I have an MTD lawn tractor 12.5 hp 38" deck. I bought it new ($820 at walmart) in april 2000. I have mowed about 1 - 1.25 acres from may to october since april 2000. This year I have let some areas go wild so I'm down to perhaps 1 acre.

In mid june of this year when cleaning the grass out of the differential area I got grease on my hand. I removed the wheel and on the left side (as you sit on the mower) there's a small indent about 1/2 way up the diff and that's where the grease is coming from. This diff is a sealed unit, packed at the factory and no way to add grease. I get about 1/4 - 1/2 teaspoon of grease that leaks out every time I mow (every 7 days) - when it sits not being used it does not leak. The grease is like grease gun grease not gear oil. Eventually the diff will run dry and seize up.

I cut off the back panel to gain access to the diff. I want to drill a hole in the diff to add more grease. I want to approximate what I get on my hand, perhaps a thick mix of 80-90 gear oil and grease gun grease, something that is lighter than the grease but not runny.

My question is has anyone ever opened one of these diffs? What clearance is there from the inside of the diff housing to the gears? Where can I drill the hole so I don't hit anything (where's the most clearance?) and have room inside the diff housing to plug the fill hole with a small rubber stopper? I suspect the clearance inside the diff is minimum. Do I have 1/2" from housing to gears? That would be fine to hold the rubber stopper. I suppose I could use some sealer like permatex (I'd discuss with the auto parts store what they'd recommend) and dig it out with a paper clip but a stopper would be easier.

Thanks,

Tom