Replacing seal in gearbox

[bulldog69]

Dave: I get your point on the corn head grease, and I guess in this application I'll retract my suggestion. In a 20 year old PHD, I stand by the idea and have no plans to pull the gear box apart. But in a much newer brush hog... better get the seal.

I thought it was a good option myself. Don't know what's wrong with a "old farmer trick" in the first place. I know of several gear boxes that have grease in them and run just fine. My PHD is one of them to and my old JD tedder actually runs grease instead of oil.

 

[AlbertC]

Not a hard job because you are not afraid of damaging the old seal.

Buy a new seal first, made for your model. Later you can switch to lower priced seals but for the first time you want one that is exact.

From that new seal you can take measurements or go to a bearing supply place and have them find an equivalent seal for the next time.

Post a couple of photos. I expect a flat screw driver and a hammer will enable to to get the seal out of its recess.

In my experience, it is wise to use gear oils with extreme pressure additives. Most auto parts places have such products as they are required in differential axle gears.

The EP additive increases the cost very slightly.

The "fill it with grease", is certainly an old farmer's trick. Wonder why, if it is such a good idea, gearbox manufacturers like COMER do not use grease.

Before condemning the seal, make certain the gear box has not been over filled and check carefully to see if a tiny vent is present and if so open.

Rainwater getting in to the gearbox will raise fluid levels and cause over pressures and leaks. Outside storage is best avoided for long life.

Is the pto shaft the correct length? Too long and extreme pressures happen when the hog is raised at the point where the pto shaft is horizontal.

Youtube has many videos on pto shafts.

Dave M7040

Well I cleaned the vent with mineral spirits and blew it out with my air compressor. I don't believe it was stopped up. Then I cleaned up the gearbox and frame so that I could tell if it was leaking and I cut about 45 minutes and when finished it was still leaking.

I wonder if it would be worthwhile to drain the oil and refill to make sure that it didn'thave too much oil in it. When you refill do you just make sure it is good and level and then fill with oil until it begins to drip from the plug in the side?

This is the first time I have added oil. I don't know if it had too much oil in it from the factory but I just now noticed it leaking.

 

[M5farms]

Should have a lower plug and upper plug fill till it runs out bottom plug

 

[JRobyn]

I'm pretty sure my BH286 just has a single fill/check plug.

 

[Fallon]

There's another option: I have an old post hole auger that was leaking from the same spot. I replaced the oil with Corn Head Grease. It's thick enough that it stays put, but coats the gears well when they get moving. No leaks!

I did the same thing for my flail mower. Paid $100 for the mower. Had $400-500 into it total when the seals started oozing. New seals were gonna run me $70 or so for the ancient beat up machine. Grease worked fine for several seasons (have a new flail for this season). I'm sure oil lubes better, but even with sub-par lube that gearbox will outlast the rest of the flail.

Probably best to replace the seals on a nicer newer machine though.

One thing to consider is why the seals blew. Bad bearings can cause good seals to go. Replacing the seals in that case is a temporary fix at best. Make sure there is no play in the shafts before replacing the seals.

 

[Dave M7040]

One thing not mentioned so far is the proper fitting of the pto shaft.

Too long and it will put great forces on both the tractor and implement as the implement is raised to the point where the pto shaft is horizontal if the shaft bottoms out.
This is a typical gear box. I think the seal will come out without taking the bolt on plate off.

Dave M7040

 

[Dave M7040]

I thought it was a good option myself. Don't know what's wrong with a "old farmer trick" in the first place. I know of several gear boxes that have grease in them and run just fine. My PHD is one of them to and my old JD tedder actually runs grease instead of oil.

And front mounted snow blowers' gear box.

The fact that this one is broken is not my point, rather to just show it is lubed in grease.

There are many different types of gear boxes. Like the broken one, a worm gear style with one of the gears brass.

The type and specifications for the needed lube arise from the calculations of the pressures the teeth are exerting on each other.

If you have a gear box whose design generates high face pressures, then the lubricant becomes important hence the development of extreme pressure additives for some gear oils.

My point, probably using poorly chosen words, is that the same solution is not appropriate everywhere.

Dave M7040

 

[gator]

If I were you I would go to THIS LINK for the parts manual and compare your gear box to one of the multiple used on this model and see what is involved in replacing the leaking seal.

 

[TheMadOne]

A good trick for a stubborn seal is to use a screw or two on the old seal. Run them in enough to bite into the seal material and then use them as fingers to pry/pull against. In most gearboxes it should pop right out. Then like was said above, oil the new seal, clean the shaft thoroughly, and slide it on, using light blows to seat it.

Make sure to go slow on the screws to not dump metal shavings into the gearbox. You want to tear/puncture the metal, not mill pieces off.

 

[Dave M7040]

This exploded parts view from the Bush Hog site shows the risks in removing the bolt on end plates.

Unless you really know what you are doing and have the machinist tools to take measurements, most people don't realize there are gaskets acting as needed shims to control how the gears mesh.

When the gearbox is set up at the factory, one of three thicknesses of gaskets will be selected for the pto shaft end and the cutter end.

See parts I have marked in red. Each a different thickness..

The correct thickness must be used or the gearbox life will be seriously shortened.

Dave M7040