I have a 2001 Dodge 3500 with a 24 valve cummins. The o/d off light came on and kicked it down to fourth, then the transmission temp light came on. Took it to a mechanic and he replaced all the clutches in it and done some other things. Not exactly sure what it's called but I think it was a TCP valve he replaced. Torque converter, I think. Anyway, I get it back and am headed home when the o/d off light came back on along with the trans temp. I take it back and he replaces something that goes to the trans oil cooler. Get in it again and same thing, so I had a diagnostic test run on it and it gave me a code P1973. The man that worked on it says he's sure the oil cooler (which is beside the radiator) isn't working because it should be hot when you touch it. Which is true, it's not. But still, shouldn't that code mean something? What do you think?

When there's internal transmission damage, the transmission coolers (radiator and supplemental cooler) can become plugged. I would definitely check that out.

I'm not sure what DTC P1973 is.