Rotary mower leaking gear box.

Rick Remmert · Oct 6, 2016

I was getting tired of adding oil to my 5' rotary mower gear box that had a bottom seal leaking. I was adding almost a quart of 140w gear oil each time I would use it. When I clean the deck after mowing, I noticed how warm the gear box is. I mow with a Super C in weeds and grass that are 3' to 4' tall. Sometimes for 5 to 6 hours in 100+ heat. I marked the 1/2" pipe plug used to fill the box on the wrench flat that was pointed down. From the bottom I drill a 1/4" hole as deep as I could without breaking out the top. Turned it on it's side a drilled a 3/32" hole on the marked wrench deep enough to break into the 1/4". Now I have a vent plug. Now when I add oil, it is only 5 or 6 table spoons full. Lot easier than tearing the bottom off the mower to get at the bottom seal. I sure didn't have anything to loose.

Texasmark1 · Oct 6, 2016

New mowers now come with vented fill plugs to prevent just what you are reporting. To supplement what you did, rather than add more oil, add #2 grease. Eventually your leak should stop.

MF#1 · Oct 6, 2016

Yep, I have an 80's Bush Hog brand 307 that's been getting grease since 2000. It will probably outlast me.
It came with a hole pre-drilled in the plug at a diagonal instead of a right angle, yours should be fine.

wellmax99 · Oct 8, 2016

Alemite? 321620 Breather; 1/8" PTF
Item # 901-198388ORS? Model # 321620

might look into buying one of these little fellows.
gearbox breather cap, must have some type material in vent hole to keep moisture from entering gearbox if its rained on.

also if the gearbox is now leaking, many add john deere or caseIH corn head grease to old gearboxes: it is one of the best lubes about and will not run out near as fast as regular gear oil

if the leak gets too bad then fill it with regular grease, many old gear boxes have ran for years filled with gear grease.

Ragnarok · Oct 8, 2016

My old JD grooming mower has some brand obsolete gearbox...vented fill-plug and the bearings are tight...however it leaked bad out the bottom shaft.

I didn't even drain the old GL5 oil out and just filled it slightly over-full of JD corn head grease.....Will spew a bit of grease from the top-vent...but I've not had to add any oil/grease in three years!

Rotary mower leaking gear box.

Rick Remmert

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Texasmark1

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MF#1

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wellmax99

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Ragnarok

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