Any ideas about this weird shudder vibration.....

2008 Tahoe LT 4x4 90k miles. New brakes/rotors fr & rr. When slowing down from about 30 mph I hear and feel a subtle shudder or vibration, not strong, most passengers can't feel it. Interestingly when I put it in neutral the "sensation" goes away......something in the drivetrain?? While trying to figure out what's causing this I discovered the drivers side engine mount was busted in half so I replaced it and figured I'd found/fixed the problem. Well it is definitely better but the shudder is still there. Got under the car this morning with a pry bar to "test" the tranny mount but couldn't get enough leverage even after jacking up the front end but it feels solid. A close inspection with lights and mirrors shows the mount to be clean with no cracks. Anyone have any ideas?? thanks

What about the passenger side engine mount? Any signs of driveline u-joint problems? May need to remove them and check the u-joints with your hands to see if any binding. Any other recent work done? Tire conditions and tread wear conditions?

When you do feel the shudder/vibes, is it in the seat of your pants or in the floor thru your feet?

PNW VietVet said:

What about the passenger side engine mount? Any signs of driveline u-joint problems? May need to remove them and check the u-joints with your hands to see if any binding. Any other recent work done? Tire conditions and tread wear conditions?

When you do feel the shudder/vibes, is it in the seat of your pants or in the floor thru your feet?

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Thanks for the reply Ron.
I tried as best I could to inspect the pass side engine mount. Didn't see any fluid but it's hard to see anything on that side. If you know of a way to test it I'd love to hear.
U-joints look good from front to back but I have not removed them. This Tahoe has a really clean undercarriage. No other work done and tires are only a year old.

It's hard to describe but I'd have to say I feel it in the seat of my pants. It's definitely a new sensation and I'm afraid it's a symptom of something that's going to damage something more expensive than an engine mount.

Sorry for the delay, wife decided she wanted to see an early movie and dinner for V-Day!

Typically a seat of the pants vibe is from the drive line or something underneath. The floorboard typically is up front of you, like in the engine compartment. You can test engine mounts by a quick throttle snap in reverse and drive to get the engine to torque left and right or side to side. The new mount should hold nice and tight with a little bit of a rise or flex when the engine tries to pull up and away from it. If the other mount is going bad or is bad it will move way more and even jump up as it separates. You will need someone in the cab that you trust to do the snap throttle and hold the brakes nice and tight and set the park brake.

pop the hood, put your foot on the brake, put in it gear and give it gas, then put it in reverse and give it gas, observe the engine thru the hood gap while doing this.

Our last tahoe had a slight shudder on deceleration, going down a long grade off throttle and than lightly applying the brakes would really pronounce it. turned out to be rear diff carrier bearing, swapped out the entire diff 342 for 373 and it was gone. salvage yard, $350 inc labor. just my story, yours could be somthing as simple as a u joint?

Doubeleive said:

pop the hood, put your foot on the brake, put in it gear and give it gas, then put it in reverse and give it gas, observe the engine thru the hood gap while doing this.

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Thanks Ron/Wes, I did the "drive snap test" and found the bad LF mount but never dawned on me to do the same in reverse, doh. I'll chk it out.

thompsoj22 said:

Our last tahoe had a slight shudder on deceleration, going down a long grade off throttle and than lightly applying the brakes would really pronounce it. turned out to be rear diff carrier bearing, swapped out the entire diff 342 for 373 and it was gone. salvage yard, $350 inc labor. just my story, yours could be somthing as simple as a u joint?

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Thanks for the info John, much appreciated. Tahoe is going to be in the body shop for a few weeks starting tomorrow so I'll look into this the I get her back.