shuttle shift at high rpm

[Anonymous Poster]

Well, after putting about 180 hrs on my L3600 GST, it has come to my attention that I may have been abusing my tractor. The owners manual states- "reduce engine speed to low idle before shifting the shuttle shift lever". While bushhoging, I shuttle frequently at opperating speed (2500 rpm), always being careful to come to a complete stop before shifting. The tractor doesn't seem to mind. I really don't see a practical alternative to this method, except controling engine rpm with the foot throttle, which I could do if necessary. Your thoughts/ comments would be appreciated.

Jeff

 

[geneP]

Jeff,

While the owners manual for my L2250 does not give this instruction, I have also shifted between forward and reverse with the engine at PTO speeds quite easily. I have noticed, however, if I put the shuttle lever in neutral and release the clutch while the engine is at higher rpm, It will tend to "grind" when I return to forward or reverse without reducing the engine speed. To help train myself, I try to return the engine to idle when I place the shuttle in neutral. It is then ready to shift into gear when I am ready to move the tractor again.

 

[Kubota-monkey]

The Manual for my L35 Gst says you dont have to pull into neutral or stop to shift... Arent GST's shift on the fly?? And i cant imagine that high Rpm would ruin a transmission or the sort while shifting.

 

[geneP]

Ooops!! I didn't read his post closely..The transmission in my L2250 is a mechanical shuttle, not Glideshift

Gene

 

[_RaT_]

Gene, I use the shuttleshift as you use it. I have no problems with gears meshing so the transmission will be fine. A good reason for reducing RPM's is to avoid clutch wear. The clutch on the L4850 I use is in an oil bath. Since it is immersed in oil (many fork lifts employ wet clutches) I feel the heat being generated will be minimal. I certainly would not be concerned with the transmission, just go easy on the clutch, if shifting to a lower gear or higher gear, you should not have any extraordinary clutch wear. When going from forward to reverse, allow the tractor to come to rest on its own or via the brakes, making the clutch/shuttleshift stop and reverse directions would certainly result in premature wear. HST eliminates the whole clutch problem, one more reason my next tractor will be HST. Rat...

 

[TomG]

Like another post, I wonder if the recommendation has more to do with the clutch than the transmission. Modern synchromesh transmissions solved the problem of differences in input and output transmission shaft speeds when shifting. That was the original reason for 'double-clutching.' Besides, if it's a transmission issue, it's better to increase engine RPM (while going through neutral) when shifting down and reduce it when shifting up. Some transport tractor drivers say it's better to shift without using the clutch at all.

I think that if the tractor is stopped or slow, and shifted to a high gear, the engine governor will attempt to maintain engine rpm and the tractor will accelerate to speed in a short time. The clutch has to do a lot of work during the acceleration.

Another thought: When a rotary cutter is attached to the PTO, changing engine speed, even when stopped probably adds to clutch wear. There's a lot of inertia in cutter blades, and the clutch has to absorb the energy in any change in inertia. A PTO over-speed clutch may absorb the energy in going to a lower RPM, but not to a higher one.

 

[Kubota-monkey]

Gene I made the same mistake...

 

[rbargeron]

Two more cents worth.... I think the warning about reducing engine rpm before shuttle-shifting is to keep big torque impulses from tearing up your machine, also has to do with operator saftey - keeping from collecting the steering wheel in the face if you pop into reverse at speed.
The important point is not engine rpm - but wheel speed (what gear you're in). I find I can bat the shuttle anytime in 3rd (of 8) regardless of high engine speed. But in 4th or above, abrupt reversing is harder on everything.

 

[Kubotaman]

It won't hurt too much in low gear ranges, but it will start wearing cluthes hard in hight gear ranges. Eventually you may need to have the heavy duty clutch kit installed. We have had to do that with about 3 of our customers tractors that "abuse" the shuttle.

What I would do is if you are chopping liek PTO usage, set throttle at about 1500 and use foot throttle. Set a stop on foot throttle not to go over Pto rated RPM too far.

 

[Alan W.]

They will mess up at least mine is going that way, and yes my crew shifts the shuttle at pto speed, but only in the lower three gears. Check out my post GST Shuttle.