I have a 97 LS400 with 190k I'm experiencing a loud intermittent vibration. It does not do it all the time but when it does it's quite violent sounding at around 2000 rpm. Sounds like an accessory pulley is going to come off or a rod come through the oil pan. I've had the mounts inspected and was told they where ok. But the sound couldn't be produced at the shop for the tech. He said mounts where good based on visual inspection. I thought to take off the serpentine to see if I was an accessory but with it not being a constant sound it might lead to false diagnosis. Any suggestions?

 

Still have my money on the mounts. Mine "looked" fine but were totally collapsed and throwing the whole driveline out of alignment. The transmission one is super easy to do and it relatively inexpensive

 

190k and they "look" fine?

Get a new mech, the mounts are likely toast.

 

yes the cracks are not apparent until removed. mine split into two! the cause for vibrations is usually the transmission mount, which isn't too expensive and is fairly easy to replace. the motor mounts are not as easy!

transmission mount at 150k! part number is as shown, as i have a 97 as well.

 

Thanks guys I'm going to change it if it's bad or not.