towing down steep hills
I agree with the previous post, except that the max RPM of the V-10 is quite a bit higher than that. The max torque for that engine is 4600 so you are safe to go some above that. But, I also keep my RPM below 4500 by using the brake as needed.
If a down slope is long and you do not use the engine and transmission to hold you back you will likely over heat your brakes and could cause several different problems, any of which could lead to brake failure.