Crack in Bush Hog Gearbox

JWR · Jul 15, 2015

Model 297 Bush Hog brand. Normal pasture clipping and some brush but nothing huge. Might have 50 to 70 hours on it. Using 81hp tractor to run it, well within specs on everything. Never hit anything catastrophic (like a big stump or boulder...) Found a horizontal hairline crack in the gearbox housing maybe an inch or two above the bolt pattern. Only noticed due to oozing gear oil.

Anyone else seen this ?

boggen · Jul 16, 2015

manufacture defect maybe? improper setting of the slip clutch? slip clutch was not maintained to slip like it should.

if under warranty get it replaced. there is a good after market for gear boxes out there. double check hole pattern, and spline sizes for going to slip clutch and then down to stump jumper. and bigger issue make sure ratio is correct. and if using 540 vs 1000 rpm setup.

http://www.bushhog.com/uploads/documents/RC295-297-SPEC.pdf
showing 1 year limited warranty with a 5 year gear box warranty.

50-70 hours i would imagine you would be within warranty. even just running it 15 hours a year...

JWR · Jul 16, 2015

This was bought as a brand new unit and the slip clutch appears to be set right and working well. It was adjusted. I don't have a high rpm pto, just the std 540. It's under warrantee, not worried about that. Just wanting to hear if others have seen this problem and if there are theories about the cause. The mfr says they have seen it before and cannot explain it. As a mechanical puzzle, I cannot see how anything done with that bush hog could create a force to split the thick heavy gearbox casting like that -- at least not in that location. This is just a hairline crack at the left rear corner of the gearbox. Seems to me like it may be a casting defect.

boggen · Jul 16, 2015

crack could be from the chunk of metal the used to making the case with. and the crack coming from the actual metal foundry. ((assumption is... company orders a really large chunk of metal. then cut it down with some lazer cutter or like, then they put it into various machines to lath it out cut it up, to make final piece)) the large chunk of metal from foundry could of had a hair line fraction or like in it and it was simply missed.

if it was a poured casting, perhaps something happened during the pouring or cooling stage.

never actually seen it in real life, that i can remember. but when learning of how metal is made and how you manage it, (lots of youtube videos, and various internet websites, that deal with testing metals). i do remember seeing above. its kinda like diving into log that you are going to widdle away out to make a statue or something, and coming across some sort of knot or like that was not expected to be seen in the lumber maybe instead of a knot some sort "nail" or like.

brown40 · Jul 16, 2015

Was it right above a bolt or somewhere in the body? If it was right on a bolt head there could be some pressure from a corner on the casting, but I would guess they are saving some weight on the casting or using some rough stuff. I think most are coming over in ships. What is the thickness of the gearbox flange and casting area that cracked, do you figure?

JWR · Jul 16, 2015

In this photo the hairline crack is at the corner of the gearbox halfway between the two bolts. Note the lube that has seeped out. The crack cannot be seen even when this is blown up, but is horizontal and about an inch above the flange. The crack is maybe an inch or 1.5" long and wraps around that corner. I can't tell how thick the metal is but from the overall shape/size of the gearbox I'd think it is at least a half inch thick. Seems to me to be a casting.

The spec sheet says it is rated at 130hp with min recommended of 55 hp. I use a MF2660 with 81hp.

Sawyer Rob · Jul 16, 2015

I believe Bush Hog gear boxes are made in china, so who knows what went wrong!

SR

Kyle_in_Tex · Jul 16, 2015

7 foot cutters are hardest on gearboxes and spindles. Physics. that's why they are not common.

Hope you can maybe get it repaired or replaced cheaply.

JWR · Jul 16, 2015

The manufacturer is backing it. Just downtime, and expense of time & transport to the dealer. Bush Hog has been very good about it AND admitting they have had some of these failures and do not know why. Say their supplier does not understand the cause either. No idea where it was made but has the Bush Hog name in raised letters on the gearbox.

I'd just like to hear if others have this issue and where their gearbox cracks were. Curious. Hopefully the replacement will be durable.

Turbys_1700 · Jul 17, 2015

I've bush hogged many years. Never had a crack in a gearbox housing. Never used a 7' unit though. Most of my experience was with old 305's, 306's, and squealers in 5 and 6 foot widths. Have used a multi spindle Howse 10 footer and just purchased a 6' 472 Brown. I agree with Kyle that a 7 foot single spindle cutter will be harder on the gearbox than multi-spindle units just due to physics. I don't think though that Bush Hog would spec a gear box that was not properly designed for the type of stresses encountered with a single spindled 7 foot cutter. IMHO the most reasonable cause would be a bad casting where the crack is. It happens but is not common. The main thing is that Bush Hog and the dealer is standing behind the product to get your issue resolved.