Last week's escalation to the service manager got additional attention on the buzzing noise, getting the shop foreman involved. They did contact Gaudin Jaguar in Las Vegas but were still unsuccessful in reproducing the noise on the lift, although it could still be heard on a test drive.

A very thorough inspection of the underside revealed there was a heat shield rubbing on the left side exhaust, the right side exhaust was loose at the coupler in front of the differential and finally the fuel filter bracket was not bolted in place.

BTW, for that last one, I'm now fully convinced the XK8 will NEVER again go to our "family" mechanic who has taken care of our less exotic vehicles for many years.

Anyway, all the above mentioned problems were corrected and the noise still persists, under light load at 45 to 50 MPH with the transmission in "Granny" mode.

There are some additional constraints I need to let y'all know here. I purchased an extended vehicle warranty in October of 2010 with the purchase of the vehicle. It is for 24,000 miles or 24 months whichever comes first. I've got 10,000 miles and nine months to go on it. Got most of my money back from the warranty but this buzzing problem might be very expensive.

The shop foreman's judgment is that the problem is not in the transmission, torque converter or the propeller shaft. To do further troubleshooting with an intermittent problem like this would get very costly and not be covered by the warranty. We have decided at this time to try the wait and see method and hopefully it will be more diagnosable (is that a word?) before the end of the warranty period.

 

I'm putting mine in the tranny shop Monday. The focus after their initial evaluation on the lift and the road test is on the differential, especially after I told them most of the buzzing occurs with slight throttle reductions. That got them thinking of the sun gear/planetary gear relationship in the diff, and how the diff moves up and down with acceleration/decelleration.

The boss wasn't in yesterday when the initial eval was done, and he wants to hear the buzz Mon, then decide if it's likely that they'll find anything on a teardown. If it's not loud or distressed sounding enough, like your shop manager, he may advise to wait a while before looking inside. I've got another two years on my warranty, and it's all covered in case she blows lol.