Motor mount vibration and 4WD

[Ohiogators]

Purchased my 2005 Envoy XL SLT I6 2 weeks ago (108K miles). I have a vibration that I thought was coming from worn motor mounts and had plans to replace them when some warm weather shows up here in Ohio. The vibration comes through the accelerator and I can feel it through my foot. As the car moves up and down while driving I can feel the vibration stop and start as the car bounces. It seems very slight when barely accelerating and goes away completely when in park.

After getting a little snow last night, I switched over to 4WD and the vibration went away completely at any RPM. Now this has me thinking I may have misdiagnosed this as motor mounts.

I do have a noisy rear end, and I'm pretty sure it's just shocks and sway bar links out back. I've already purchased all 4 links and a pair of bilstein HDs for the rear.

Have I misdiagnosed the motor mounts?

 

[CaptainXL]

This is a bad motor mount where its obviously separated. But in our case with the fluid filled mounts they can become deflated. Check for fluid leakage.

[video=youtube;RVwZHn6ISr4]http://www.youtube.com/watch?v=RVwZHn6ISr4[/video]

 

[The_Roadie]

Could be CV joints, but the test is if the vibration is proportional to engine RPM or road speed.

Bad motor mounts usually show up as a precise 10 Hz (same as our 600 RPM idle speed) rotational vibration that's worse in DRIVE than in PARK. Can't be seen as a moving needle on the tach because 10 Hz is too fast for that.

 

[Ohiogators]

So CV vibration tends to go away with 4WD engaged?

 

[floridafitz]

My experience with bad motor mounts...one had deflated / leaked...was vibration was most noticeable with engine running, in drive with foot on the brake. Classic situation at a red light. When I would shift to neutral, keeping foot on brake, the vibration diminished. Not really evident while underway.

 

[BillyBoy]

Very old thread, I know, but I will take a chance. When changing motor mounts on an 03 TB 4.2L 4x4, which direction do you reach in to remove the drivers side mount? I have looked from above, from below, front, back, etc... I just don't see where to reach in there to remove the mount and put the new one back in. It looks like removing the alternator could give access but in all of the threads I have read, no one mentions having to do that.
Any ideas?

 

[kkeo211]

Very old thread, I know, but I will take a chance. When changing motor mounts on an 03 TB 4.2L 4x4, which direction do you reach in to remove the drivers side mount? I have looked from above, from below, front, back, etc... I just don't see where to reach in there to remove the mount and put the new one back in. It looks like removing the alternator could give access but in all of the threads I have read, no one mentions having to do that.
Any ideas?

When I did my mounts I didn't have to remove the alternator to get to the driver side mount. What I did was remove the bracket that it mounted onto. I tried grinding the top of the new motor mount off a little bit but could never get enough clearance. I took about 4 to 5 hours to get both mounts in, but well worth it knowing the cost at a shop.

 

[BillyBoy]

Where exactly did you reach in to get to that driver side mount?