Bush Hog 286 splines still viable?

DieselBound · Jun 24, 2019

I was hitting some heavy brush (and high ground) and felt a significant judder. Nothing that has happened many times in the past. The speed had dropped down and I figured I'd just caught too much ground (which I had). I lifted the BH up and pulled forward figuring I was out of trouble. Set the mower back down and realized that it wasn't cutting. PTO shaft was spinning. Shut things down to find that the stump jumper was GONE! Took me, the wife and the dog to locate it in some heavy brush: it was VERY hard to find.

When I'd gotten this BH, a couple years ago, I noticed that the stump jumper was a bit loose so I tightened it up: I'm guessing that my mistake was that I didn't flip it over to do this- gravity wasn't helping me. Anyway...

Here are the stump jumper splines (a couple were showing fresh wounds from its departure from the shaft, but not sheared or broken, just roughed up (perhaps it was from the castle nut?).

Here's the gearbox shaft.

Does this look good enough to reassemble? I'd clean things up real well, and I'd reinstall with BH flipped over (and tighten with my impact).

Exchanger · Jun 25, 2019

It doesn't looks like so bad. Try to put one or two washer under the castle nut.

bullbreaker · Jun 25, 2019

If not : DN Equipment - DN Equipment

RoyKing · Jun 25, 2019

new stump jumper

RickB · Jun 25, 2019

Give it a try. Get it tight then smack the blade bar with a sledge hammer a couple times, then tighten. Repeat till you cannot get it any tighter.

TMGT · Jun 25, 2019

Actually they dont look too bad, remember they are tapered so it looks more worn in that picture. Might want to just clean them up a little with a file to make sure there aren't any burrs or distortion that would keep it from seating all the way.

Zebrafive · Jun 25, 2019

First time you tightened it did you put a cotter pin in? I can see the remains of one in the shaft picture.

DieselBound · Jun 26, 2019

I cleaned everything up and set the stump jumper back in place. The shaft is about 1/3" down from the top of the stump jumper's splines. Picture makes it look like the splines aren't lined up, but I just went out and took a look and it looks fine. Now I'm wondering whether I should pull it off and rotate it a bit to see if it wants to mate up better.

Zebrafive, yes, I'd put a new cotter pin in (I believe it was new- if not, it was in good enough shape) when I tightened it up: I don't recall how I tightened it up, maybe impact gun?

I ordered up a new castle nut and washers. Based on the price I'm hoping that the nut is a grade 10! I'm wondering how to go about torquing this up. The manual says that torque for a 30mm "fastener" (they show a bolt, but I figure it would apply to the nut) that is grade 10 (10.9) is 449 ft-lbs, grade 8 is 324 ft-lbs. I have 3/4" breaker bar and sockets, and I have a 1/2" air impact that's rated for 1,300 ft-lbs. Which should I look to use? (I know there's some way of calculating force for a breaker bar + cheater; perhaps this is the more appropriate way.) I don't want this coming off again as it's likely that if it happens again it'll for sure require some really expensive parts!

RoyKing · Jun 26, 2019

You to determine the amount of contact area and where it is. I would wire brush both parts and then dykem blue the shaft install and remove and inspect. You need contact at the top and bottom otherwise it will wobble and loosen

DieselBound · Jun 27, 2019

And if there isn't sufficient contact area (still not sure how I'd make that determination)? Would it be the stump jumper or the shaft? If it's the shaft then I really don't think that it's worth the headaches (juggling way too many things as it is): I got this thing pretty well beat up.

What is "normal" as far as how much I might expect the splined surfaces to draw together when torqued? As mentioned, I've got something like 1/3" (or perhaps 1/4") of the stump jumper above the end of the shaft's splines. Is it "normal" to have it start out with this much "gap?" I've never had a stump jumper off before, so nothing to compare to.

RoyKing · Jun 27, 2019

Like TMGT said file off the proud spots from peening when it was loose. Need some contact on top and bottom, tighten hammer some tighten again.

RickB · Jun 27, 2019

UYou need to have a gap at the bottom of the shaft, that’s is the way tapered splines work. Use the info already posted to get the castle nut as tight as possible, install the cotter pin and go use the cutter. Do not overthink this. It is not a precision instrument or brain surgery.

DieselBound · Jun 27, 2019

Rick, yeah, that's what I figure, but... I was just wanting to know what was "normal" as far as that gap goes (one could not see it at the bottom, but I'm figuring that the gap at the top would correspond the same). Maybe this thread can, eventually, vet this all out (and provide a reference point): I might know right away, or I may not know for some time (it took about 2 1/2 years for this to appear- in the future I'm going to be a bit more diligent a bout checking for play- I'd never had an issue with other mowers, though only 5-footers running off of smaller tractors).

The splines, other than a couple on the stump jumper that had their surfaces at the outer end superficially scuffed up by what I figure was hitting the castle nut?, don't look askew. I'm just a bit nervous after hearing other folks having messed up splines and requiring extensive repairs.

Am I right in thinking that the stump jumper will have wobble until it's firmly seated?

RickB · Jun 27, 2019

When the tapered shaft and hub are fully seated there will be no movement of the hub on the shaft and the stump jumper will turn without any appreciable axial runout.

DieselBound · Jun 27, 2019

So, if I get the right torque on it and it doesn't have any movement then it should be OK, yes? I seem to recall that I was able to take out the play before. Wondering why it let loose? Is it common for them to loosen up? (again, never experienced this before)

I'm still uncertain of the torque spec on this. Bush Hog just has general specs for bolts, no specifics for this nut. I asked the parts vendor and was told that he thought that it's a Grade 8: that would be 325 ft-lbs (based on 30mm wrench size).

RickB · Jun 27, 2019

I can’t say why it came loose, once in a while they will. Let that impact rattle on it, the vibration will help seat the taper. Run it and check for looseness after the first couple of uses and periodically thereafter.

DieselBound · Jun 27, 2019

My impact is rated up to about 1,300 ft-lbs. Any concerns that I could strip things?

I've been meaning to get something to set higher torque values and am thinking about getting a torque multiplier.

I did put anti-seize on the splines, in which case that should help them a bit. But nothing on the threads (and no plan to).

RickB · Jun 27, 2019

Use a little common sense, don’t tape the trigger down and go for coffee! Don’t waste your money on a torque multiplier, you aren’t going to strip the threads on the nut or shaft.