Re: 706 stops when you turn too far either way! Any Suggest

Posted by Owen Aaland on September 25, 2011 at 15:25:04 from (216.47.32.147):

In Reply to: 706 stops when you turn too far either way! Any Suggesti... posted by IowaWill on September 25, 2011 at 14:22:49:

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This is a classic example of what happens with a worn out MCV pump and a TA that has a worn out sprag clutch in the low side of the TA.

The MCV pump provides oil for the steering, brakes, TA, and TA and transmission lube, in that order. With no demand on the steering the oil just flows through and the pressure is regulated by the pressure regulator valve in the MCV to about 250 PSI. When the steering is put on demand the pressure rises until the tractor steers or it open the steering relief valve at 1800 - 2100 PSI. In a worn out pump the flow drops off as the pressure increases. When the flow drops off the TA no longer has pressure to keep the clutches engaged and so they release. If the sprag was good on the low side the tractor would down shift to the TA speed but keep pulling. Because it stops we can determine that the sprag is slipping. When the pressure requirements for the steering drop off the TA again receives oil and the clutches engage again with a bang.

When you pull the MCV off the center section you may find a blown O-ring or it is possible that the flow divider valve is stuck but those conditions can be seen after things are apart. If other problems are found it is possible that the pump may be OK.

A bigger problem can not be seen when you have these conditions. The excess flow from the MCV pump is used to lubricate the range transmission and differential bearings. Since the steering has priority if you do not have enough pressure to satisfy the steering there is no lube flow through the oil cooler and the rear frame.

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