[Cliff R]

About 6 years ago I borrowed a new (at that time) GMC 2500 HD truck (single cab) with the 6.0 liter engine to make a trip to Florida to pick up a Harley Davidson Road King I purchased. We hooked a small 12' trailer to it for the trip. The truck was fantastic on flat ground and the engine stayed in 6th gear and converter locked up at any highway speed.

As soon as we got on I-77 South and hit some small grades it started downshifting at the slightest load and engine revving up to 5000rpms and staying there till we topped the hill. As we ventured further down 77 the hills got bigger in West VA and the truck was spending nearly all of it's time at 5000rpm's seeking lower gears to keep it there and this is with an EMPTY trailer probably no more than 1500lbs. Even with that little tiny trailer on steeper pulls it wouldn't maintain 70mph either and just kept down-shifting and staying at 5000rpms......I thought a few times it was going to EXPLODE!

At the first fuel up we put in around 30 gallons and had only logged 150 miles or so....YIKES!....that ain't good Fuel economy in W-VA and Va thru with the steepest grades dropped even lower, one tank only netted about 4mpg's.

I spent the rest of the trip trying to use manual combined with and w/o "tow-haul" to keep the truck from downshifting so far and having to sit there and squirm in the seat while the engine sat at 5000rpm's on every grade. NOT happening. When we got out of NC on 77 things return pretty much to "normal" and the engine pretty much stayed in high gear for the rest of the trip on flat ground. Even so it BARELY managed 11mpg's pulling that little trailer.

Loaded up the bike in Orlando and decided to come back I-75 as it avoids the big pulls for the most part. Didn't help one bit. With the additional 900 pounds in the trailer the truck kept seeking lower gears on nearly every uphill grade and the engine was SCREAMING it's ars off the entire time till you topped the hill.

It nearly cost me more for fuel than what I paid for the bike! Not really but fuel economy was HORRIBLE and I wasn't the least bit impressed with the 6.0 HD set-up anyplace. Unlike the Duramax I owned using the "manual" mode would not allow the operator to prevent downshifts and let the engine "lug" a bit. What a HORRIBLE set-up and I don't consider that particular combination worth two squirts of duck-poop as a "heavy duty" truck with decent towing capabilities. They may do OK for some, but sitting there in the seat with the engine about ready to explode and tach stuck at 5000rpms just isn't making it.......IMHO.......Cliff