I've got a 2003 laramie, 4wd crewcab. I'm pulling a 21 ft. fifth wheel, dry weight under 5000#. The truck seems like it doesn't know when to downshift. In mountain passes, I drop down to 10-15 mph often. It will suddenly downshift, taking me up to 5500rpm. I've tried playing with the throttle as I'm driving, and sometimes I can avoid this.
I'm used to pulling construction trailers with work vehicles, so it's not like I'm out there winging it.
I used a superchips programmer with the tow setting last year. This year I ran the truck without it. I've got a k&n cold air intake, other than that the truck is stock.
The truck has 112,000 miles on it. Runs great the rest of the time. I changed the plugs at 96,000 and had the transmission serviced. Never had to do one bit of work to it other than that. I always turn the OD off when I'm towing.
I tried resetting the TPS last year, but that didn't change anything. I really like the truck, but I can't keep pulling through the Rockies at about the same speed I could walk. Anybody got any ideas?
Thanks everybody.

Try this to see if it doesn't help.

1) Update your tuner and re-tune your truck to Tow mode.

2) Reset your PCM, follow this link: http://hemitruckclub.infopop.c...860022075#3860022075

3) With that done, re-calibrate your throttle body (this should work even for trucks with the throttle wire): Turn key to ON (DO NOT START), mash the gas pedal to the floor and hold it for 5-10 seconds. With the throttle still floored, turn the key to OFF and wait another 5-10 seconds, slowly release the throttle.

4) Put the tranny in "Tow/Haul" and see if there is any difference towing your trailer.

Thanks for the advice- I'll give it a shot today.

Finally was able to get the trailer out on the road after I followed your suggestions. Seemed to be a huge improvement. Of course, the mountains here in Kansas aren't as tall as the ones I was pulling through in Colorado. But I appreciate the advice tremendously!
Thanks again