98 2500 4x4 68K original Automatic. Going up the mountains pulling my trailer, as soon as it shifts to 4th gear at 45 mph, the truck will make a popping sound and buck a few times. It will continue to do this until it gets to 50 mph and then nothing. I noticed a lot of black smoke coming out of the exhaust when it is doing this. If it were a gasser, I would think that it is misfiring. It really only does this when it is under a pretty heavy load. Any thoughts?

 

Is your truck fairly stock? or do you have a modified exhaust? Maybe egt's are soring high? and since your an auto. isn't 4th overdrive? or is 5th overdrive? I thought in 2nd gen dodges the auto had a 3 speed with over drive. Could be wrong as well. But i'm probably wrong. kicking in overdrive under load at 45. no way. never mind. But anyways Maybe your truck can't really breath? Unless it's fairly modified. what kind of mods do you have on it?

 

when was the last time you changed your fuel filter???

 

12 valve or 24 valve?

 

lack o fuel man!!!

change the :
air filter
fuel filter
check for fi pump leaks.

 

Thanks for all the tips. I have a 12 valve. The only mods that I know of is that a camplate was installed. Exhaust is stock and all filters were changed in the last 500 miles. My mileage sucks (11-13) so I was thinking it was more of to much fuel rather than not enough.

 

do you have an EGT gage??? if your EGT's are way high I would suggest cranking back your star wheel a few clicks.