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s300 bobcat surges in 2nd gear

Discussion in 'Heavy Equipment' started by rich414, Nov 19, 2011.

  1. rich414

    rich414 Senior Member
    Messages: 294

    I have a 2008 s300 bobcat 1600hrs on the unit ,high flow, gold package, turbo'd , 2 speed. When in 2nd speed going up a slight grade 1-2% with VTS tracks on or a steeper grade with tires on the machine surges, kind of like lunges. The hand throttle pinned at 2450 rpms, you can give it 100% joystick forward or 20% joystick forward and the units drive system surges. If the hand throttle is at 2200rpm or less, and you give it 100% joystick forward the problem doesn’t exist. This happens when the outside temp is -10 degrees to 110degrees.
    With snow approaching I have got to get this resolved.
    I have changed the hydraulic cone filters, located above the rear chain case inspection plate and rear left side inspection cover. NO luck.
    Changed fuel filter No luck
    Next is change the fuel pump but that is $150
    Is this problem with the motor, fuel system or hydraulic system?
    Anyone out there have a solution or thing to try replace???
  2. rich414

    rich414 Senior Member
    Messages: 294

    here is what the BOBCAT REP told the local dealer to tell me....
    Try running the machine in snail mode and ramp the speed up to 99. If the problem is gone then it is the engine speed sensor. The speed sensor could be bad, it needs the software updated, or both. In normal drive mode it monitors the engine speed. If the joystick lever stays in one position and it sees the engine rpm drop it backs off the hydrostatic pump. If the engine speed sensor shows a false speed change you can get a surge induced. When running it in snail 99 it no longer reacts to the engine speed signal so this will tell you if this is what is happening.

    Here is the results and questions to the above suggestion
    In 1st speed, in the complete hand throttle range idle to full throttle NO surging
    In snail speed 0 to 99 no surging
    In second speed idle to approx. 2100-2200 NO surging, above that surging
    When in snail 99 and I change to 1st speed, the speed stays exactly the same so how can the “snail” mode have anything to do with 2nd speed?