PTO winch shear pin fitting

[Eurasiaoverland]

I've got a PTO winch for my 60 Series (they are almost identical to later 40 Series winches). In fact, I've got two, plus a third which I borrowed from a friend for reference. All however are old and well used. The shear pin bores are mostly drilled out or partly worn. This leaves me wondering how the shear pin fits from factory. Was it a light interference fit, snug in the bore, or slightly loose?

Pictures just for interest

Thanks

 

[charliemeyer007]

No clue for Toyota's. Sheer pins need a close fit so you can just push them in or more importantly push the stub out. When the holes get egg shaped it is easier to sheer the pin. Bushing the hole back to OEM size is the fix.

 

[Eurasiaoverland]

No clue for Toyota's. Sheer pins need a close fit so you can just push them in or more importantly push the stub out. When the holes get egg shaped it is easier to sheer the pin. Bushing the hole back to OEM size is the fix.

Thanks, that was my gut feeling. The original shear pins on the 40 and 60 Series winches are about 4.2 mm in diameter, but it seems these are very conservative in terms of shear strength. I also have a later (1990 on) 70/80 Series PTO winch shear pin, which is 5.0 mm in diameter, and which I plan to use. My good winch worm has a bore of 6 mm to I have ordered a 5mm ID/6mm OD tube to sleeve it.

For the winch yokes I have two - one seems to be about 4.5 mm on one side and 5-5.5 mm on the other (egg shaped). The other has been drilled to about 6.5-7 mm each side. I was planning to sleeve the holes in the yoke with the larger holes with short section of the same tube I mention above, and tack-weld them in place. I know welding stainless to cast iron with mild steel MIG wire is not ideal, but hopefully good enough for a tack weld. What do you reckon?

 

[charliemeyer007]

I would interference fit the bushing - heat the unit and dry ice the bushing - if it just slides in it should be perfect when the temp normalizes

The PTO on my deuce and half used like 3/8" aluminium sheer pins. They would only issue 3 pins. I could sheer the pins just letting out the clutch quickly with no load as in an empty spool not the 300' of 1/2 wire. I had my secret allen wrench and electrical tape to hold it in. I spent like up to 8 hours winching my signal rig and generator trailer up and down mountains. The snatch block was very handy at times. Winch up close to a tree, wrap a chain around tree and bumper, spool out wire to next tree. Pull line tight, remove the chain, back down far enough to clear the tree and then winch to that next tree. Coming back was harder than going up.

 

[SteveH]

I learned this in the field: when you shear a shear pin, the damaged (sheared) pin often jams in both the inner and outer holes. The broken bits do not fall out on their own. I bought a suitably-sized pin punch and kept it in my kit to remove the bits.

Part of the obnoxious nature of PTO winches is that after I broke the shear pin and the wire rope was still under tension, you then need to align the inner and outer shear pin holes so that you can drive out the remains of the shear pin and install a new one, along with cotter pins. This is somewhat dangerous and awkward. With a new pin installed, you can then relax the wire rope and figure out a new plan. I broke the shear pins while attempting to pull a stump in my back yard, so I (at least) was not dangling from a ledge at 14K feet in a lightning storm.

Perhaps there is a better method to replacing a broken pin in the field (please explain), but this is what I did. Be prepared for this.

 

[charliemeyer007]

There is no good easy way to remove the sheered pin that's stuck inside. Doing the tedious work to chamfer the inside of the holes edges first will make it easier to use the punch to drive out the sheered piece - aluminium usually gets big burrs from the wiping sheer action, steel ones tend to fall out when you align the threw hole.

Winching is hazardous by nature. Taking a few moments to ask yourself what happens if this (unit) fails?