The owners manual says to "Engage the PTO at reduced engine speed to avoid shock loads to the PTO". It does not define what "reduced" is so the wording definitely leaves some room for interpretation.
BTW, I know the noise is not coming from my rotary mower blades or gear box. The noise definitely emanates from below the drivers seat somewhere in the driveline.
Could anyone with a later model
L3400 or L3700 that either does or has engaged their PTO at idle speed tell me if they get the same clatter/rattle/knock that smoothes out at RPM's increase?
thanks,
Steven
In general, I try to engage the PTO at the lowest speed that the engine won't stall, and that varies from one implement to another depending on the amount of inertia they have. My rotary cutter and drivetrain is noisy (Land Pride 1860) at idle. The PTO power pulses aren't smooth enough at idle for smooth operation, until you get up to about 1100-1300 rpm when things even out. Essentially what is happening is the engine is trying to spin the cutter, then the cutter is trying to spin the engine. I can engage it at idle if I'm careful with the clutch, but I probably bump it up 100 rpm or so before engaging.
The post hole auger is smooth as silk when engaging, even at idle, it has much less inertia to overcome. Also, it has an under-driven gearbox, output speed is less than input. The rotary cutter is over-driven, the output speed is greater than the input.
As for engaging the PTO at full PTO rpm, that's the same as engaging the transmission in your car at the engine rpm you normally drive on the highway. Very hard on clutches and driveline, and something I personally would not recommend. You're asking the cutter, which has considerable inertia, to instantly spin up to full speed. A hydraulic drive can cope with that to a certain degree, but a friction clutch isn't going to do well long-term under those conditions.
If yours is an HST, I'd recommend engaging the PTO at just above idle, enough that the engine won't stall, then ramp it up gradually to full speed or wherever you plan to operate it. I run my rotary cutter anywhere from 2000 to 2400 engine rpm. I have an
L3400 DT (gear drive). I suspect your PTO 540 on the L3700 equates to about 2350 engine rpm?
Not sure if the HST model has a foot throttle or not, if it does I'd recommend using it to get the mower turning. The hand throttle is a bit clumsy in comparison, but works ok once you're rolling along.
As to whether you have a problem (defect) or not, it's possible. It's hard to tell without actually hearing or feeling it, the dealer may be your best resource for peace of mind. Protect that warranty just in case you need it !
My 2 cents,
Sean
