766 stalls when turned sharp left?

100hp766 · Jan 31, 2009

I have a 766 with loader and when I turn sharply to the left it will stall momentarily, like no power to right wheel. Otherwise it works just fine, no noise in rearend, pulls hills fine. Any idea where to start looking or possible cost of repair? IH shop man says spider gears $4000. An IH mechanic says MCV valve rebuild. What do you all suppose it could be?

Owen Aaland · Jan 31, 2009

The most likely cause is a worn out MCV pump. Turning all the way to end of steering travel will cause the the steering hydraulic system to go to maximum pressure. If the pump is weak it will not be able to supply enough pressure to open the steering relief valve. This will cause a lack of pressure to the brakes and TA. If the TA is in the forward position the high side clutch pack will release causing the TA to pull only on the low side sprague clutch resulting in a momentary loss of power to the wheels.

A bad side effect of a worn MCV pump is loss of lube to the differential and range transmission main shaft. Excess flow from the MCV pump is used used to lubricate those parts and since the steering has priority for the oil flow, the differential can be starved for lube even if the steering still works OK. That is why it is important to replace the MCV pump when steering/TA problems first start showing up at low idle. Almost all of the differential failures I have worked on could be traced back to problems with the MCV pump and lack of lube.

766 stalls when turned sharp left?

100hp766

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Owen Aaland

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