TW 35 Pressure Testing Hydrulic System Questions

I posted about 2 weeks ago about my TW35 slipping and found out the clutch was the cause. Now there is another problem. When the engine is idled down the hyd pressure light comes on and the dual power slips. I carried it back to the dealer and we went through the pressure checks as outlined in the manual. Here are the results: I have 2200# at the remotes. Next was the dual power test. We had 210# each time we tested. Dual power shift high to low, pto on off, differential lock, left brake, hold left brake push right brake. Next was the low pressure test. When we put the gauge on the lower line of the oil cooler, we had 0# at 1200 rpm. Manual says it maybe the relief/regulating valve or a blocked oil cooler. When I left, the mechanic was removing the valve. My question is, if this is not the cause, how do we check the piggy back pump on the back of the transmission? I am suspecting this because the tractor has to be split to replace it. Thanks, long post!
 
Update from the dealer. They found a broken copper shim in one of the spools. Replacing it and cleaning valve and see what happens!
 
These valves were never shimmed from the factory, and if they were, they wouldn't have been copper. Someone has been monkeying around in there before and I suspect trying to compensate for a problem elsewhere. Earlier valves were sometimes plagued by contamination plugging the orifice inside the spools.

That said, the transmission pumps on the later TWs were not known for issues (earlier TW tractors, such as the 10, 20, & 30 suffered from a low capacity bearing). Pump can be flow tested by removing the regulating valve and bolting a flange adapter in its place. I have one that I custom built just for that purpose.
 
If the shim was added to compensate a problem else where, where would you suggest we look? Also, the brakes seem to not release on this tractor. I don't know if this means anything but thought I would throw that in. Thanks!!
 
There is pressure going to the low pressure regulating valve but none going out. The mechanic thinks its a bad valve. They are no longer available. Figures
 
The dealer took the valve apart and as mentioned before, found a broken copper shim. They also found the lubricating spool in backwards according to the manual. They corrected all this and still have no pressure on the other side of the valve. Here are the pressure readings: 210# into the valve, at 1000rpm no pressure, at 2200 rpm they have 50# pressure. They have torn the valve apart 2 times and cleaned it with no results. Is it possible this valve is bad? Thanks
 
Does the guy who's working on it have a hydraulic schematic for it? If he does, he will notice that the brakes have priority in that system. Since you said the brakes appeared to be sticking, that might be a clue. Maybe try temporarily capping them off and seeing what kind of pressure you get.

If you suspect a pump issue, attached is a picture of a test fitting I made to do a direct pressure and flow test on a TW transmission pump.
a265258.jpg
 
Well, Bern, third time's the charm. They decided to tear down the valve again and reclean it. They polished the spools to make sure they had no burrs on them. They put it back together just like the manual says and it worked!! Needless to say they were very, very, happy! Yes, they had the Ford shop manual. Tanks Bern for your time and knowledge. I always read your replies no matter what the topic. And I must say I have never found you wrong on any repair.
 

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