Why would you need a 4x4 truck to go over 90 MPH....?

Maybe to solve this problem you just shouldn't go over 90 MPH.....

 

I hate to say it, but, I have seen more than one time on the Chicago freeways were the NORMAL flow of traffic was doing 85-90 mph, that includes semi rigs too. There is --in my opinion-- no reason why these trucks shouldn't be able to run 90 all day long, whithout having the fear of something mechanical taking a dive in a properly maintained truck. I've been fighting a 60mph vibration on mine for quite q while now, and its a steel drive line (good u-joints). I thinking that its the rear cone on the transfer, because there is side to side wiggle on the yoke, which will amplify any minor imbalance on the drive line.

 

Vibrations are hard to diagnose over the internet, mainly b/c there are so many components that can cause that problem... But on most Mega Cab 1500's as well as 2500 and 3500's a lot of vibrations can be attributed to "death wobble"....

Other common suspension problems can be caused by bad tie rod ends, bad shocks, and even something as easy as a weight overload or an improperly loaded toolbox. I remember a friend of mind nearly replaced everything suspension related on his F150 Stepside, and still had problems with tracking to the left and vibrations at higher speeds, well I opened his bed tool box and saw that every single one of his tools was loaded on the driver's side... well I moved half of them over to the passenger side of the box and all his problems went away... it was like magic... lol

If it is indeed driveline vibration then my next area to inspect would be the yoke and bearings....

If the truck is lifted I'd check the driveline angles and see if they are too steep causing binding and/or other related issues.

Then I'd start to look at the transfercase, input/output shafts, transmission internals, and driveshaft balance, which is right where it starts getting expensive.

 

*Warning* Before going 90 plus in a LIFTED TRUCK, one should consult with the local cemetery.

 

Agreed.....

 

Also, if you are diagnosing a vibration, I wouldn't keep pushing it faster and faster, you are just asking for trouble. Once you get a sense for where the vibration is coming from, it is time to get under the truck and check for issues, not drive it faster.