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Dan
Dan, Technician
Category: Chevy
Satisfied Customers: 24584
Experience:  Independent Shop Experience, 2 Year Automotive Diploma, & Access to Information Database
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2002 Chevy Trailblazer has vibrations even after changing motor mounts

Resolved Question:

With a 2002 Chevy trailblazer 4.2 I have a vibration that occurs at low idle, it goes away when the rpms go up. I have changed all 3 motor mounts and it still happens. Would the harmonic balancer be going bad or would it be on the flex plate of the transmission?

Submitted: 7 years ago.
Category: Chevy
Expert:  Dan replied 7 years ago.

I would replace the balancer after the transmission mount. But sometimes when you have misfires it’s not bad enough to throw a code so you might want to consider having vehicle monitored on scantool to show there is no misfires but if that has been done and it runs right then I would do that after transmission mount. Let me know if you have questions, thanks.

Customer: replied 7 years ago.

I have replaced all three mounts including the one that sits at the rear of the engine, do you mean the cross member supporting the transmission, otherwise it has already been done.

Expert:  Dan replied 7 years ago.

Correct, replace the one on the cross member to see if that takes care of it.The Fairly common problem if not you will need to have some more diagnosing done with a high-end scan tool. Let me know if you have questions, thanks.

Customer: replied 7 years ago.

it is not showing any misfires, I have wondered if there was something up with the harmonic balancer or the friction plate at the rear of the engine

Expert:  Dan replied 7 years ago.

Harmonic balancer is a possibility I highly doubt the flex plate would cause this. When its vibrating you should be able to use a pry bar to put pressure on the transmission mount to see if that stops the vibration or even use your hand to see if you feel a lot of vibration where that mount is if so replace. If not the next step would be to replace the harmonic balancer. You could also remove the drive belt and make sure it still vibrates to eliminate anything else as a possible cause. Let me know if you have questions, thanks.

Customer: replied 7 years ago.

During the investigation I have removed the belt during and it still does vibrate. At what point would you lean towards the balancer?

Expert:  Dan replied 7 years ago.
I would replace the balancer after the transmission mount. But sometimes when you have misfires its not bad enough to throw a code so you might want to consider having vehicle monitored on scantool to show there is no misfires but if that has been done and it runs right then I would do that after transmission mount. Let me know if you have questions, thanks.
Customer: replied 7 years ago.

Have you seen this in the trailblazer/envoy/bravada/rainier very often? The balancer appears intact and the rubber/plastic sleeve seems ok, is there anything I should be looking for on the balancer or the transmission cross mount?

Expert:  Dan replied 7 years ago.

I've seen it on the engine mounts and transmission mounts but not the balancer but know that could cause the problem. On the mounts, you would want to look for worn spots where it’s contacting metal, bent, out of place, cracks. You could also remove the balancer to see if the problem still happens if not that isn’t the problem. Let me know if you have questions, thanks.

Customer: replied 7 years ago.

One last question I promise. The vibration appears to only be noticeable at low idle. When it revs up it seems to go away, does this point towards the trans mount?

Expert:  Dan replied 7 years ago.

Yes, that would point more towards a transmission mount or misfire at the low idle problem because if it was something else such as a balancer it should vibrate at all engine rpm. Let me know if you have questions, thanks.

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