you know offhand what make the box is? I want to see if there is any info out there about them.

If the motor is Eaton, chances are the gearbox is, also. Unless you can find a tag with a model number somewhere, finding any information on it might be difficult. I used to drive an old 3-axle Freightliner with a 270 HP Caterpillar 1674 engine, a 5 speed transmission, and a "3 speed" Eaton rear end. The thing was actually two 2-speed rear ends in tandem, and the "intermediate" speed was obtained by shifting one axle to low and the other to high ratio, and letting the inter-axle differential split the difference in the gear ratios. It was also electric shift.
Jerry

Sounds like I'll need to make another trip then. Thank you for the help.

Most of the 2-speed auxiliary transmissions are underdrive/direct ratio. They allow an extra gear reduction to each main transmission shift, effectively splitting each gear before making the next upshift. It's a good way of keeping a heavy load moving without dropping the engine RPM out of the effective power band between shifts. That type of transmission doesn't do anything for top road speed- - - -it just keeps the engine it its optimum power band more of the time. A 3 speed auxiliary also includes an "overdrive" ratio for each main transmission gear. Older Diesels, especially Detroits, needed all the gears they could get, since the usable power band was only 400 RPM, like 1750 to 2150.
Jerry