What is Side Mount Rotary Cutter Gearbox and Why Do We Use Them?

A simple gearbox that is splash lubed wont care much as long as the fluid level is appropriate. It may take more oil in one direction than another depending on the shape of the case. Anything with an actual pump you have to be much more careful, but that doesn't apply here. Keep in mind too much oil will generally cause the oil to run hotter, not cooler. You just need enough that it is actually touching a spinning gear and getting splashed around.

Now a differential on a car/truck is a different beast because you SHOULD be able to drive those things basically nonstop forever with hundreds of HP going across it and proper lube is critical to that, but even though it's not what we're talking about here Gale Banks has posted a series of really interesting videos on youtube about what his company went through to test and design a differential cover in a way that did not degrade lubrication inside the differential. Easier said than done..

I imagine that on most you could “extend” the vent plug with a threaded elbow and some pipe fittings so the vent stays on “top” .

I suspect that the vent plug needs to be generally connected to the air space in the gear box. If you flip the gear box upside down and just make it so the vent plug is extended to be on top, oil could dribble out any time heat increased because the base of this new vent tube would be full of oil and an increase in pressure in the gear chamber would shove more oil into it; if the tube is long enough to expand without dribbling it would merely be a weak liability (catching stuff on it and breaking off the vent tube and/or threads at the gear box) instead of a constant mess.

So I have a Woods MD160-1 60" rotary mower (made in the year ) with a destroyed gearbox; it is not serviceable. I can get a new Woods gearbox for it but they are quite expensive, about $ as priced from two different suppliers. So I am looking for other options.

This Woods gearbox is unusual in that it is a side mount. There are two plates that extend up vertically from the deck and the gearbox bolts to that. Here is a picture of the gearbox. You can see how there are four large bolts, one at each of the four corners of the gearbox, that attach it to the vertical plates. The plates are 6" apart, or put another way the gearbox is 6" wide.



All of the generic rotary mower/cutter/shredder gearboxes I have seen are all bottom mount in that they bolt directly to the deck. All of the new rotary mowers I have seen all use the same bottom-mount gearbox style with varying degrees of HP rating and different sizes and styles of input and output shafts.

Is anyone aware of a source that supplies generic side mount rotary mower gearboxes? I have looked for hours and all I see are the bottom mount style, at least for single spindle rotary mowers where the output shaft directly attaches to the stump jumper. I found at least one side mount out there at agrisupply but it is for a multi-spindle mower; the ratio is wrong and the output shaft is far too small.
Gearbox 1-3/8" 6 Spl Input | Agri Supply

I want to be sure I have not missed another option before I give up on this unit or convert it to use a bottom-style gearbox. That will take some work, and about $400-$500 in parts. I will not only need the gearbox, but will need a new stump jumper (Woods output shaft is a smooth 1.5" shaft with a keyway), new blades, and possibly a new PTO shaft assy, or at least a new output yoke. That's another story.

Thanks in advance