I agree with all of the above. I am having my trans rebuilt right now. And I have been able to watch all the parts as they come out. The O/D looked good, you could actually still read the print on the clutches. But I had burned out the 2nd and 3rd clutches, which at 126,00o on the clock, I think that's good.
Well any way, the discussion came up about towing in O/D he said that it's not a good idea if your tranny keeps hunting for the right gear. Being that my rig with the 5th wheel is about 22,000 pounds, the hunting is often.
Of course I am getting all the upgrades for the trans, and he said I can tow in over drive with what I am getting. BUT, he also said that if you do, always downshift (turn off O/D) before you start to go down the other side.
So, I still think I am going to do it the old way. Since there is no reason to go 75MPH with the 5er in the hills, down shifting wont be a problem.
Also, I have the late E4OD, which I told was made in 98. Which from everything that I have seen at his shop, it is almost like the 4R100. And my rear axel is 4.10, that helps.