Strange vibration at speed

[83rampage]

I know this isn't the best forum for this, but there is lots of thinking outside the box on this board, so here goes.

My 2006 mega cab (http://www.amazon.com/gp/search?ie=UTF8&camp=1789&creative=9325&index=automotive&keywords=mega%2Bcab&linkCode=ur2) 4x4 auto (3500 SRW) has developed a strange vibration over the last year or so.

Basically it is a vibration that starts around 65 MPH and gets progressively worse as speed increases. Around 70 MPH it becomes a vibration the comes in 1 second "waves". It vibrates-stops-vibrates-stops at about 1 second intervals.

Truck is very low miles at 50,000 original miles. I am the original owner and this truck is almost 100% stock with 2 exceptions: 1 piece aluminum driveshaft and 285/70/17 Bridgestone tires. Never had a tuner on it at all and has never been off-road or abused in any way.

Vibration is speed related but it is worse if under power, as opposed to when coasting.

Things done to troubleshoot:

1. Changed tires. The originals were dry rotting so put on new Bridgestone Revo tires 1 size bigger than stock.
2. Changed out 2 piece rear driveshaft. When this vibration first started my first thought was u joints or center bearing-Great excuse to upgrade to a 1 piece aluminum driveshaft. Had one built by a local shop with new u joints.
3. Removed front driveshaft.
4. Rebuilt transfer case with a bearing and seal kit. Never replaced the chain because it was still in good shape. All internals looked in fine.

My next thought was maybe the engine/transfercase mounts are getting weak, but I don't want to just throw any more parts at it.

Any help here would be great.:eyebrows:

[black86glhs]

I have seen worn front track bars cause this. Might as well check all the steering components while in there. Check the outer front u-joints and the front hubs(bearings). Don't think because it is lower miles all is good.

[Vigo]

So it changes under power, that's good. Drop a gear and see if it changes based on rpm. If it does it's most likely coming off the engine/trans/t-case. If it doesn't it probably has something to do with the things that DIDNT change speed when you shifted, from the driveshafts all the way out to the tires.

[83rampage]

So it changes under power, that's good. Drop a gear and see if it changes based on rpm. If it does it's most likely coming off the engine/trans/t-case. If it doesn't it probably has something to do with the things that DIDNT change speed when you shifted, from the driveshafts all the way out to the tires.

I should have explained that more fully. If you kick it in neutral going down hill it is still there, just not as noticeable, so it is speed related, not engine RPM.

I think I can safely rule out tires, driveshaft and Tcase. Not much left that is speed related. I should also mention I checked the magnetic fill plugs on the diffs and they look "normal.

[83rampage]

I have seen worn front track bars cause this. Might as well check all the steering components while in there. Check the outer front u-joints and the front hubs(bearings). Don't think because it is lower miles all is good.

Those are some good points. I actually did also replace the the RH front wheel bearing and that u joint was fine, but Ill check the left.

Never thought to check the track bar...

[ajakeski]

Dodge redesigned the 4WD steering linkage due to instability. I don't remember the exact years affected but it was in the early 2000's.

Search "Deathwobble" on Google. There is a lot of info out there.

http://www.dodgeproblems.com/trends/death-wobble/

[black86glhs]

Those are some good points. I actually did also replace the the RH front wheel bearing and that u joint was fine, but Ill check the left.

Never thought to check the track bar...I had a 97 come into my shop that had a nasty shake above 45 mph. The kind that made your teeth hurt. We tracked it down to the track bar on that one. It was completely wiped and not sure how it didn't pop off. Yours, if it is, obviously isn't going to be as bad. Also check the steering stabilizer.
this truck is the only reason I know about the track bar. Otherwise, I wouldn't have guessed it.

[DaveSkrab]

I am not overly familiar with the setup on that vehicle, but what you describe sounds like a rear driveshaft u joint. So that got me thinking, does the tcase rear output use a bushing? Was it replaced during the overhaul? Maybe it's worn enough for the driveshaft to wobble at the slip yoke. Hope this helps.

[83rampage]

Thanks a lot. I really appreciate the input.

Although I wouldn't call what is going on death wobble, I got to thinking it may be that in its infancy before it gets into full blown wobble (from worn parts later on in time), so along with the track bar I'm going to give the front end a good going over. Ive driven vehicles with death wobble and this isn't anything like that. You really cant even feel the vibration in the steering at all on my truck and it is vibrating consistently all the time, not just initiated by hitting a bump, but at this point anything is possible.

The driveshaft bushing in the tcase was also changed when it was rebuilt so we can cross that off the list. When I started noticing this vibe I would have bet money that it was u joints so I was floored when I spent all that money getting rid of the crap 2 piece driveshaft to a shiny new aluminum 1 piece and it did squat. That is also why I took off the front driveshaft with the same result.

Ill do some checking next week and see what I find.:confused: