L3710 PTO spins, but no torque

[PTO'd]

After fixing MMM gearbox leaks, & putting back on L3710 tractor, I mowed about 10 feet of grass & PTO just stops. Didn't notice any thuds/sounds nor oil puddles. Deck belt spindles move freely, but mid-PTO would not turn them, just kinda try & "jerk" a little every few seconds. So i watched the rear PTO simultaneously & it still moves, but would hesitate/stop every 5 seconds. So I did a really dumb thing & put a pair of pliers on it while it was spinning to see if I could stop/hold it (PS. Don't try this at home, I am a paid professional idiot)..... & sure enough, I could stop & hold with the pliers.... so even though rear PTO will spin... it has NO TORQUE whatsoever. At low RPM's, while holding pliers, I can feel the PTO trying to turn/hit about 3x/per second or so, & each "hit" gets stronger until about 10 sec's later, then kinda repeats itself (almost like building up pressure). Can only notice this behaviour at low RPM's,.... as increase engine speed, then more torque is applied to PTO, but can still hold with pliers. (yup, I ate my spinach this morning). I'm somewhat mechanically inclined & will fix myself (out of cost necessity), just a little new to tractors. Any ideas/help?

Other notes.... tractor = L3710 HST with 757 hrs & 72inch MMM (belly mower). It is a used tractor I bought last fall ~ 6 months ago, only have put 5 hours on it since then.
Clutch pedal seems OK, though doesnt disengage clutch until close to bottom 20% or so of pedal to floor. The mid-PTO selection lever has always been kinda tight/hard to engage (mind you, I've only used it 5 hrs so far), but now the mid-PTO is near impossible to move to the engaged position. I'm thinking maybe some "PTO clutch" or something (from reading through other posts). Also, did really dumb thing of "jump starting" in the dark & sure enough (red looked black to me & SPARK-SPARK... had the cables reversed for 5 sec's or so. I'm sure it messed some things up (key wont shut it off now, have to choke it to die),... but dont think this would affect PTO clutch internally,... or would it?

Not afraid to tear it apart to fix (can't afford to pay a dealer that kinda money right now). But just need to know what to look for being broken or something, since I wouldn't know what/where to look at to begin with.

Thanks in advance for any/all help suggestions!

 

[KennyV]

I see this is your first post… Welcome to the fray… lots of information here, some of it good.
You did not say but has the pto ever worked for you?? The selector may not be adjusted correct to allow engaging the PTO, give that a look… also the red knob you pulled to stop it is not a choke, that’s the manual fuel shut off. Check your fuse panel, you probably have an open fuse, that’s why the key no longer cuts off fuel… good luck and post back, KennyV.

 

[5030]

On a 3710 there is only 2 things it can be. Either the pto clutch cable isn't adjusted correctly (which is what you better hope it is) or the pto internal over running clutch is shot. The mid and rear pto on a 3710 use the same over running clutch pack. It's a hydraulic pack in the rear case that allows the pto to free wheel for implements that hold their shaft speed after the engine is throttled down, i.e.; brush hog. However, the jerk you describe is associated to the clutch engagement cable being out of adjustment.

If you can't afford a dealer, I'd suggest getting a Factory Shop Manual. The 3710 Owners manual tells very little about the internal workings and there is a lot of stuff in there.

 

[PTO'd]

Thanks for replies --- great help so far!

CLUTCH CABLE ADJUSTMENT = bottom of cable (by midcase) was already adjusted as long ("tight") as would go. Top of cable (right-side of seat) had lots of room for lengthening ("tightening"). So tightened it, but to no avail! Had it so tight the PTO stayed engaged/spinning even when lever in "OFF" position, but still no torque (can still hold with a pliers). So, I adjusted cable back to where it should be (on/off with lever).

The mid-PTO will turn on/off with lever OK I guess, kinda ruff/hard/tight,... but a good jerk is getting it to turn on. I noticed the rear PTO will spin most of the time (& stop/hestitate every 5 sec's) when engaged by itself. When I turn on the mid-PTO also, they both get kinda nosiy & will hardly spin at all. But this could be solely attributed to more gears/load on an already bad PTO clutch. (The mid-PTO can only be engaged once the rear is already running = just the way the L3710 is made I guess.)

Called a dealer, parts were only ~ $110 for 2 PTO clutch cams (TA040-23410 & TA040-23450) & spring (TA240-51470). (Shop manual $100, but oh well, gotta have it!). He stated that should be it, as long as no gears are busted! -- I wouldn't think there would be any chance any gears could be busted since the PTO spins, ... correct? He said to pull the PTO shaft out of the rear-end & could fix/replace all the parts that way. Is it really that "simple"? I guess I need to drain all my hydr-tansm. UDT fluid first then?

And, while I'm in there, any other parts/bearings/.... I should replace?

OTHER NOTES = The main clutch seems fine. It will start/stop PTO & HST transmission just fine like a should (I cant imagine the main clutch going out any time soon on an HST model). The PTO's have worked before. I have mowed my yard once, & about 3 acres out back. But the 3 acres were kinda tall ~ 3-4ft in places, & the blades on the deck turned out to be in sad shape = way past dull. While I was mowing before, the blades would slow down in some tall spots while turning,... so in hindsight, I probably got a tractor with a PTO clutch that was pretty bad & when I tried mowing 3-4ft weeds with dull blades... I just finished burning the rest of it up! Live-n-learn!

Is it "safe" to yank the PTO shaft out of the rear-end & look for bad gears... before I can get a shop manual shipped to me?

Thanks again for replies!