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catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 2243
Experience:  Field service technician for CAT 19 years.
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I have a cat d4g XL its been sitting up few months so when I

Customer Question

I have a cat d4g XL its been sitting up for a few months so when I went move it the transmission would drop out of third gear to first. If I shut it off I could move the transmission back to third but as soon as I applied power it would drop down to first again. I let the dozen warm up for about 45 mins then drove it around for 10 mins or so thinking it just needed to warm up. No luck. The transmission temp got up to about 120 degrees F, but didn't get much higher in the hour I had it running. Thoughts?
Submitted: 10 months ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 10 months ago.

Hello,

The most common issue I find is the throttle cable has stretched.

Pull the hand throttle to full speed and then check the lever on the injection pump to see if it is pulled tight to the stop.

If it is not, try adjusting the cable. If the cable is stiff or damaged in any way, replace it and set the new cable to pull the throttle to full speed.

If the problem is still present, you may need the dealer to calibrate the transmission drive system for full performance.

You cannot have any warning lights on when this procedure is performed. All system faults must be fixed before calibration will begin.

Customer: replied 10 months ago.
is there some relationship between the throttle position and the functioning of the transmission? While I am certainly no expert on this, it seems odd that the position of the hand throttle and the position of the throttle at the injectors would cause the transmission to fall out. I will say, that the engine seems to do exactly what I am asking of it when when I apply throttle. There are no indications of any faults present. Is it possible the hydraulics could have been overfilled at some point causing a pressure lock? I should say when I parked the dozer a couple of months ago it was functioning fine.
Expert:  catmastertech replied 10 months ago.

No, oil level will not affect the control system.

However, engine RPM is monitored by the ECM and if it does not see full throttle, it will slow the pump output. It is assuming you are climbing a grade and engine speed has reduced so, it reduces pump output.

It is weird but, I have seen this several times. If the speed signal is not where the ECM thinks it should be, it will reduce output or log an error and then turn on the transmission electronic warning light. Since you did not report any lights, I must assume the engine speed is too low.

Customer: replied 10 months ago.
Ok, I will test out the throttle theory this afternoon and report back.
Customer: replied 10 months ago.
Unfortunately the throttle cable is fine. It hits the stops in both directions. I saw on a blog where this same issue was discussed and they said something about a recall on the bow tie switches in the joystick and a screw in there falling out. I sort of doubt that's happening here because if I shut the dozer off and restart it I can move the speed selector back to the top. As soon as I get moving it falls to the bottom again. Still no warning lights illuminating. I took a video of it with my phone I could probably email if that would help, but honestly it will just show what I am describing. It seems like this may be more common than I thought.
Expert:  catmastertech replied 10 months ago.

Yes, the last one I heard with this issue had speed sensor issues and needed a full system calibration performed before the speed would return to the correct operation.

The speed sensor design has been upgraded and unfortunately, the calibration process must be done with CAT ET. Very few independent mechanics have this. Usually you must see the dealer to get this procedure performed.

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