3pt not working, not sure what I broke

[BeezFun]

B2710 with HST, I was using post hole digger and tractor was really laboring, our soil is really rocky. I heard/felt a loud bang so I stopped. Here's the situation:
* 3pt arms won't raise. they dropped to the ground freely and I can raise them by hand, but the hydraulics won't lift them.
* PTO shaft turns, but I can't put a load on it so I don't know if it really works.
* The tractor will move but it makes a bad noise like there are parts clanging around in the transmission.
* I have the proper shear bolts on the auger, neither of them failed but were very bent. The bolts on the PTO shaft did not shear either.

Trying to decide how to proceed, it seems almost certain something broke in the rear PTO section of the transmission. I also think the clutch may have been slipping while this failure occurred. I noticed after the loud bang when I looked the other direction that there was smoke coming from under the tractor. The wind was carrying it in the opposite direction I was looking when things broke, so I'm not sure how long that was going on. The noise when I drive it might be some broken part that ended up in the transmission where it shouldn't be. I'm reluctant to drive it given the noise it makes, it's only a few hundred yards from the shop so maybe I can tow/shove it into the shop.

Any advice on diagnosing this before I tear into it is welcome.

 

[diesel85]

You likely broke the lift rod in the cylinder case or cracked/sheared the lift arms.

Since there is noise emanating from the transmission, I also have reason to believe there might be carnage done to the PTO gearing.

I would tow it if you can.

Post hole diggers are rough on machinery in rocky and heavily rooted soils.

 

[BeezFun]

Tnx, I'm going to borrow my neighbor's tractor to tow it into the shop. I have to stare at the shop manual for awhile and see if there's a cover on the 3pt area so I can look in there without taking everything apart.
I'm especially pissed that the shear bolts didn't break, I'm neurotic about using the right bolts on equipment. You're right, rocky soil is hard on post hole diggers. In the future I'm going to rent a skid steer to do stuff like this.

 

[rScotty]

Before tearing into it, what I do is get the parts manual and use the illustrations to do some basic diagnostics. Right now it's hard to say just what broke, but I'd bet that if a person were to study the exploded parts diagram for awhile it would be possible to make a pretty good guess. For example, does the transmission shaft that drives the PTO drive anything else? Does any part of it share connections with the 3pt hydraulics?
BTW, how many hydraulic pumps does a B2710 have? some HST tractors have several. If so, which one works the 3pt, and is there a port where you can check it for pressure.
Just simple things like that..

Most of the damage that I've seen post hole diggers do to 3pt lifts and PTOs was done not by overloading the tractor hp wise, but because of the 3pt lift arms put a bind on the PTO shaft and either broke the PTO shaft or the housing.
rScotty

 

[BeezFun]

When I try to tow it, the rear wheels move a bit then lock up and skid, same going backwards. I tried it with the HST lever in neutral and in each gear, same behavior. Pushing clutch in doesn't help. I decided to put it in low gear and go slow. It makes a repetitive noise that sounds like something grinding, but it's not too loud and I only had to go 100 yards. So it's in the shop now.

 

[BeezFun]

Before tearing into it, what I do is get the parts manual and use the illustrations to do some basic diagnostics. Right now it's hard to say just what broke, but I'd bet that if a person were to study the exploded parts diagram for awhile it would be possible to make a pretty good guess. For example, does the transmission shaft that drives the PTO drive anything else? Does any part of it share connections with the 3pt hydraulics?
BTW, how many hydraulic pumps does a B2710 have? some HST tractors have several. If so, which one works the 3pt, and is there a port where you can check it for pressure.
Just simple things like that..

Most of the damage that I've seen post hole diggers do to 3pt lifts and PTOs was done not by overloading the tractor hp wise, but because of the 3pt lift arms put a bind on the PTO shaft and either broke the PTO shaft or the housing.
rScotty

Totally agree, I was looking at Messick's parts diagrams while I was eating lunch. I have a service manual, it looks easy to get at the top part of the 3PT area. There's only 1 pump and I have 3 remotes on the back, so it's easy to check pressure. Although the FEL works fine so I think the hydraulics are OK. I wish I didn't have another project I have to stay working on, I'd like to spend more time on this because it's bugging me.

 

[Cycledude]

Shear bolts shouldn’t bend they are supposed to shear. Do the holes for the shear bolts have excessive wear ?

 

[5030]

I hope you were idling the tractor when you were using the PHD... Idling is always the best approach. I even idle my M900 with a PHD. That way of the auger encounters something down there, it kills the tractor engine.

Sounds like you weren't. Also sounds like a split is coming.

 

[BeezFun]

I hope you were idling the tractor when you were using the PHD... Idling is always the best approach. I even idle my M900 with a PHD. That way of the auger encounters something down there, it kills the tractor engine.

Sounds like you weren't. Also sounds like a split is coming.

Started out idling, when the engine started to labor I made the mistake of increasing speed instead of quitting. I'm close to having the top off the 3pt section of the transmission, hopefully I can look inside and figure out what broke.

 

[rScotty]

Shear bolts shouldn’t bend they are supposed to shear. Do the holes for the shear bolts have excessive wear ?

Good point. Shear bolt calculations are based on the shear edges being at right angles; not rounded over.
Let's think about it for a moment.

OK, just did some quick review on shearing forces. Holding everything else equal, the force required to shear the bolt is simply dependant on the area of the bolt shank. It's not like the cutting edge of a knife. So a little bit of rounding on the edges of the holes doesn't change calcs enough to make much difference - the shearing still happens along a similar path through the bolt.

What that means is that the force required to shear the bolt shouldn't begin to rise until the bolt bends enough to make the shear path longer in the bending direction. Here we're assuming that the other dimension stays roughly the same as the original bolt diameter.

Bottom line: the edges of the shear holes can be rounded, just so long as they aren't rounded so much that the bolt can bend before shearing.
rScotty