Brush hogging with Montana 3840, Grade 2 shear bolts wont work

   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #1  

tdpalms

New member
Joined
Sep 12, 2023
Messages
9
Location
New Underwood, South Dakota
Tractor
Montana 3840
Does anybody have any experience with brush hogging on their Montanas? I hadn't gone through a single shear bolt on mine since I bought it, and once I did it was a nightmare. I bought a pack of grade 2 bolts from Menards, but sheared every single one of them on startup, never even got to mow with them. Tried engaging the PTO at low idle RPM and normal operating RPM. Finally just put a grade 5 bolt in there and was able to mow with no issues. I know everybody says to never use higher than grade 2, so I'm wondering if I need to try feathering the clutch at low RPMs to get the shaft to start spinning much slower? I just don't want to continue using the grade 5 and end up destroying my PTO. It is an older 5ft HiCo rotary mower, no slip clutch.
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #2  
ALWAYS engage PTO from idle. I guess use grade 5 if nothing else? Otherwise check that driveline doesn't have any drag in it somewhere?
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #3  
I have a Frontier 60" brush hog that has eaten its share of rocks, roots and small trees and brush. The sheet metal has lots of dents that testify to its hard life. I have never broken the shear pin on it. I bought it originally to use with my old 8n, stalled it out a number of times with no damage to th shear pin.
I always start it at idle and feather the clutch in to get it spinning, I do this with all of my PTO driven implements. I did break a shear pin on the post hole auger once when it hit a big rock in the side of the hole.
If you engage the PTO slowly at idle it should last a long time.
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #4  
Engage PTO slowly while at idle. Check to be sure the cutter spindle is not binding. Stay with grade 2 shear bolt. Ken Sweet
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #5  
Well then there is this;
I wouldn't worry about using a grade 5 bolt. Does the manual for the brush hog specify grade 2?
Also the bolts used should have almost all of the threads outside of the 2 flanges. You should have smooth shank especially in the shear area.
The purpose of the shear bolt is protect the implement not the tractor.
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #6  
I had an 850 John Deere that had a 2 stage (foot) clutch for the PTO, that was an on off switch - just boom - full on. I learned to momentarily engage it to get the blades spinning a bit, and then fully engage it - all at idle of course.
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #7  
I tried to save some money, bought some generic bolts at TSC to use for shear bolts on my Bush Hog SQ172. Same specifications as the OEM bolts but they were threaded the whole length. Went through 6 in one day, said enough of that. Bought OEM shear bolts from the dealer at $7 each, that only have about a 1/2 of thread at the end. Haven't sheared one since.
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #8  
Did the original shear pin shear smoothly or was it smeared over? If smoothly probably was grade 5 since grade 2 usually smears and is harder to drive out and replace.
 
   / Brush hogging with Montana 3840, Grade 2 shear bolts wont work #9  
Raise the mower off the ground.
Can you spin the blades freely when the mower driveline is removed from the pto? Is the mower gearbox oil full and clean?
Just checkin.

I wish I could remember if I was using a proper shear pin or not… but a while back I backed my brush cutter over what I thought were very rotten logs… well they weren’t and boy o boy that was a mistake.
Long story short, the internal gears that drive the pto completely shredded and I had no more pto.
Was quite a process but I opened up the tractor and replaced the damaged parts

This never would have happened if the shear pin would have sheared.
🤷

These are what I get from Peavey Mart
 

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