It seems to come from the rear suspension area, and it responds to throttle changes, buzzing when I either add or reduce throttle. It's a deep, harmonic hummimg/buzzing sound. Can the rear differential make such a sound? I think it's becoming more frequent, buzzing w/every change, but a few weeks ago it was more sporadic.

 

Does this happen while driving only or will you hear the buzzing with the car in neutral? Fuel pump going bad??

 

I just took it back out for a test drive/errand and it's only while driving. I also noticed that while at speed, when I placed it in neutral for a few seconds, it buzzed constantly and a bit louder, then would stop as soon as I placed it back in gear. Then if I made the throttle changes, it would buzz again though not as loud. Something to do with the drive shaft or U-joint?

 

You're hearing a LOW frequency buzz, is that right, Skid?

Not something higher frequency? Sounds mechanical and not electronic?

 

Yes, it's a low freq buzz. But this afternoon I took it on a 45 min road trip at 60-70 mph, and the buzz went away. After I got back into town I couldn't hear it unless I coasted in neutral, and even then it was much quieter. In fact I wouldn't have noticed it at all if I hadn't been listening for it. Maybe it will come back after driving around town for a few days, but whatever it was it was greatly diminished by driving some highway miles.

 

The sound has come back, and gotten worse, so I took the car into the local Jag dealer this morning. According to the service tech that rode with me the buzzing sound is coming from the transmission. He says it's probably either a cracked A or B drum, or a bad bearing.
They have it scheduled into the shop next Monday, at which time they will put it on the rack and isolate the sound's location in the transmission. They will then notify the claims adjuster from my warranty company to stop by and listen to the noise.
The tech said the remedy will be to replace the transmission with either a new or rebuilt unit, although the warranty company may prefer to use a used one. Anyone have experience with replacing an existing transmission with a used one? Should I insist, or even offer to pay the difference, for a new or rebuilt one?

 

My thoughts are used is used. Your transmission is used. Why replace it with a used one. I would opt to pay the difference for a rebuilt if all the co would ante up for is used,

 

offer to your warranty company for a rebuild with an upgraded A-drum, surely cheaper than an entire used or rebuilt transmission.

 

I'll mention the updated A drum, that's a good idea. Maybe find an already rebuilt one with the new drum since they probably want to just do a swap out.

 

The Jag service dept has had the car since Monday, and the tech is saying possibly it's a front or rear tranny shaft bearing. He says the noise is not loud enough or consistent enough yet to call the warranty adjuster. The tech wants it one more day to drive/trouble shoot.

I did some research and the Idle Control Valve sounds like a possible cause. Anyone have any experience with this? Would something like this come up in a computer diagnostic?

 

hmmm, not here, and I doubt it on the computer catching it. I've never heard of it actually.