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jdemaris
03-23-2006 05:50:41
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Re: JD1010 drives forward in 1st only rev all s in reply to mborrasca, 03-22-2006 13:59:02
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The reverser clutch packs work off of pressure. That maximum pressure is determined by one valve for both forward and reverse. At least 120 PSI is needed to engage the clutches properly - and can be set as high as 150 PSI. That is why, the first thing to do is install a gauge, and see if the pressure stays the same when you shift from forward to reverse. If reverse has the proper pressure, and forward does not - it is likely there is an internal leak. Sometimes, if it is a small leak, you can get around it by increasing the flow of oil by opening the rate-of-shift jet - which is easily done with a screwdriver. Pressure oil comes from the pump, and has to pass through two operator controlled valves - one is a spool valve operated by the clutch pedal, and another is a rotary valve operated by the forward-reverse lever, and into a 3 78" stroke spring-loaded accumulator that softens shifts, and through an adjustable orifice. There is a spring-loaded,shim adjusted relief valve that determines the maximum clutch operating pressure. The route to the clutch packs differs from forward or reverse. Subsequently, something as simple as a stretched clutch-pedal return sping can cause forward to slip and reverse not to slip. Also, inside the control valve assembly, is a cast-iron shift fork that often gets worn. I am oversimplifying the operation here. Nine out of ten times, the problem will be internal, not external. The entire hydraulic control valve assembly can be removed without taking out the reverser - but there is usually little to be gain from it. The best course of action is - #1 check clutch pressure while in forward and reverse with engine at half throttle. #2 Check for full travel of the clutch-pedal spool valve - it can lose travel from dirt and/or a stretched spring. If the rotary valve is not engaging all the way (the forward-reverse shifter), the machine will not slip - it will either allow full pressure, or no pressure. If, while in forward, the machine feels like it's trying to move, i.e. slipping, the clutches will eventually burn up and melt. Then the machine will get stuck in forward, and have no neutral, and stall in reverse. If you find out that there is adequate clutch pressure in forward and reverse - it is possible that the dry engine clutch is slipping, or the steering clutches, or both. Seems unlikely though that they'd only slip in forward.
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