Guys, I am completely stumped.

It all started when I decided to do the D25/bilstein install. Since the install, I have had a mysterious part-time cab resonance that I CANNOT find the source of! I have established only that it is linked to engine rpm only, so it's not a driveline (speed-dependent) vibration.

The spring/shock install went as normal as i could hope for. I ended up loosening the bottom trailing arms at the frame to gain enough droop to install the springs.

When i put the truck back together, I noticed there was a cab resonance that seemed mostly when I turned left, and seemed to go away when i turned right, even a little. Since I ruined my track bar doing the install, I attributed this resonance to the 1/4" or so of play in the track bar.

So I ordered and installed the DT track bar. No play whatsoever, yet the resonance is still there. It practically disappears when i make a right turn. It's VEry noticeable when I make a left turn. Going straight, it's usually there, I suspect because of the crown in the road acting like a left turn somewhat.

Track bar eliminated, I suspected a loose shock. Nada-- i cannot physically tighten the shock bolts any more.

I have also tightened (w/ a 1/2" breaker bar) the engine mounts (barely moved), the trailing arms (couldn't budge them, since I used an impact on those), and almost every nut or bolt I can find in the front end- tie rods, drag links, pitman arm, idler arm, you name it.

Still I have this mysterious resonance that sounds a lot like the shutdown shudder, only the whole cab resonates. You can feel it in the wheel and the shifter too.

I have a driveway with a slight incline and a big curb. When I approach it, the resonance stops as I make a right turn towards it. Then, when the truck starts swaying back and forth a couple times (from taking the bump at our driveway entrance) , I can hear the resonance start and stop as it transfers weight from side to side!! When i finally park, the resonance is really bad as it just sits there and idles.

I kinda suspected it might be the rear shocks (since I haven't checked those) but I did the rears first, and there was no resonance aferward. Not until I tore apart the front end did I get this resonance.

The Bilsteins that I have are the longer fronts (for the D25s) and tightening the upper mounts means tightening a 3/4" nut while holding the stud still with a 6mm Allen wrench. I can't tighten them down any farther!

The spring isolators are there on both sides above each spring.

As much as I LOVE the ride and look of the finished product, I am at the point where I wish I never touched the front end. Will I EVER get my smooth front end back?

Please help-- I feel like I have tried everything and don't know what to try next.

Justin

 

This may be off in left field somewhere, but what about the cab mounts? Maybe one starting to go bad???


HTH

Jim

 

Gotta say it.

Try pulling your front driveshaft and see if it goes away.

Have heard of many who went with the D25's or higher that have the front driveshaft vibe.
99% of them have an automatic transimission as well.

Later 2002's don't have the axle disconnect, so the front driveshaft is turning all the time.

I didn't have a vibe with 2" spacers, but with the 4.5" skyjacker I have a vibe.
Pulled the DS for a week and it went away.

I know you said it isn't speed related, but well worth a shot, since others have complained about it.

Since it only happens during left turns (more weight being on the left side, driver, fuel, etc) the angles would change more prominently with the vehicle weight being shifted to that side.
Especially since the OEM springs were heavier on the left to compensate, and the D25's most likely aren't (or they'd be different part numbers).


phox

 

It's not the driveshaft. It will resonate even when it is idling in neutral and the driveshaft isn't spinning.

I suppose I could check the cab mounts, but why would it only be after the D25 install that the resonance started?

Justin

Edit: note from my sig that I have the 6-speed.

 

That question is why I hesitated to suggest the cab mounts, but when you talked of the noise showing up during left turns only, the cab mounts came to mind. It is probably not the cab mounts, but that is all I could come up with ???.

Jim

 

[quote author=HOHN link=board=5;threadid=22355;start=0#msg209272 date=1068742607]
Edit: note from my sig that I have the 6-speed.
[/quote]

I always get confused which is which, ETC and ETH.


phox

 

Justin have you checked to make sure that one of the shock bolts is not bottoming out before getting the shock all the way tight. sounds like maybe the harmonics at some rpms are causing a shock to resonate you say you can not tighten the shock anymore but if the bolt bottoms out it would feel this way also as you turn it would cause a llose shock to unload. You proly thought of this one already but sometimes the simple stuff is hardest to figure Hope you find the problem soon

 

Well, I also have a noise that is driving me crazy that I would describe as a resonance of some sort. I have an '01 2500, Club Cab, auto....bone stock. Sounds like someone struck a tuning fork & mine also gets louder when I turn to the left. Been to three mechanics. One says brakes, one says power steering pump & the third is clueless. Brakes have been checked (twice) and are fine. I don't think it is the power steering pump because turning the wheel has no effect on the noise. I believe it is louder when you turn to the left because the wheel well is opening up and you can hear it better from the drivers seat.

My thinking is that it is related to the exhaust system...maybe something loose internally...debris...whatever...a loose mount or hanger. If I find the cause of mine I'll post it here...you do the same :-)

 

Suggestion: Because this only happened AFTER you installed the shocks it probably is somehow connected. So how about removing one shock at a time and see if it goes away.

 

??? Did you put the rubber pad back on the top of the spring ??.....Pete

 

I have seen the front suspension telegraph noise into the cab when a wrench slips down between the front frame rail and the cab, and gets stuck there.

The other thing to check is to be sure that the shocks are not so tight as to create a metal to metal contact somewhere. You want the rubber compressed only slightly.

Lastly, the best cure for strange cab noises is a couple of cans of the aerosol bed liner. It is a thick plastic stuff that squirts out and can be applied to various bare metal panels under the cab and in the front plenum, and dampens vibration. The down side it that it has to be 70 degrees for 24 hours to cure. I suppose undercoating would also work, but I dislike the sticky tar that is there forever after I use that stuff.