Tranny shops and certified Tranny mechanics will tell you that the excess heat generated by using the tranny to hold back your speed will have long term, excess heat generated problems.
Why chance it.
As for driving down the I-70, I do it all the time running between 60 and 70 MPH with ne need to use the gears or brakes. Actually, I know very few, if any Rover owners that use their tranny for their high speed braking.

 

on a disco i wouldnt do it. however with the 6hp26 in luxurys 07 its fine. youre actually letting it cool down some by downshifting. the bigest cause of heat in the tranny is from the torque conv, when it shears, you get a lot of heat. the 4 speed zf is on or off, based on what speed youre travelling. the 6spd will vary the tcc lock up and when you downshift and are over driving the engine it will be fully locked. in the end, youre putting more strain on the engine then the tranny by doing this, but as long as youre not goin from 5th the 2nd at 35mph or anything like that, youll be fine. the tranny has special shift maps for downshifting like this

 

Luxury1 I attempted to send you a message and it said you weren't receiving them?

 

Hi Mlshelton, I had it disabled but just enabled it.