I have just returned home after six months on the road as a snow bird pulling a 9. 000 # 5th wheel from Seattle to Florida and across USA to Arizona and then back to Seattle. my truck which is stock '97 2500 5. 9l with a 3. 54 rear end and a transmission cooler did great. However, I have some questions for the group. Why does locking the OD in the off position give me more pulling power even in the lower speeds and gears (way below the normal 40 mph kick-in speed)? Also, is it typical for a diesel truck (even without a load)to really feel sluggish from a dead stop up to about 35-40 mph? This is my first diesel and I didn't know what to expect when I first began driving it. Lastly, I am interested in pull a little more "umph" in my engine for pulling a load up hills, accelerating from 0, ect. but am not into racing, etc. What are the most cost effect modifications that have the least potential for damaging transmission, etc. I have installed a K & N air filter. What do you recommend next? Thanks Dan