2004 drw 6.0 tran temp problem

I have a 2004 F350 DRW 6.0 with an automatic transmission. The Trans temp gauge is working only intermittently and when it quits, the check gauge light comes on and the tow haul light blinks. It only does it when the tranny warms up and seems to reset after it cools. I am thinking bad tranny temp sensor but am looking for an expert opinion before I just change it.

Upgrades to the truck include Diablo tuner, EGR blocked off and 4" no cat/muffler exhaust.

Any help is appreciated!

the stock trans temp guage is nothing more then a gloifyed idiot light, get a scanguage or a set of guages to see if the trans is overheating or not

A little more on this....
Yesterday the tranny acted like it didn't want to upshift from 3rd to 4th and then to OD. It tried to run 3200 at 50 mph. It eventually shifted normally and I haven't had the same problem since but the temp guage and tow haul lights are still active.

Mustangman,
I did run an OBD scan but had no high tran temp readings. I got an "unknown" code of 1334 if anyone can help with that.

if trans is overheating you have a blockage in the transmission cooler, if not overheating the trans temp sensor inside the pan is messed up, pretty common problem.