DennisB

We just returned from a 1500 mile trip towing a 28 ft 5th wheel.
During the drive home we traveled a highway with several significant up hill hauls. I used tow haul whenever necessary. However, on one of the hills when I engaged tow haul, the rpm went up to 2800 and I felt three sort of engine misses. The truck did what I call bucked, then smoothed out. From then on, every time tow haul was used there was a "buck" but not like the first three.
This all happened at about 50 - 60 mph.
I wondered if anyone else has experienced this? My truck is a 3500 ctd automatic.
Thanks for your help.

Kampnnut

I recommend putting it in tow/haul before you pull out of your driveway and leave it there until you unhook. Putting it in tow/haul changes the shift points and when the torque converter locks up. If you put it in tow/haul while driving the transmission is adjusting to the speed and gear you are in and the higher rpms can happen while it is adjusting.

When I tow, I just put it in tow/haul before i pull out and leave it there. I even use it at times when i'm not towing. The torque conveter will lock up in 2nd, 3rd, and 4th then and you will feel a more solid shift. It will shift into 4th at about 45 mph providing you don't have your foot into it. When I get to 45, I usually let off the accelerator and let it shift into 4th then ease back on pedel. I do this if I don't need to get into to traffic in a hurry.

JuzPlaneKrazy

Dennis, I have had my truck do the same "Bucking" as you call it, a sort of a miss, while climbing hills around 7%-8%. I was told it was more than likely defueling itself because of high temps, high EGT's etc. I've never worryed about it after hereing that. And the truck runs fine after it levels out and EGT's and temps drop. with the Quadzilla Commander you can set alarm points and adjust defueling as you want it,nice feature of the Commander.

DennisB

Thanks to you both. I was pretty anxious after this happened. But these responses make me feel a heck of a lot better.