I recently bought an 02 Dmax and separately an 02 Cougar 5th wheel. I took the 5th wheel for its first test last night and found that around 60-65 mph it has a surprising amount of front to rear bucking. You feel it, more than see it, but it does it roughly once a second or two. I had installed a slider hitch in my SB, made by Hidden Hitch (which is owned now by Draw Tite I think). It uses round rails with a standard double pivoting head and seems to be reasonably tight. The 5er is about 30', 7300# dry, and niether it nor the truck had cargo. I have new Bilsteins, but need to check all the tire pressures. The bucking is not rythmic, and seems to be less at 70mph plus. I was on new concrete, but it seemed fairly smooth. We went about 10 miles, maybe 1 of which was on blacktop, and the problem didn't go away on the blacktop.
Any suggestions? Is there a mod to my hitch that will stop this? Or did everything just add up wrong last night? Our first trip is May 28th, and I just hope it wont harm the truck if it does this the whole time.

Gary, Since I have your truck on the lift as we speak, I have looked at the bottom side and all looks well. I have to wonder about your problem being pavement related. I have noticed mine on certain stretches of load really gets moving... On other types of road, smooooooth

BLKMAX5,


Sounds like a condition called "freeway hop". If the Length of you 5er & pickup axel combination are just right, that is what happens. I have it occasionaly with my Ext cab & a 32" 5er. The only solution I have found is change my speed. It seems to happen more at 65 than any other speed.

Actually, since it happens both on blacktop and smooth concrete, "Freeway hop" or resonance doesn't sound as likely as porpoising due to low pin weight. You did say the 5'er was not loaded, right?


Easy to check out. Load the 5'er front storage area with several cases of water, make sure any water tanks (Gray, black, or fresh) located aft of the axles are empty and try it again.

I concurr with Sneaks. I've been following these sorts of posts for years now (rv.net) for one. Try filling one of your water tanks in front of the 5'er's axles with water. My fresh water tank (42 gallons) is slightly in front of the axles. Filling it full seems to make all the difference in the world. When I do this, I'm right at or a couple hundred pounds over the 9200 GVWR of the D/A. Seems to be the way it likes it.


Even with a perfect setup, if you've never towed before, you'll have to get used to the fact that whatever you are towing will remind you that it's back there...... every once in awhile.

I had the same problem. Added the rear Timben and Rancho RS9000. I have total control of the ridehttp://www.dieselplace.com/forum/smileys/Big Smile.gif. In April we went out west and put just under 6K in 3 weeks. 65 to 70 all the way, No Bucking!

Thanks guys for the input. I'll let you know how it turns out after the weekend trip when things are loaded up a bit more.

BLKMAX5, what kind of tires on the truck? (all terrains) Up here we have ruts in the pavement from tractor trailers. Occasionally you run into a section of road, where the ruts are so bad, truck and trailer start to move around.
As for the tires, I've heard that the all terrain tires have a alot of side wall flex. Causing the truck to squirm. And run your tires close to maximum psi.

My Wildcat did the same thing on our first run. Our fresh water tank is halfway between the axles and the hitch pin. I just make sure it is completely full and have not had any problems since.http://www.dieselplace.com/forum/smileys/Approve.gif