I destroyed the gearbox on my brush hog.... help

[LittleBittyBigJohn]

Put me down on the list that says get a gearbox and mow on. Looking at tractor data, your machine should have 45 hp at the PTO when new. I don't see that destroying a 40hp gearbox in the short or long term. I think LD1 has a good theory, pinon shaft backed out and extra backlash wore the gear set out.

 

[John0829]

That gear box failed for some other reason, definitely NOT what you did hitting the stump. I have a 40hp gearbox on mine and my rule is if the tractor can safely ride down the brush it gets cut. As has been said the shear pin is there to protect the gearbox and I have found most of the time they shear way to easy, that is why I finally put a slip clutch on mine.

 

[Horse Family]

What bolts were loose on the gearbox?

If they were the bolts that hold the input shaft in.....that could explain it. As the input bolts get loose, it would allow too much backlash (clearance) between the gears and they could wipe out as pictured.

You mentioned leaks. Did it ever run low?

While I agree that a 40hp gearbox on a higher HP tractor shouldnt be an issue....as a shearbolt or clutch should protect it regardless. But this dont look like impact damage. Just looks like wear either from backlash adjustment or lack of lube.

But who you bought the cutter off of....was using it correctly. 40hp light duty cutter for pastures that look like lawn. They arent built to smack stumps and hog brush. So if that is your future intended use, you need to look for a heavier cutter. Most all cutters are rated at a certain "capacity". That meaning the diameter of tree saplings/brush they can handle. And most light duty ones are only rated for 1" or less saplings. Which is quite small....like only a little more than half a golfballs diameter.

Medium duty cutters are usually 2", heavy duty 3" and very heavy/extreme 4".

And with each increase in capacity, the gearboxes get much higher ratings. 3" capacity cutters usually have well over 100hp rated gearboxes.

The first bolts i noticed that were loose were the bolts holding the gearbox to the top deck of the tractor. I had to remove the stump jumper in order to tighten them down. Two the the four bolts were missing the lock washers. I tightened them all down, and then after using the brush hog more, the same ones came loose again. So I retightened, this time with red locktite.

We did notice that the bolts around the input shaft had also gotten loose.

I think I have learned that in the future, if I buy any used equipment, that I will do a much more thorough look over of the equipment, as well as taking the time to go through it and check all bolts etc.

I do think that after I repair this one, I will sell it, and look for something that is a heavier duty cutter.

 

[2manyrocks]

By the time you make these repairs, you know what you've got vs buying another used cutter unless its new.

Bolts may be coming loose due to vibration or perhaps new bolts, washers, etc., would finally tighten enough to not loosen up? Do bolts actually wear out and loose their ability to stay tight?

 

[Horse Family]

You guys are awesome, I so appreciate the help and feedback. So its clear I need the new gearbox, now just trying to figure out which one to get -

On Surplus center, all the RC51s are ratio 1:1.93

According to the tag on mine my current ratio is 1:1.47

how important is it that the gear ratio remains the same?

I see they have some RC30s that appear to have the same gear ratio as mine - 40 HP Omni Gear RC-30 Rotary Cutter Gearbox 1:1.46 Ratio Model 250001 | Featured Items | www.surpluscenter.com

But I don't know what the difference in the two are.


I also see this one at agri supply - seems to have the same HP rating and ratio - Gearboxes-Rotary Cutter Gearbox

If anyone has any experience and can help me choose id appreciate it!

 

[5030]

I agree, the previous owner started the destruction of the gearbox, all in takes is one chipped tooth to start the destruction and because multiple teeth engage the pinion at one time, you won't feel anything until multiple teeth are destroyed, except maybe a little vibration.

Couple of other items that need to be addressed:

One, lift the cutter up and make sure the blades are FREE swinging, They have to be free and not rust locked to the pivots and if they are badly worn, replace them... I'll give you a web site where they will have EVERYTHING you require and their pricing is excellent and service is as well. I get all my replacement parts for both my shredders from them as well as 3 point parts like bushings and overrunning couplers, something you really need for ANY shredder as a shredder will destroy your PTO brake in pretty short order from freewheeling if the PTO is disengaged while the shredder is turning at operating rpm.

You can get everything you need, including the pivot bolts and lock nuts as well as the blades and gear box and even the correct shear pins (something you need and not Grade 5 box store pins) from Agri Supply. I think their website is www.agrisupply.com, if not, look it up on Goggle or Duck Duck Go, whatever browser you use. I buy a ton of stuff from them, shipping is very reasonable, delivery is always excellent and nice folks to deal with.

 

[5030]

Do bolts actually wear out and loose their ability to stay tight?

Especially if not torqued properly and Locktited. I use thread locker on everything threaded, subject to stress and vibration. Usually Blue Threadlocker but sometimes (depending on application), red high strength and not the knock off Chinese crap either. Always Henkel Loctite. USA made (sometimes Mexico) but never China. It's not cheap but the good stuff never is today. I buy it in 250ml bottles.

 

[ROUSTABOUT]

You guys are awesome, I so appreciate the help and feedback. So its clear I need the new gearbox, now just trying to figure out which one to get -

On Surplus center, all the RC51s are ratio 1:1.93

According to the tag on mine my current ratio is 1:1.47

how important is it that the gear ratio remains the same?

I see they have some RC30s that appear to have the same gear ratio as mine - 40 HP Omni Gear RC-30 Rotary Cutter Gearbox 1:1.46 Ratio Model 250001 | Featured Items | www.surpluscenter.com

But I don't know what the difference in the two are.


I also see this one at agri supply - seems to have the same HP rating and ratio - Gearboxes-Rotary Cutter Gearbox

If anyone has any experience and can help me choose id appreciate it!

2 to 1 cuts better. If I'm looking at a cutter, if it ain't close to 2 to 1, meself will let it pass. That babe will cut grass like a lawn mower.

 

[LD1]

Not sure the difference. They seem to read and spec nearly identical

 

[2manyrocks]

Can't go crazy with it, but if you want a bolt tight, a breaker bar seems to get a bolt tighter than a short handle ratchet wrench. Given the labor involved to fool around re-tightening bolts, I'd think about installing new bolts, nuts, washers, and lockwashers along with locktight as 5030 recommended. I'd also clean the mounting deck surface in case rust is keeping the bolts from firmly locking in place.