I am changing out my 9 speed Rockwell for an Allison HT 740. With the Series 60 in my Freightliner FLD 120, it will do a perfect job even pulling my 10K trailer, total truck and trailer grossing at 40K lbs.
I had Allison run a SCAAN using either the 4 speed or 5 speed (HT 750CR) and the 4 speed worked out better for highway use. I am changing the rear end from a 3.91 to a 2.80 ratio to compensate for the lack of overdrive. This was also figured into the SCAAN.
Apart from my back not liking the extra heavy clutch in my trcuk, my wife is not a happy camper with the thought of driving it. That's not to say she won't, she would prefer to drive the auto. I would have loved to instal a World but they are hard to find and very expensive when you do find one. That's not including all the electronics that have to go with it and which have to be adapted to fit my 1994 truck.
Peter.
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