Boondock

Sure someone will know what it is. I don't know and everything looks fine to me. Truck has 119K miles and I am buying new shocks for it this week although I don't think they are the problem.

The knock doesn't happen when empty unless I hit a really big bump or am going over 75 or 80.
Towing the boat it happens a lot of little and big bumps at speed above 50-55 or so.
The more weight and the faster I go the more it knocks.

Any idea what it is? About to take it to the dealership and let them look it over but thought I would check here first.
Thanks

Forgot to say the u joints have been replaced with bigger ones at around 105K miles.

Baja

Put on the shocks. Possible that the bushings are worn and the metal is hitting when you go over a bump.

Lurch

Tailgate still fit tight? My rubber stops have shrunk/worn down. Rattles like hell over bumps.

thumper549

Bolts holding pick up box to frame ?

RacerRon

I suspect you are hearing/feeling the overload springs bump the pads on the frame. Mine will do the same thing if there is not enough load in the bed to keep them in contact all the time. Look at the ends (top) of the overload spring, you can tell if they have made recent contact.

delliott

Do you have the camper package with the extra overload spring pack on top? If so, those will "knock" when they start to contact after about 2" of travel.

Empty, it takes a pretty good bump to hit them. Less of bump with more weight, which sounds like what you're describing.

There's also a rubber sleeve that goes around the arm that contacts them to help reduce noise/wear that may have fallen off. Or it could just be spring fatigue in the main spring pack causing them to contact more than before.

David

(On Edit: Looks like RacerRon beat me on the reply. That's what I get for taking too long to post. At least that's two votes for the same cause.)

Dinner

I would also check your Torsion Bar Bushings.

Boondock

Thanks guys!

Baja hope that is it.

Lurch interesting idea, I can shake it and it is quite lose but it knocks even over the little bumps with the boat behind. Without any load it takes a lot for it to make the noise.

549 Bolts look good to me

Ron, the heavier the load the more it happens. No load it really doesn't happen. Didn't see any contact...

David that makes more sense but wouldn't it show marks/wear? Have a pick of yours? I don't see any contact happening....

Dinner not a way to check them without taking them out? I looked at the bushing I could see and all had rubber around them.

Thanks again everyone

STate

Ive got the same exact issue w/ my 98 CC LB. Ive been telling myself to crawl under and have a look while someone is bouncing up and down on the bumper. I hope its either the shocks or maybe the overload springs (camper package w/ overload and rear anti sway). I just want to know what it is so I can either fix or ignore it.HAHA

Sidewinder

I had a similar noise on my truck. It was the crossmember at the back of the truck. The rivits holding the crossmember to the frame got loose. I drilled them out and replaced them with bolts. No more noise. You might want to check that.

Dinner

Boondock,

If you can grab the Torsion bar behind the axle and move it up and down within the rubber mounts, they are wore out.

The crossmember idea from Sidewinder is also a good thing to check!

thumper549

I think you would have to put a wrench to the bolts.....not just look (box)

Red3quarter

I had a knock in the rear of my truck when I would hit bumps. Turned out to be the endlinks and bushings in the rear sway bar were bad. Went to dodge and got the new parts to rebuild it and the knocking went away.

Dinner

My truck is the same, I can take my sway bar up and down and get it to click/knock inside the wore out bushings.

cheapskate

i had the same noise, and it was the rear sway bar end-links for me too. they are easy to replace.