use whatever gear the TCM choses...just leave it in D, tow/haul on. The TCM is smarter than us and in 99% of situations, make a better decision on which gear to use! Mines a 5-speed, but ive never had to lock out overdrive when towing or anything...the TCM does a great job with this transmission...its very smart and has a well designed shift algorithm. And from what I understand, the 2006's are even better.
I just hit tow/haul and go. That is what the manual says to do and the dealer. If it can it will slide into 6th just have to wind it up to about 65 to get her to kick in on tow/haul, after that it will purr right along till ya rap it in the ass or hit a hill. Have fun
I towed a 13,000lb 5ver with my LBZ with Boost and EGT guage in tow/haul from NY to Florida and back again. Exhaust temps with cruise on never get above 1250 degrees, so you have nothing to worry about. Put her in drive and enjoy the smooth sailing for a stock truck it is very impressive:ro) Dave
Overall, I have left the rig in tow/haul and let the tranny have it's pick. On one grade I did go to manuel mode since the tranny seemed to be lugging a bit, and dropped to 5th just to bump up the rpms. During this I am pulling a 8,000lb 5th wheel. The manuel mode really is a dream on those nasty downhills, saves riding the brakes by dropping to 5 or 4.
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