Hurth ZF two speed transmission

[clay]

Does anyone have any first hand knowledge of the Hurth ZF two speed transmissions?

I am looking at a B31 equiped with 300 hp cummins and ZF 90 two speed trasmissions, guy says they are rated to max of 320 hp at 2800 rpm he says that they are great fuel savers if you are making long runs - They have electric shift gear ratio change from 2.03 to 1.58 and some sort of override sensor so you can't down shift at high rpm.

Clay

[Eddy G]

Clay: I would be interested to know how two speed transmissions can be better on fuel than conventional ones. We have to gear and prop our diesels to turn a minimum rpm at full load and WOT, so I assume the "high gear" on the two speed is set the same. If not, an overload situation would occur and lessen the life of the engine. The only advantage I can see is the ability to troll at slower speeds and more manageable docking in the "low gear" mode. Help me understand.

Eddy G.