Lack of Towing Power

Just purchased a 1999 K2500 Suburban with 7.4, 4:11 gears, 57K. I bought this vehicle to tow my 20 ft boat and gear for regular camping trips up in the Sierra's of Northern california. My boat and gear weigh in at around 5500-6000 (Trailer, gear, boat and gas) so from all that I read and researched I figured the sub with a 10K towing capacity should have no problems handling it. Long and short of this post is this, my Suburban towing performance is worse then my previous truck (C2500, 3:41, 350 TBI) and I'm looking for any info that may explain why this is so. On top of that this truck eats fuel at an alarming rate and the end result is I'm one unhappy camper, no pun intended. I have not started throwing parts at it, it's all stock. Any help is appreciated.

Have you checked the obvious like Tune-up, Filters, Plugs, etc?

Is the SES light on? Are they oversized tires? Has fuel pressure been checked? Is the trans working properly(even when unloaded)?

Towing 5500-6000 lbs. shouldn't be too difficult.

Don't expect 20mpg though...

Thanks for the reply, the tires that came with the vehicle when I purchased it are 265/75/16, the stock tire size is 245/75/16 so the current tires are slightly oversized. The vehicle runs perfectly, no SES light and I did have it back at the dealer prior to my last trip and was informed there were no codes stored. As to the status of the filters, plugs , wires and other tune up parts I have to assume they are in good condition since I have not changed them and visually they look to be in excellent shape. Fuel pressure has not been checked and the transmission seems to be working properly. I did not suspect any of these issues because as I stated, the truck runs like new. As far as gas milage, I would be happy with ten miles to the gallon if I had the towing power I need.

Changing from 245 to 265 tires is about 1 inch difference - No big deal.

Saying that you think the Tune-up is fine without looking at your plugs doesn't mean anything. They all look good from the outside. You have to pull them out and read them. Also, looking at your fuel filter won't tell you much. If you don't know the last time it was changed - Change it - Cheap Insurance. Cut it open if you want to really find out if that was your problem.

A lot of times a vehicle will run fine until you load it up.

A simple Tune-up could fix your problem.

Your Suburban shouldn't even FEEL this trailer behind it...

Not sure how to react to the tune up remark but thanks for the verification on how the truck should pull the trailer with no problems. Going to take the truck in for or accomplish the 60K tune-up myself in not to distant future. The only problem is I really wont know how it affects the truck until I take the trip again.

If it sounded malicious... Sorry, it wasn't meant to.

Start simple. A Tune up is good. It has to be something obvious to affect towing power like you describe.