TOWING PROBLEM

robert1972

Hi all,
I have a 97 Dodge 3500 diesel with a 5sp trans. when I hook up my car transport the truck sometimes starts to bounce, it feels like if you step on and take your foot off the gas real quick and keep doing it over and over while driving down the road. I have noticed that a small bump in the road will set it off. The trailer is a 5th wheel/goose neck, it weighs 7000ibs but it doesn't matter if it is loaded with 16,000ibs or empty. I have added 2 springs and a new set of shocks and checked every nut and bolt while it was on the lift. I also hooked up another trailer and it still does the same thing. It won't do it empty though. I have been using this truck for about 2 years and the problem just started and seems to be getting worse.
thanks for your input.
R......

lariat1

Sounds like shocks to me. There are only 2 things that I can think of that cause the problem you have one is too much weight on the truck and the other is shocks. Being a 97 I would suspect the shocks. Monroe makes good heavy duty shocks that should work for many years and they are relatively inexpensive. Ranchos will also work but they cost more and are tuned more for off road use.

robert1972

I did replace the shocks, and I also thought about the weight, but empty it weighs 7000ibs, which that truck should handle with no problem. The other thing is, it makes no diff. if it is loaded or empty (7000ibs to 16000ibs) it does the same thing. Like I said, it doesn't bounce up and down, it feels more like flooring it and letting off, doing it quickly (example 7-8 times in a 5 second period).

Thanks for your input though
R.....

lariat1

Is the trailer tongue parrallel to the ground at all times? A friend had a 3/4 ton GMC that did the same thing. It took me a while to remember about it but it had something to do with a lot of tongue weight and the trailer tongue was slightly pointed down, it would cause the weight to shift on to the truck and compress the suspension.
Just another thought anyway.

robert1972

actually it's a goose neck not a tag along. And also I have been using it for about 2 years now and the problem just started about 2 months ago.
R.......

richcolo

What happens if you let off the accelerator and push in the clutch? I have driven one early (1990?)Dodge/Cummins where the combination of driveline slack and the governor combined to produce a very pronounced repeating front and back jerk. Only pushing in the clutch or flooring the accelerator would smooth it out, and flooring it only worked if you weren't already near max RPM, which you often were because of the 4.10 rear and low RPM capability of the 12 valve Cummins. It also tended to start when you hit a bump, possible due to unintentional accelerator position changes, or maybe motor mounts. I never pulled a load with that truck (wasn't mine), but I would think it would have been pretty nasty if it started jerking with a load behind it.

robert1972

Yes if I let off the accelerator it does go away, I don't have to push in on the clutch. Also if I floor it, it will go away. Do you think that there is that much play in the drive train with only 80K on it?
It sounds like the one you drove had the same problem, but mine will not act up running empty.?
thanks
Robert

richcolo

As I recall, the truck I described had right about 100,000 miles at the time. Unfortunately I don't know what the fix was (or even if it was fixed.) I would take a real close look at the motor mounts. If that isn't it, I'd look for a mechanic with some Dodge/Cummins experience. The Turbo-Diesel Register on-line community might have some good information for you as well.

Good Luck