As for the Dodge Ram TCM. Warp2Diesel has a non crd TCM, stock gas Grand Cherokee I think, that he has "trained" to work in his CRD.
Try a search.
I used to tow our 3200# 17' Casita with our CRD a with a Euro TC and the GDE Full Torque tune.
I have two TCM's an original "pre f37" for normal driving and the "Post F37" TCM that I find works well for towing.
Even with the Euro TC using the pre f37 tcm for towing I have gotten shudder once. (forgot to swap to the F37 before that trip)
The original pre f37 TCM will hold 5th gear down to 54 MPG (around 1600 rpms) and applying just a little pressure on the skinny pedal, not enough to down shift I found out what real shudder is

From my experience and what I've read this transmission regardless of tune can not utilize 4th gear enough that is really needed for towing.
It seems to be 5th or 3rd. It's very difficult to keep it in 4th when towing

The "Tow" tune does a good job making the CRD make use of 4th gear. It holds 4th until 68 or 70 ish, then shifts to 5th. Then it will hold fifth down to 50 unless you make it downshift (WOT will do it) and it will downshift into 4th. I really loved the improved shift points on mine. I live in a super hilly area, and the thing always wanting to be in fifth gear was killing me. Then the only choice for downshifting was third, it would hit 3rd, race the engine, I would let off the pedal, and it would immediately shift back to 5th. All the while shooting EGT's through the roof.