Loose gear box on bush hog

[TVZ]

I was running my old KingKutter bush hog through some fairly heavy brush when it started sounding more rattly. Upon looking I saw that all four of the bolts that hold the gear box onto the top of the deck were loose!

I guess I need to get the stump jumper out of the way so I can hold the nuts down there so I can tighten the bolts. But my question is, how could this have happened? How did all four bolts work their way loose? Is there an underlying problem that caused this?

 

[WranglerX]

Ever heard the phrase S*** happens.... Check blades and stump jumper for excessive out of balance..... Suggest lock washers, nylock nuts or Loctite threadlocker when putting it back together.... Also inspect area around where gearbox bolts down for cracks and or metal fatigue....

 

[mrmikey]

As Wrangler said, crap happens. The bolts and nut are probably toast now. Get new gr.8 bolts, locknuts and gr.8 flats. IMHO lockwashers aren't worth crap, they break, add no load spreading to the clamping surface and only come into play when they're already loose. Check the holes and I bet you're going to find them wallowed out so be prepared for either a couple larger size gr.8 flats or some welding.

 

[Beaver Cove Deere]

No big deal. I had a 72” Land Pride that loosened up. I replaced them with fine thread hardware and locknuts.

 

[ArlyA]

I agree with most advice already given here. If it was mine, I check what grade of bolts the OM used and replace them with the same, or higher. And replace all fastener components like washers, lock nuts, etc etc.

 

[SPYDERLK]

I was running my old KingKutter bush hog through some fairly heavy brush when it started sounding more rattly. Upon looking I saw that all four of the bolts that hold the gear box onto the top of the deck were loose!

I guess I need to get the stump jumper out of the way so I can hold the nuts down there so I can tighten the bolts. But my question is, how could this have happened? How did all four bolts work their way loose? Is there an underlying problem that caused this?

Joint movement from under tightened bolts. Replace w/Gr8 bolts and Gr8 washers. Tighten to FULL bolt spec. -- Depending on size, probably 200ft-lb or more.

 

[SPYDERLK]

As Wrangler said, crap happens. The bolts and nut are probably toast now. Get new gr.8 bolts, locknuts and gr.8 flats. IMHO lockwashers aren't worth crap, they break, add no load spreading to the clamping surface and only come into play when they're already loose. [[[Check the holes]]] and I bet you're going to find them wallowed out so be prepared for either a couple larger size gr.8 flats or some welding.

If no cracks yet you can probably get away with adequate clamping to "freeze" the joint. -- The good bolts and washers, TIGHT, will do that.

 

[Williy]

If you don't trust the lock washers or lock nuts by them
selves then use both along with some locklite

willy

 

[Alan W.]

Same thing happened on my King Cutter. The lock washers broke and left the gap.
Pulled the stump jumper and replaced with grade 8 bolts and lock nuts.

 

[EddieWalker]

I figure it's just part of owning equipment and using it. When it happened to me, I replaced the bolts and nuts with brand new. Some of the threads had worn away and I wanted brand new locking nuts with the plastic on them. I also used red Loctite on the threads.

You don't have to remove the stump jumper, but somebody is going to have to reach in there with a wrench to hold that end of the bolt, while somebody else is at the other end.

You never want to remove the stump jumper if you REALLY DON'T HAVE TOO!!!! It's a really painful thing to do, they are stuck on the gear shaft, and it's never an easy thing to get it off of there.

 

[mrmikey]

.........brand new locking nuts with the plastic on them

Said with respect Eddie, they are gr 5 not 8 and the threads will stretch if they're under any type of constant vibration.

 

[EddieWalker]

Said with respect Eddie, they are gr 5 not 8 and the threads will stretch if they're under any type of constant vibration.

Are you saying the nuts are grade five? I’ll have to double check. I bought them from McMaster Carr and thought the bolts and nuts where both grade 8 when I changed mine.

 

[mrmikey]

Are you saying the nuts are grade five?

Years....decades ago actually, I was to a fastener course. One of the few things I remember is that any locknut with the crimped/deformed section to hold the nylon insert was gr. 5 as gr. 8's couldn't be crimped like that. Supposedly that's why a gr.8 locknut is deformed by squeezing the taped part of the nut in.
Saying that, looking for this pic, they have gr. 8 with the nyloc insert so things have changed.
My apologies Eddie.

 

[Sawyer Rob]

We have a VERY good fastener place here, NO junk china bolts from them!

They insist that "crimped" lock nuts hold better than nylocks, (plastic) so when it really matters, all I will use is crimped nuts AND like on my rotor blades, I also use loc-tite along with them.

SR

 

[Alan W.]

All I know is the nyloc nuts are as tight as ever and it has been 5 years or better since I changed to them.

 

[Williy]

Use a #8 bolt with a wide nut drill small hole and use
a clip similar to this:

willy

 

[SPYDERLK]

Just tighten it up extremely tight! It wont move. It wont loosen.