Bush Hog Gear Box Leaks

[WoodieSC]

I've got a Bush Hog 'Squealer' 5' bush hog. I rebuilt the gear box last year and everything 'looked good' as it went back together, and 'felt' top notch when I started it up. It's probably only got maybe 10-15 hours of running time on it since then, but I noted this weekend that there was some lube oil leakage on the dirt where I park it.

I checked the lube level and it was down a couple of inches (to right at the bottom of the top gear section) and the 'stump jumper' pan was coated in oil. The bottom seal lasted 18 years before it went bad last time, and this one is now leaking after a few hours usage. I know the shaft looked real good or I would have sleeved it or replaced it, so I can't imagine what's caused it to start leaking so quickly. My mechanical engineer neighbor, who knows gear boxes inside and out, said everything looked 'near perfect' to him before I closed it up last Fall.

Before I pull things apart to replace that bottom seal again, I thought I'd try some John Deere Special-Purpose Corn Head Gun Grease - AN102562, which is apparently rated NLGI - grade O grease.

Has anyone used this grease before in a higher speed gear box like a rotary cutter? If so, what's been your experience?

I'm going to be careful here because this is a $600 gear box and the vertical shaft/gear head itself runs $160. Just checking that this 'Corn Head' grease is a good solution since the 90W gear oil sure isn't staying on the right side of the seal.

Thanks.

[Bownut]

Is it vented? If not it will could up pressure and push it out, especially if over filled.

[WoodieSC]

Is it vented? If not it will could up pressure and push it out, especially if over filled.

When I filled it I made sure it was measured to be at 2 3/4" below the top edge (or whatever the manual calls for).

I checked the vent plug today at lunch when I realized I might have missed that 'fun fact' and had my fingers crossed for luck. I did find it to be dirty, but then removed the top plate and found that about a quart of 90W that I'd put in on Sunday afternoon had already leaked out this week while sitting untouched. So if the vent plug did cause the initial leakage it must have really done some damage to the seal, which I tend to doubt, or something else did the dirty deed.

I'm thinking I'll try the 'Corn Head' grease and see how it looks from there and plan to pull the bottom off as soon as I can find the time to do it.

I just hadn't expected to have to tackle this again so soon.

[Bownut]

Could be a bad seal and shafts can "look" good to our eyes and still be bent or out of round, or have a groove in it. Check the bearing real good, if there is play, it will leak. It's cheaper that you found it now instead of burning it up.

[baldpate]

Fill it with corn header grease and go. I've been using this trick for years on all types of gear boxes from bush hogs to combines. Check it periodically but you shouldn't have to add any for a long time unless its run a lot. With a bad leak on a high speed box, I may only go through 3 tubes in 100 hrs operating time.

[WoodieSC]

Could be a bad seal and shafts can "look" good to our eyes and still be bent or out of round, or have a groove in it. Check the bearing real good, if there is play, it will leak. It's cheaper that you found it now instead of burning it up.

Great points. Thinking back I don't know why I didn't think to check the 'run out' on the shaft since I've got a dial indicator downstairs. But neither myself or my engineer neighbor thought there were any areas of the shaft that should cause any problem with a bearing or a seal.

I'm beginning to think I may have damaged it two weeks ago when I grounded the hog out on the edge of a ditch that proved to be narrower and deeper than I'd remembered it to be. The hog got stuck as did my rear tires and had to work myself out of the ditch using the bucket, etc.

I'll raise the unit up this weekend and see if there's any play showing in the blade bar, etc, indicating possible damage to the bottom bearing. Because like you said, it's cheaper to do it now than burn/tear things up. I came close last time when I didn't realize it had gone dry on me.

Fill it with corn header grease and go. I've been using this trick for years on all types of gear boxes from bush hogs to combines. Check it periodically but you shouldn't have to add any for a long time unless its run a lot. With a bad leak on a high speed box, I may only go through 3 tubes in 100 hrs operating time.

That's good to hear baldplate. I'm going to pick some up and try it out after I check it over for excess play. If the spindle is moving around I just might have to pull thing apart again.

[Fireman]

We've been pumping ours full of that grease for years. We've rebuilt it several times but just seams we can never get it to seal. They take a beating and the rebuild kits just don't seem to be O.E. spec

[WoodieSC]

We've been pumping ours full of that grease for years. We've rebuilt it several times but just seams we can never get it to seal. They take a beating and the rebuild kits just don't seem to be O.E. spec

Interesting.

If I have to do it again, I wonder if it would be worth having the main shaft chromed (or nickel-ed?) and re-machined back to spec diameter just to make sure there isn't a worn or corroded section that looks good to the eye but really isn't....??? If that would work it would sure be cheaper than a new shaft/gear head at $160+ since I can get the machining done for free.

I've definitely not babied this bush hog over the past 20 years. I've rebuilt the housing a few times and it's 1/4" plate around the sides now. Just need to keep her going because the budget isn't there to replace it anytime soon!

Thanks for all the info, guys.

[WoodieSC]

Does anyone know if there's any compatibility concerns with the Corn Head grease and the 80W-90 gear lube that's in the box now? Other than dilution, I'd expect I'm OK with anything I'm unable to remove from the low side of the gear box, although I'm thinking if I can pressurize it from the top with an air compressor I might be able to 'blow out' what's in there right now and try to catch it underneath.

Comments, suggestions?

Thanks.

Btw, my neighbor says these low end gear box replacement seals are often manufactured with upwards of a .035" tolerance vs. the ones for the high end gear boxes are down at .001"-.002" like the bearings. If that's the case, it's no wonder the replacement seals tend to leak!

[smitch320]

Does anyone know if there's any compatibility concerns with the Corn Head grease and the 80W-90 gear lube that's in the box now? Other than dilution, I'd expect I'm OK with anything I'm unable to remove from the low side of the gear box, although I'm thinking if I can pressurize it from the top with an air compressor I might be able to 'blow out' what's in there right now and try to catch it underneath.

Comments, suggestions?

Thanks.

Btw, my neighbor says these low end gear box replacement seals are often manufactured with upwards of a .035" tolerance vs. the ones for the high end gear boxes are down at .001"-.002" like the bearings. If that's the case, it's no wonder the replacement seals tend to leak!

I've heard of people mixing 90w with the Corn Head, but am I not certain.

[papagood]

Are you sure it's leaking from a seal? Just to be sure, drain the oil and put a hose with around 5 psi of air pressure (too much pressure could blow your seals out) on the vent plug. Spray the seals and oil plugs with soapy water and look for bubbles.

I work in a plant that makes gearboxes and this is how we test for oil leaks.

[baldpate]

It doesn't hurt to mix it. Don't over think this. When you replaced the seal it just didn't seat quite like it should. Corn head grease is good, I promise. I've got gear boxes that have mowed upwards of a thousand acres with a bad seal. It's easy, fairly cheap and doesn't stink like 90w does! When your gear box finally tears up them you can start fresh.

[WoodieSC]

Are you sure it's leaking from a seal? Just to be sure, drain the oil and put a hose with around 5 psi of air pressure (too much pressure could blow your seals out) on the vent plug. Spray the seals and oil plugs with soapy water and look for bubbles.

I work in a plant that makes gearboxes and this is how we test for oil leaks.

The only place it could be leaking is out the bottom as there are no seams or openings below the highest oil level other than the bottom half of the horizontal drive shaft, which isn't showing any leakage.

It doesn't hurt to mix it. Don't over think this. When you replaced the seal it just didn't seat quite like it should. Corn head grease is good, I promise. I've got gear boxes that have mowed upwards of a thousand acres with a bad seal. It's easy, fairly cheap and doesn't stink like 90w does! When your gear box finally tears up them you can start fresh.

LOL... the price of gear boxes I have no intention of allowing it to tear itself up if I can help it.

I'm going to try to suck/siphon out as much of the 90W as possible just to reduce the dilution of the CH grease, but will then fill her up and take it for a spin to see what happens.

Will let you know in case it helps anyone else in the future.

Thanks.

[WoodieSC]

I'm going to try to suck/siphon out as much of the 90W as possible just to reduce the dilution of the CH grease, but will then fill her up and take it for a spin to see what happens.

Checked it yesterday and it turns out that all but an ounce or two has already leaked out the bottom so I won't have to worry about much mixing of the 90W and the Corn Head grease.

papagood, once I get the bottom bar and stump jumper pan off I should be able to see if there's any value in pressurizing the box. Based on how quickly the 1.6 gts of gear fluid leaked out while sitting still I'd say I somehow tore up the seal, or didn't seat it properly when I rebuilt it. I just can't imagine how it wouldn't since there's really only one way to install it. We'll see.

[thawhacker]

I have had briars wrap around my drive shaft and tear out my seal on the front of the gear box. Maybe something crazy along those lines happened underneath your bush hog.

[WoodieSC]

I have had briars wrap around my drive shaft and tear out my seal on the front of the gear box. Maybe something crazy along those lines happened underneath your bush hog.

Good point. I'll find out as soon as I can get the tractor started.

As I was inspecting the gear box last weekend, I was also filling the tank up from my above-ground diesel tank when it started sputtering and 'choked out' before I could turn it off. I thought it was just a plugged fuel filter, but even though I haven't had a problem like it in 20 years of use I determined yesterday that there was some apparently some water in the tank that got into the fuel lines.

Lately, if it ain't one thing it's another...

[thawhacker]

I know your pain, when it rains it pours!

[WoodieSC]

Just posting the 'final' (hopefully) story in case it helps anyone in the future...

I dropped the pan and blade bar to get to the bottom of the gear box expecting to see a torn up seal. However, everything looked like I'd just put it together, EXCEPT for some remaining gear fluid running right down the bottom side of the shaft. It was coming from the inside edge of the seal, right down some imperfections in the shaft. I took things apart and determined the the O-ring that sits in the top rim of the collar, right below the lower bearing was too loose and wasn't sealing the shaft, whereas the outer seal appeared to be doing as best it could. I ended up putting a tighter O-ring on AFTER I coated the area with Permatex 2 along with slipping a shim ring between the bearing and the collar O-ring to minimize wear.

Then put things back together and packed the gear box with JD Corn Head grease, so we'll see how that works out.