Cat 980H JMS21?? transmission problem

[Chisumtrail]

Got called out on a 980H JMS21?? when transmission gets hot it does not want to shift into reverse sometimes. Checked codes with ET, no transmission codes, checked transmission pressures all at same time, solenoids were not sticking. Going back in the morning to cut filter, check screen, drain oil. Any ideas?

 

[Lee-online]

Performing the clutch fill calibration is a good troubleshooting because if it fails it will give a code and reason.

F&R switch working ok? Does it show R on the dash. Does it feel like it tries to go into R.

Data logging all the trans parameters will show what is going on.

 

[Chisumtrail]

F-N-R is changing. After I drain the oil and see if anything falls out i'll try that.
Thanks

 

[Lee-online]

If its only doing it in reverse and only when hot, it would lead me to clutch #1. Either the clutch, solenoid or possibly the wiring. Cut the filter to see if it is full of clutch material but draining the oil prolly wont show much.

Swap the solenoid with #2 and see if the problem jumps with it.

 

[ben46a]

You didn't happen to just buy it did you? Out of curiousity. We had a jms21?? And traded it for that issue, and I know it went stateside.

 

[Per Eriksson]

I'd swap the solenoid just as a quick way to rule it out anyways.
Have had that happen before that they sometimes act up without you being able to catch it on gauges or ET.

 

[Bob/Ont]

Giving trouble when warmed up usually means a leak. Clutch fill will find that. But it could still wiring if the solinoids and connecting wires are covered with dirt and roasted.
Later Bob

 

[Per Eriksson]

I've found that the clutch giving problems first is usually for second gear, the one inside the other that's fed through the axle, the seals against the axle seem to evaporize into thin air, several times I've taken them apart and not found more than what looked like specks of dirt where they should be.

 

[Chisumtrail]

Thanks for replies, rechecked pressures with different gauges and #2 was not coming all the way down. Changed today. Do you professional mechanics like the digital test gauges or the regular test gauges?

 

[Lee-online]

Both, it depends what i am doing. The mechanical are nice because they show how the pressure is responding. Is the needle moving slow, erratic or fluttering. These can't be seen on the digital but the digital are nice for the high pressures and checking differential pressure. The digital is also safer by keeping the pressure out of your hand.

 

[Lee-online]

Oh, the mechanical are only $35 but the transducers are $200. I have spun both and would rather throw away a gage than a transducer.