transmission temp guage not indicating temp

[sew0177]

A while back both trany temp guages, analog and allison control pad, stopped indicating temp .... the pad doesn't show temp but was showing code 70 which is too low sump temp to show fluid level.

I took it to an allison shop and it worked for them right off. They put it in gear and ran the rpms up to 1200. Then they drove it up the freeway for a while... both worked fine.

I picked it up today and didn't get a temp reading on the analog ...driving 40 miles ave 60 mph. I got to the storage lot and checked the pad...still got code 70.
I then put it in gear and ran the rpm to 1200 and within a couple of minutes the analog started to show temp. I put it in neutral and tried the pad. It was showing code lo- and a flashing 6.

Any suggestions?

[sew0177]

The only thing I can think of is while running it in gear, the fluid is getting hotter than actually running down the road. The temp sensor could be just going bad to the point of not registering until the fluid is really hot.