Max RPM

[firedreamer]

Can someone tell me what the max rpm's I should keep my 2005 3500 crew cab, LB, DRW 6.6 LLY / Allison 1000 at while towing a 5th wheel on the downhill's ?

[DmaxMaverick]

The stock programming allows operating in two redline maximums, and the stock programming won't let the engine exceed either (it will either defuel or upshift). Earlier models actually had redline hash marks on the tachometer, while later models do not (simply not needed). The maximum on compression (downhill) is 4500-4800 RPM, which is completely safe. I don't know what it would do if you run up against that in top gear, but I wouldn't be worried much about engine RPM at that point. It will not allow any fuel if the load/throttle maximum RPM is met or exceeded.