Bad vibration under load

[Tulip]

Hey guys, I haven't posted on here in quite a while but I am needing your knowledge base in the worst way. I have an 04. 5 3500 6spd with 101K miles and I am running 35" Procomp X-Terrains on KMC XD Rockstar rims. I am experiencing really bad vibrations while towing with a 34ft gooseneck trailer, however, I don't experience the vibrations without the trailer when I am driving down the road. I replaced the carrier bearing less than 10k miles ago due to it being completely worn out, and I have checked it, it is fine. I checked the transmission mount by pushing up on the transmission to see if the rubber mounts had any flex and it seems to have a little movement in it. I had the rear ujoints replaced under warranty at 32K miles, so it might be time to replace them again. I am also running air bags at 70lbs when loaded with the gooseneck. When driving down the road you can physically see the transfer case shifter vibrate in a cyclical fashion, meaning, you can feel the vibration for about 5 seconds, then it stops for 2 seconds, then the same pattern happens again. To me, there are only a few things that it could be and should be done in the following order:



1. Balance tires

2. Replace rear ujoints

3. Replace transmission mount



What are your thoughts? Am I missing anything in my thought process or am I going down the right path. My concern is that I can throw a lot of money at this and still no resolve the issue. Sorry about the long post, but I wanted to give you as much detail as I could. Thanks in advance.

 

[cerberusiam]

What air pressure are you running your tires at?



Loaded does the stance change or do the air bags keep it where it is unloaded?



Sounds like u-joints, but, tires and changing drive line angle will sometimes cause a rythmic vibration.

 

[Tulip]

When loaded with the gooseneck I run the tires at 50, without the gooseneck I run the tires at 45. The air bags keep it really close to where it is when unloaded. Didn't have this vibration with the same setup 5 months ago.

 

[cerberusiam]

How can you run that tire at 50 psi with that much weight on it and NOT have problems?



A tire rated at the load that trailer is capable of putting on it runs 80 psi to handle it. Have you tried airing the tires up so see if that changes anything?

 

[Tulip]

Not had issues in the past with 50 but can definitely try it.

 

[Wingate]

If air pressure doesn't help it, you might go back and re-check all the u-joints ( front drive shaft included) to make sure you don't have a seized u-joint.

 

[Tulip]

Forgot to add in the orginal post, the front driveshaft ujoints look good and move freely.

 

[Chief USA]

Just a long shot. Have you checked for codes? Could this be a weak cylinder that may be intermittently missing under load?

 

[p-Bar]

A lot of these early AAM ujoints didn't get enough lubrication from the factory , did you check these when the carrier bearing was replaced?

 

[Tulip]

Engine is fine, no missing or anything

 

[Tulip]

Yeah the dealer replaced them with factory AAM joints at 32K and that was 70K ago, so I suspect that is the issue. No I didn't check them then, because the I attributed the small vibration then to the carrier bearing.

 

[p-Bar]

I was at the SEMA show a few years ago and spoke with the rep from AAM and said they had some "manufacturing issues" with u joints and drivelines. Try a different vendor and maybe something with grease nipples

 

[sag2]

Install one of the shorter center support brackets. There is an older TSB that gives the part numbers and I have also posted several times with the repair procedure.

 

[BDaugherty]

Did it start after having rear end work done? Did they have the rear shaft out?

Move your air bags up and down and inch or two and see if that changes anything. Next check your rear Ujoints. You will have to remove the driveshaft to check them. Did it start after your carrier bearings were replaced? How much backlash is in your differential? While you have the shaft loose, check the pinion bearings. If all this checks out, rotate the tires. Remove the front driveshaft and tow without it. If the vibes are gone, it's in the shaft. Also, the TSB mentioned above sounds like something to look into. Does your truck have a midshaft bearing? If so, look at it closely. Trans mounts would be toward the end of my list. I would do all the legwork first without spending any coin. Also, check your trailer for any vibe problems that could be transmitted.

 

[JWadford]

please dont air your tires up over the max inflation pressure on the sidewall, and you are most likely right about the u-joints, if you are running a stock engine, greasable u-joints from checker will work, but if you are pulling with over 350 rwhp or 650 rwtq you will want a good non greasable joint, the greasable joints will last longer if serviced correctly but are weaker due to hollow internal passages for the grease flow, a solid non greasable is stronger but usually wont last as long, also sometimes while you are checking the driveline u-joints, just prying up and down wont find the problem, a bad vibration could be caused by a tight spot that hasnt beacame loose and the only way to find it is to remove the driveshaft and physically move the u-joints to make sure they dont have a tight spot, hope this helps.

 

[Jack in Alaska]

vibration

It is u-joints. My truck had the same thing. Ok w/o towing, vibrates when starting out with a big towed load.

 

[Tulip]

sag I have tried to do a search on the TSB and the posts you are talking about but I did not find anything. You have a link?

 

[JohnBoy5]

I have a similar problem in my 2001 2wd. been trying to figure it out as well. Just had the entire drive line reworked and balanced. Still have it. all tires (truck and trailer) have been balanced i even replaced the tires on the truck. My vibration is only at 72 to 75 mph. Its violent also. Could a bent wheel on the truck cause this, not sure if i have a bent one but will be trying to look in to that Wednesday. I also have been letting the same people balance my tires but i will be doing it my self this week. Maybe their machine is not working right???

 

[Tulip]

I changed the ujoints in the rear driveshaft with the greasable ones from Napa.



I started thinking that it could be driveline angles especially since I have airbags. I noticed that it would vibrate bad when I had a trailer on it and airbags aired up to 70 psi, but wouldn't vibrate when I was not pulling a trailer and the air bags were empty. I loaded up the trailer and didn't air up the bags and noticed the vibration was hardly noticeable.



I have also started noticing that it is vibrating when I first start out (like the launch shudder on steroids). I am going to have the driveshafts balanced and see if that helps.

 

[JohnBoy5]

I had the drive shaft balanced and all the u joints replaced with greasable ones new tires on the truck and even balanced the trailer tires. I really think it could be in the trailer BUT the only thing that makes me think its not is the fact that its just so bad. I bought a camera today to hook up to my in-dash DVD player. I connected magnets to the base of the camera and plan to move it around on the truck and the trailer to see if i can see anything while i am driving. I will be driving 430 miles tomorrow with the trailer so i hope to figure something out. But who knows this could be a waist of money and i wont see anything but i think its still a pretty cool idea either way. Haven't you ever wanted to see the underside of the truck going down the road or see the turbo start to get a little red glow to it after pulling a big hill? I plan to look at all of that. Should be fun. If i see anything i will let you know, any chance you think it could be the locker in my rear end or the lash between the gears? I have got to figure this out thats all i know even if it wont hurt anything its driving me nuts... .

Hope i dont hit any road kill and get it on the camera tomorrow. lol