I posted this thread in wheel loader but no body commented on it so I will try here. I replaced the transmission pump on 988H with 20000 hours on it because it was leaking. Now it will loose certain gears as it heats up and if you don't start out going in reverse I would go into reverse. Now if you shut. Down the machine for 5 minutes or so you will get some of your gears back for a time can anyone help me out trying to figure this out please? Thank you
This all started after you replaced the pump ? Have you put a gauge on the pump to watch the pressures when this happens ? Sounds like its sucking air on the suction side of the pump
Yes and I checked pressures yesterday they are within spec but I was stationary because my forman said moving wouldn't make a difference in the pump pressure. And how do I check to see if its sucking air?
I believe you said you had ET on it in the first post about this correct ? So no codes? Solenoids engaging (they have current) in ET when different gears selected ? The machine shows that its in gear or does it show N when it acts up ? As the sucking air you should hear the pump whining if its sucking air. Check the pipes from trans case up to the pump very closely. Ensure all clamps are in place and tight. ( I dont have SIS in front of me so I'm guessing at the pump suction pipe and clamps but I'm sure there must be some). The oil in the slight glass should look foamy if its sucking enough air to make it stop. Whats the torque convertor outlet pressure ? Can you check clutch pressures ?
There are no active codes the trans speed sensor 2 had a recent fault history the machine only ran for 3 hours before it stopped working and that's when it through that code but when I got to it it wasn't active I trouble shot it and it was bad but according to the troubleshooting steps that should not cause it to go out of gear. And the machine says its in gear when you select it even if its not moving the transmission oil doesn't seem foamy I will have to check though and how do I check curents with et? I was messing with the live graphing that showed current but I couldnt tell what it meant
I don't have access to a gauge untill later my shop forman is heading up here to take a look at it hes got all the gauges but I am trying to just make sure I haven't missed anything or that I checked everything I could have
You need to be checking the individual clutch pressures at the test points on the modulation valves. I'm going to make a wild unfounded prediction that when you changed the pump you got some dirt in the system. The modulation valves are not at all tolerant of any contamination and are almost impossible to clean out. Have you looked at the filter? If this turns out to not be the case, I apologise in advance.