changing really old gearbox oil

[coffeeman]

I recently purchased an old bush hog rotary 10' cutter - 3 gearboxes.

The gear oil looks really nasty, so I would like to do a 'flush' if possible or practical.

So far, I have suctioned the oil out using a suction pump can from Northern Tool. Works OK, but the oil is really thick - took about an hour for each gearbox to empty.

Now what I am thinking about doing is to add some 30 weight oil to each gear box, then run the cutter for about a minute, then suction again and maybe repeat until I get the gunk out.

Then finally add the gear oil.

This is similar to what you can do with a really dirty crankcase.

Does this make sense or am I making things way too complex?

DJ

One of the first cars I owned had a lot of miles. But, ran good. Of course at 16 I cleaned it up and decided I should clean out that old engine. They sold some kind of engine cleaner back then. Cleaned it real good. Filled it with new clean oil and the engine started knocking. Since then: if it ain't broke don't fix it.

Cheers Coffeeman

 

[IslandTractor]

If I were to go the motor oil route I would heat the bulk oil up first. Get an old metal pot from the kitchen and set it on the BBQ grill for a while. When it starts to have wisps of vapor coming off of it it's ready. You don't want it boiling as they may hurt the seals. Add the hot oil to the gearbox and run it for a minute or two. The hot oil would thin out the old gunky gear oil and let you siphon it out. In the end whatever residue left in there would be a lubricant. Not true with a flush with Diesel fuel. I used to flush engines with kerosene but I was always leery of having solvents in the engine. The hot oil does wonders.

Why not just run the mower until the gearbox warms up? Check it by touching every five minutes or so while mowing. It shouldn't take long especially if you are in thick vegetation.

 

[Heavyduty]

On these old bushhog its a good idea to run the johndeere cornhead #0 grease. If your bushhog is like mine, it has been used to cut down little trees while being pulled to fast and hitting every scrap metal/concrete I could find. If you find that it wont hold the 90w, you can change out the seal or you can put the #0 in. I went the cheap/easy route. If I had a fairly new mower I would repair it the proper way. Also the #0 grease sticks to the gears better to protect them from rust while storing over winter.

 

[Soundguy]

I dump in diesel in mine, agitate a lil...then drain...

soundguy

 

[thartweger]

Mind you I have very limited experiencew ith these things, but it seems all the gearboxes ive messed with (most which are used in very dusty dirty climates i.e. bush hogging) the gear oil gets nasty very quickly. I dont know that dirt being in there will hurt anything, but it hasnt effected what I do. I just ad to it when it needs it. I also havent used many different bush hogs either, just a couple, and they are dinosaurs, but the disgusting looking gear oil hasnt effected their performance. After mowing down a 20 acre field or so Ill drain it and refill it though as these guys have mentioned, I used diesel.

****, I've used diesel to flush out oil in engines. Just let it sit, drain, and evaporate before refilling.

 

[Soundguy]

Most of that disgusting looking oil is just a little water emulsion. since the gearbox generally has a very tiny preather plug with dirt cap. not much real 'dirt' can get in there.

soundguy

 

[SPYDERLK]

Most of that disgusting looking oil is just a little water emulsion. since the gearbox generally has a very tiny preather plug with dirt cap. not much real 'dirt' can get in there.

soundguy

Especially since while your stirring up dirt the gearbox is warming.
larry