Rotary Cutter Grease instead of oil......

[JonDyana]

I'm looking at buying a 5FT Bush Hog SQ60 as a second Rotary Cutter. Two questions:

1 - The Gearbox is nice and tight. No slop - very nice. When I pulled off the fill plug to inspect the condition of the lubricant, I was surprised to find the old (deceased) owner was using grease instead of gear oil for lubrication. I stuck a screwdriver into the box and the grease I removed didn't SEEM to have any noticeable metallic filings or other contamination. I use 80/90 gear oil in my cutter - should this be a deal breaker?

2 - The PTO shaft on this unit protects the tractor by using a sear bolt at the gear box spline. Any thoughts on converting it over to a slip clutch? Cost isn't as great a concern as protecting my tractor........

Thanks in advance!

 

[mcfarmall]

There's nothing wrong with using a semi-fluid grease in a gearbox. NLGI 00 is used in lawn tractor gear transmissions all the time. As far as the slip clutch is concerned, a shear bolt doesn't offer any less protection for your tractor than a slip clutch. You just have to stop and replace it if it breaks. After you do this a few times you will learn to stay away from solid objects like stumps, etc. and life will be good.

I've run a shear bolt driveline on my cutter for 30 years and maybe replaced it 3 times.

 

[teg]

Grease in the gear box is fine, I would not worry about that. Usually grease is used in place of replacing the seals. Also, yes you can add a slip clutch. You may have to shorten the shaft.

 

[JonDyana]

Good news....Thanks!!

 

[Rustyiron]

Keep in mind that you should use a certain (semi fluid) grease like mcfarmall said. "Common" (u-joint - loader pin, etc.) grease is thicker than the "00" or "000" or "corn head" grease and things might have to get a little too hot before they properly lube things.

 

[dfkrug]

Keep in mind that you should use a certain (semi fluid) grease like mcfarmall said.
"Common" (u-joint - loader pin, etc.) grease is thicker than the "00" or "000" or "corn head" grease and things
might have to get a little too hot before they properly lube things.

Yes, thick grease can be a problem as it does not get into all the places it should, as an oil would.

I have seen the results of thick grease in a rototiller chainbox.....completely worn out chain. Rototillers,
like mowers, commonly get twine lodged into their shaft seals, causing all the gear oil to leak out.

A semi-fluid grease is the way to go, as you say.

 

[JonDyana]

I dug up a service manual for that unit online and they actually did approve the use of "00" in the SQ series gearboxes along with several other lubricants. Thanks to everyone for your help. Buying the unit and improperly lubricating that gearbox would have made "a good deal" NOT such a "good deal." I really appreciate everyone's input.

 

[Texasmark]

Units come new with 80W-90 or 85W-140. Well used ones come with no oil or grease. I use Lubriplate 105 which is about a 00 grease, between oil and grease so it flows slightly but not all that much and stays in the gearbox.

Other thing is boxes didn't used to come with vented fill plugs. They do now. Vented plugs allow pressures built up during mowing to vent rather than push your gear oil out your lower grease seal on the cutter shaft.

I don't like slip clutches on a shredder because they are hard to set right and unpredictable....you don't know if they will slip when you WHACK something. The bolt is your best bet for dependability and reliable protection. Carry spares suitable wrenches, a hammer and a punch. Use grade 2 as they will hold a lot of times when a 5 or 8 will snap (brittleness gives them their temper for working in tension....here you are in shear). Also use with a nylon insert locking nut that is just snug or a little loose against the coupling. Having a little slop makes them work longer for me. Unless you are mining trees, you'd be surprised how seldom you pop one with a stump jumper and pivoting blades.

 

[Fallon]

I put grease in my old flail mower gearbox rather than replace seals.

My rotary cutter allegedly had a clutch. Went to do the annual maintenance on it at the start of year 2 & found only a bolt under the shields. I was pissed at the time. My tiller takes me half an hour to adjust & clean the clutch. When I sold my rotary after 3 years I had 0 minutes of maintenance on drivetrain protection (outside of taking off the guard).

I'd go with a sheer pin unless you plan on hitting a lot of stuff & end up sheering a lot of bolts. Otherwise sheer pins will be a lot less effort.

 

[teg]

IMHO, a slip clutch (especially one that's not maintained / adjusted) is a waste of money. A shear pin works just fine. I screwed up and let the tractor's clutch out to fast and sheared the pin that was holding my slip clutch on. :mur: