Yep, an EB is really worth having, especially when you tow or haul.
But: It is an extremely bad idea to just install one (about 700-100 US$ AFAIK
) and then not to adapt your automatic transmission correctly.
OK, this costs another bundle, but it will avoid you having the tranny give up right in the middle of a descent and free-wheeling down the mountain and then having to order a tow truck.
The system I meant was really rather primitive, it was a small pneumatic cylinder that pushed the throttle valve lever on the tranny in the same direction it is pulled when you step on the go pedal.
The tranny uses this information to regulate itself to cope with the torque the engine delivers- low throttle low torque, open throttle high torque. The tranny does not care in which direction the torque is applied. (power or braking).
(I have built such a "thing" with parts sourced locally for a friend who tows his excavator over here in the alps- I just teed it into the air line that activates the exhaust brake- which came from a scrapyard and fit right into the 4" exhaust)