High trans temp on M944A1 - M939 chassis - after short drive

Ok, we took the M944A1 our Friday (been sitting about one year) and ran the generator for awhile and the big cooling fan kicked on a couple times. Then we noticed the transmission temperature gauge was pinned at 325!

Today (Sunday) we took it out for a drive and same transmission temp reading. So we shut it down and now are looking for answers.

Can anyone suggest a path to find the issue? We'll be working it Monday AM.

1. Gauge check
2. Sender check
3. ??

Same sender as coolant, if you can put your hand on the trans. pan, it's not too hot. Check it with a I/R gun or camera and see where you are at or swap trans. senders / gauge wires with coolant sender / gauge.

Ok, we measured voltage to the sender on the trans - it was 24 volts, voltage to water temp sender was 15.6. So either they are different senders or there is a wiring issue.

I'll get the IR gun - good idea. Hands can be put on trans when hot but just for short time. After several tries the trans temp gauge pings the needle - so suspect sensor or gauge failure and not an overheating problem. Will try the IR to verify.

Location of the transmission sending unit for the m939?

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TEAMJENSEN said:

Location of the transmission sending unit for the m939?

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Click to expand...

Top of the transmission. Where the cooler line returns to the transmission

Simp5782 thank you! I was able to find with your help the sending unit and now have the transmission temp reading correctly. I appreciate the help and the picture was very helpful.

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is there way to repair the sender what is a replacement part number? my gauge just keeps climbing up till max But the IR gun reads 170-180 on the pan about 185 on the filter so its definitely not overheating.