L3800 HST PTO engages but with no real power

[barkster]

Hi everyone, this is my first post.

I came to own an L3800 HST from a land purchase I made about 10 years ago. The owner agreed to sell the tractor with the land. It was a relatively new L3800 HST with the LA524 front loader and a few implements, including a Land Pride bush hog.

Recently, while I was using the bush hog, I got off the tractor to take a break. When I climbed back on and tried to engage the PTO, the bush hog started spinning and the minute I went into the grass is slowed down and stopped. The cable to enage the PTO is working... I removed the bush hog and was able to engage and disengage the shaft from spinning using the PTO lever. I put the bush hog back on, engaged it while lifted off the ground and the blades began to spin. As soon as I lowered it into the grass, the blades slowed down and stopped. If any load is placed on the shaft (like the resistance of tall grass on the blade) it slows and stops, as if there is very little power being transmitted by the shaft.

My first guess is something in the hydraulic transmission is busted. The tractor still drives forwards and backwards, the fluid is visible in the site glass, the bucket still goes up/down, but the PTO gets next to no power. Any suggestions before I haul it to repair shop? Thanks!

 

[ctfjr]

is it possible it has something to do with the pto shaft? do you have a slip clutch that may be slipping? A shear bolt that sheared but there is enough friction to drive the unloaded implement?

 

[barkster]

is it possible it has something to do with the pto shaft? do you have a slip clutch that may be slipping? A shear bolt that sheared but there is enough friction to drive the unloaded implement?

Thank you! Clutch is engaging correctly for the Low/Med/Hi gear, PTO, and 4 wheel on/off. Of those two causes, a shear pin sounds more likely for the symptoms I'm seeing. I also hope that's an simple/inexpensive repair.

 

[Jim L.]

shear pin sounds more likely for the symptoms I'm seeing. I also hope that's an simple/inexpensive repair.

I suggest: with the tractor off and the three-point mower on the ground, open the shield on the top of the mower and find the universal joint after the PTO shaft. Between the mower gearbox and that universal joint, there should be a bolt head and matching nut visible. That is the shear bolt and its nut (with washer).

Take it out, if still there. It's common, Tractor Supply sells them as a card packet. Otherwise the bolt can be matched from a hardware store with a low hardness grade. To work correctly, it needs to be low hardness.

Simple repair. Engaging the PTO with slow clutch and low RPM's while blades are not loaded increase the bolt life expectancy.

 

[lugbolt]

That tractor does not have a hydraulic pto clutch. It's mechanical. The only thing I can think of that might cause the pto shaft to slow down is maybe a travel clutch issue, however that would also show slippage while under a load in gear (engine revs, won't hardly move). The PTO "clutch" on those is a pair of "cams" that mesh together. They are steel. The cable actuates a fork which pushes one cam into the other. Generally speaking if one of the cams is rounded off/damaged, or if the spring is broken, you'll almost always get lots of noise. Clacking, hard to engage if at all, etc.

I third the suggestion of looking at the shear bolt. Also if your shredder has a slip clutch, I wonder if the slip clutch may be slipping?

 

[hodge]

Short of exploring the PTO shaft on the mower, you could install another PTO driven implement and see if it functions under load. That would isolate which piece of equipment owns the problem.

 

[BAP]

Take pictures of your PTO shaft of the mower, including each end and post them here so people can see what you have and give you good advice.

 

[ctfjr]

That tractor does not have a hydraulic pto clutch. It's mechanical. . . .

I meant a clutch on the pto shaft for the implement

 

[barkster]

Thanks everyone for the tips. It was a $5.00 fix and I'm back to work.

My bush hog driveline has the slip clutch, which appears to be OK... but the bolt connecting the driveline between the slip clutch and the gear box input was missing. Not certain if the original bolt was Grade 8 or a Grade 2 shear (shouldn't have been a shear bolt per the OM), but I replaced it with Grade 8 anyway.

If it was a grade 8 to beging with, I'm wondering why the slip clutch didnt keep it from snapping. Will have to take a closer look at the slip clutch another day.

 

[lugbolt]

I imagine that the slip clutch ain’t slipping. They’ll do that if the clutch isn’t “slipped” periodically. Supposed to back off the springs and slip the clutch then tighten am back up.

 

[barkster]

I imagine that the slip clutch ain’t slipping. They’ll do that if the clutch isn’t “slipped” periodically. Supposed to back off the springs and slip the clutch then tighten am back up.

I saw the instructions for doing the clutch run-in in the OM. If the clutch isn't slipping and I have to disassemble it for cleaning/repair, is brake cleaner ok to use on the clutch parts?

 

[barkster]

Thanks everyone for the tips. It was a $5.00 fix and I'm back to work.

And that fix lasted all of about 1 day... :-( (ugh!!)

It handled the grassy parts of the field well enough, but as soon as I drove into some brush (no thicker than 1"), the new grade 8 bolt snapped off again. Guess I'm goona have to take look at the slip cluctch sooner than I thought.

 

[Jim L.]

And that fix lasted all of about 1 day... :-( (ugh!!)

It handled the grassy parts of the field well enough, but as soon as I drove into some brush (no thicker than 1"), the new grade 8 bolt snapped off again. Guess I'm goona have to take look at the slip cluctch sooner than I thought.

And also a look at the blade edges, especially toward the tips. If replacing the blades, replace the blade hardware.

 

[Russell King]

And that fix lasted all of about 1 day... :-( (ugh!!)

It handled the grassy parts of the field well enough, but as soon as I drove into some brush (no thicker than 1"), the new grade 8 bolt snapped off again. Guess I'm goona have to take look at the slip cluctch sooner than I thought.

Do you really want to risk damaging your tractor? Just get the slip clutch working properly and adjusted properly and then use the implement as intended.

 

[lugbolt]

yup worn blades will put considerably more force on the pto shaft if an object is struck. also if the bolt hole in either of the pto shafts is egg'd, the bolt won't last long. And, grade 8 bolts don't mean much anymore. Used to, now their tensile can be as low as 8,000 psi. I found this out the hard and expensive way. Camshaft, small block Ford. They only have the single bolt holding the sprocket onto the cam. Ok great, I grabbed a grade 8 bolt and screwed it in. First time to the track, bent all 16 valves. 8 were titanium at about $150 each. Damaged the cam and sprocket too. Grade 8 bolt broke right off, broke the dowel pin and the rest is history. ARP cam bolt from now on, which is 220,000 psi tensile....and you can feel it when you torque it down.

 

[barkster]

Tractor Supply was selling these grade 8 bolts. The spec was 1/2" 13 x 3" with a nylock nut.

It was two of these that broke quickly in light brush. Interestingly, the specified 3" shaft wasn't quite long enough for the Nylock nut to fully engage the threads. When tightened down to correct torque, the tip of the bolt shaft was still recessed maybe a little less than 1/8" inside the nut. Wondering if that contributed to the failures.

So I got these... 1/2" 13 x 3.5" flange bolt and nut, also grade 8.

The extra 1/2" took care of the recessed bolt tip, and with patient progress I've been getting through heavy brush/small trees (under 2") with very little trouble since.

I scribed a mark on the slip clutch this morning and after clearing a patch heavy brush, I can see that it did slip. That's good news. So, I guess it was just a matter of finding the correct bolt. (???)

Thanks for the comments, everyone!