I seem to have a vibration when driving. It started immediately when I pushed the 4wd hi button this season. I used the 4wd for about 2 miles. Since then, it has vibrated at 50mph and above for about 3 weeks. Last week the vibration disappeared. It was nice to be vibration free for about 200 miles.
But today I used the 4wd for the second time this year, and the vibration is back.

Feels like a front vibration.
vibrates when in neutral. coasting above 50
Center console vibrates
Mechanic replaced both rear u-joints this spring 09
New tires summer 09

 

where are you feeling the vibration? in the steering wheel, your seat? what is it specifically?

 

I feel the vibration slightly in the steering wheel only above 50. Most of the vibration is in the floor/console, including a type of thumping/sound vibration which resonates through the passenger compartment. I may feel a metal knocking at slow speeds (less than 40)

 

It could be your CV shaft going out, check to see if there are any cracks in the boots. You could also had a wheel not balanced, check to see if there are missing wheel weights, or if there is any mud/snow/ice build up on the inside of your wheel. Those both happened to me and those were the problems. I hope this helps, weather those are the problems or not, at least you'll be one step closer.

 

Ok, I will look at the CV joints.
Thanks

 

What ya driving?

This only seems to occur after you engage the 4X4? Hi or Lo doesn't matter?
I would suggest that one or both of the hubs are not unlocking completely. My '05 Silverado has this issue at times and I resort to the old school reversing 10 feet to unlock everything method...sometimes it works others it don't.

 

Thats what I was thinking. (Not disengaging)
I read about a 4x4 engaging' cable under the battery box.

Any way to test that idea.
Jacking up front end, spin one or both tires and see what moves in the front drive train?

 

I finally got a chance to looking under the battery tray. The cable moves freely, but the is always vacuum on the actuator. If it is 2hi, the cable is pulled and there is vacuum to the actuator. If it is in 4hi, the cable is still pulled and there is vacuum to the actuator.

Is this correct? Seems to me in one or the other, there should be no vacuum, or vacuum depending 2wd/4wd setting.


Thanks in advance.
Bob

 

There should only be vacuum on the actuator when in 4HI or 4LO. No other time. Sounds like something is amiss with the vacuum control to the actuator.

But lets get back to basics here. What are you driving? What transfer case do you have (it can be identified by the tag on the transfer case as well as the transfer case switch configuration)?

 

Hello again, thanks for your help
1995 blazer s-10 lt
not sure of transfer case.
vibration at highway speeds
Checked all fuses (ok)
2hi indicator light doesn't light, but the 4hi and low do light.

I just did a test, unplugged the vacuum line from the actuator under the battery, and plugged the vac line. Reinstalled battery and went for a ride...smooth as glass! No vibration.

So you are correct, there should be no vacuum at the actuator.
Advance Auto has the vacuum switch for the transfer case for $28.00, but could it be the push button switch on the dash? (3 button electonic switch)