Driveshaft into Rhino 160 Transfer Case....Issue

[tc3longhorns]

Good Afternoon,

I have a L3400 with a Rhino 160 mower. I recently snapped the pin connecting the Driveshaft to the transfer case. No big deal, stop the pto. pull up to the barn get another grade 8 bolt and slide everything back together. Except the Drive shaft gets about 7/8 over the male end of the transfer case and stops.

There are no burrs or projections stopping the mounting. There seems to be rings of some sort.

Thoughts, ideas, suggestions? Do you need a special tool to make this happen?

 

[Eric McCarthy]

First things first and get rid of the Grade 8 bolt and replace it with a Grade 5. I know Grade 8 is a strong bolt and it'll hold up, but you DO NOT want to trash and destroy the rest of the mower. That shear pin is put in place for a reason, to protect you and protect the mower from SEVER damage.

 

[bosshogg]

I believe all shear bolts are designed to be Grade 2 or no grade bolts. You want the bolt to shear instead of doing damage to the tractor or mower gears.

 

[Eric McCarthy]

Oh thanks! I couldn't remember off the top of my head if it was G2 or G5, but I know its definatly not G8.

 

[Kytim]

The others are correct, use a grade 2 bolt (bolt without any dashes on head) for a shear pin/bolt. In single shear applications a G2 1/4" bolt will withstand a little over 2100lbs force, PSI. remember single shear is when 2 flat plates are bolted together. a G8 in same application would take well over 4400 lbs force, PSI. (read as broken internal parts) Now in a rotational double shear application like a drive shaft the forces are exponentially higher. The nominal tensile strength, the pulling apart of itself along its length of a G2 is 74000 psi MAX while the same size G8 is 150,000 psi. and these are just plain steel fasteners. Different alloys will change those numbers as well. When considering bolt size, shear strength increases while after a certain size, 3/4" nom., tensile strength goes down. In other words, that extra grunt tightening something may not always be a good thing, thats what torque figures are for. Also a graded bolt like a 8.2 should not be placed as a sub in a grade 8 high heat application, the heat WILL cause a premature failure.

Now as for your other trouble, pull the shaft and look at the face of the gearbox, they, the rings had to come from somewhere. It,they may be retainer rings for the seals or bearings that have failed. Find out, don't ignore them may save you some big bucks in repair costs.

Now if your shearing those bolts on normal ground without hitting obstructions you may have an inappropriate equipment to HP match. If your breaking shear pins because your running over lots of stumps and obstructions that would be operator error. because it would be using the equipment outside of the implement design.

I myself would sure hate to break an internal transmission shaft because a shear pin didn't do its job.

Good luck!

 

[Eric McCarthy]

After re-reading his post again he stated that he got "another" grade 8 bolt and replaced it. With that being said it sounds like shear pins have been broken before and replaced with grade 8 bolts. My thoughts are that sever damage is already done to the pto shaft and the gear box. Sounds like somethings already stripped.

 

[Kytim]

I'd sure be looking at that front gearbox for damage and lube while I was there.

 

[gpreuss]

My bush hog has a 3/8" bolt... It has sheared once in 35 years, and that just recently. I figure the bolt is to protect the tractor more than anything else - I would hate to have my thousand dollar mower wreck my twelve thousand dollar tractor.
None of us have addressed the problem of the driveshaft hub not sliding down on the gearbox shaft. I'm confused. There has to be a burr somewhere there, preventing it from going together. This is not rocket ship precision - you can file, grind or polish the shaft as you need to. Same for the hub. I suspect when the bolt sheared it gouged the inside of the hub.

 

[Lil Foot]

As always, pics would be helpful.