Rotary Cutter Gearbox HOT???

N80 · Sep 12, 2013

I had posted years ago that my fluid is always very milky looking and somewhat foamy after use. It does not get water in it. I have opened the box and thoroughly cleaned it with kerosene and put new, quality fluid in it. I fill it to the proper level and yet after just a few uses the gear oil is a milky light brown and pretty much stays that way. I've given up worrying about it since it is still working normally. It does not get used daily, or even weekly but there are days in the spring and summer where I'll run it for 4-6 hours. No problems at all.

Soundguy · Sep 12, 2013

yep.. them gear boxes can be hot.

as others said.

get a vented cap.. and run good clean gear oil or whatever lube it calls for in em.. and do not over or underfill.

greg_g · Sep 12, 2013

N80 - working normally is subjective. Wet fluid necessarily causes the tranny to run hot. I suspect you're a victim of two things. First, remember that the gear box is typically only 1/2 full of gear lube. Without a good kerosene flush, you're pouring clean oil into a filthy sump. Yes, you mentioned kero. But do you do it EVERY time you drain brown milky fluid? And do you take steps to mark sure the kero washes above normal fluid level?

Second, transmissions left outdoors to the elements are subject to internal condensation. That's likely where your water comes from in the first place. Oil + water + agitation (mowing) = dirty thin and foamy gear oil. Do you to don't you have a vented fill plug?

A vented fill plug wont eliminate condensation completely, but it does provide an escape route for some of the moisture. Add a good kero wash between oil changes - and your tranny is almost guaranteed to run cooler

//greg//

N80 · Sep 12, 2013

Thanks Greg. This is a real simple gearbox. Just a box with two gears in it. Top comes all the way off. So I pulled the top off, sucked and dabbed all the old gear oil out. No rust. No dirt. No goo. Spray it with kerosene. Wipe it all out. Fill it with kerosene, put top back on and run it for a few seconds. Get all the kerosene out. Top back on. Fill it with new stuff. Clean vent valve (which is separate from fill plug and sits on top) and go. Two or three uses later and gear oil is milky brown again.

But, I've only done that once.

Anyway, always works normally....whatever that means. No noise, vibration, or excessive heat. Never any visible metal in the gear oil.

I think you could be right about condensation. Not sure I can do anything about it. And I get the impression at its current rate of use, and from the clean appearance of the gears even now, it will last longer than me.

Soundguy · Sep 12, 2013

one other thing.

some vented fill p[lugs use a ball and spring, some use a loose cap.

hard rain can intrude ont he loose cap style.

a bucket turned over the gearbox will solve that.

lastly.. you can buy a lil transtune seafoam and add an ounce of it to the gear oil. it's rated safe for trannies and hyds and should be fine in a gearbox.. it will disolve water and help it flash off with use, faster..

if yer cheap.. 90% rubbing alcohol will work too.

N80 · Sep 12, 2013

My JD vent has the ball and spring type. If functions but a little oil gets through it. Not much, but enough to cause dust to stick around it. I already keep a bucket over the gear box even though the cutter is in a shed now. I may put some Seafoam in there. Can't hurt.

P.S.: I am cheap. Tight as a tick is what my Dad used to say.:laughing: