1st some short history - I got this car from my 86 y/o father, who bought it about 5 years ago. Shortly after he first bought it, I took it on a long mountain drive - nice twisties, and noticed a strange phenomenon: While taking a HARD, fast, sweeping right turn, beyond 90 degrees, a high pitched buzz or chirp sound (around 2-3 kHz at inception) would emanate from the area behind me and to my right, behind and to the left of my passenger... we finally decided it must be in the general area of the differential.

My first thought (from the mild... sort of screeching sound) was that perhaps a branch had been caught and was rubbing on the driveshaft or one of the halfshafts.. inspection showed that not to be the case.

The sound, once started by the high speed right sweeper, would remain, it's frequency a function of auto speed - the buzz frequency slowing down as the speed did, and would only stop when the car dropped to about 5 mph or below. Left handers would not cause this noise to start, only rights. Slow turns, no... fast turns yes. Every hard right hander that met the above criterion caused the sound to start again.

I told him about it, and suggested he get it checked out, but apparently he never did.


So, now the car is mine... I've had it for about 6 months. I happened to be in the mountains again, yesterday, and sure enough, same thing. High speed right sweepers - and there comes the sound again - not loud, just noticeable, but there... no change in amplitude in the 4 years or so since I first heard it, so I assume whatever it is, it hasn't gotten worse over the last 4 years/15,000 miles.

Yesterday, I experimented a bit, and could always predict just before it would start - only right hand sweepers, beyond 90 degrees, and only if I was hitting the turns fast (over 40ish) and hard enough to start really feeling the G-forces against the seat bolsters... fun speed, as I would call it. Driving just as hard in left handers (or even harder) does not bring this on. I could slow the rate through right handers, and keep it from showing up, but increase the speed just a bit, and it would show up again.

Again, the only way to make the sound stop is to come to a near halt - no gear changes, left sweepers, or anything else will make it go away - just slowing down below 5 mph...

Okay, sorry about the long winded novel, but this is so unique to my long experience as a backyard mechanic that I thought a good description might help.

SO, has anybody ever experienced something similar, and/or have suggestions as to the cause? I'm not getting anywhere with JTIS, relative to the makeup of the differential - is it a standard type or a limited slip? I thought perhaps something winding up in a limited slip cartridge might be the cause... but have no idea with the x308.

I'm not going to lose sleep over this, as it doesn't appear to have gotten any worse over the last 4 years, but I sure would like to know what is causing it.

Any suggestions are appreciated.

QM

 

Anybody have anything similar? Is this a singular occurance? If so, why me, LOL?

 

First off, its an open diff, not l.s.d. have a look at the rear heat shield, is it loose? do a tyre rotation?

 

THanks, I'll look at the shield - I had just done a rotation prior to the most recent drive - don't know how many rotations had been done after my first notice 4 years ago, it could now have the same tire in the same place... but I can't see how it's tire/wheel related since it begins only on the right high speed sweepers, then only goes away when dropping below about 5mph.

 

My first thought was a wheel bearing on the nearside loading up as you sweep round the curve, but you say the noise comes from the middle rear. Does the XJ8 suspension rely on the diff bearings to take side loads ? The earlier XJs used the drive shafts as the upper wishbones so this has to rely on the diff bearings for side loads, (as well as the wheel bearings). I just don't know enough about the later suspension set up. maybe others with "The Knowledge" can come in and put their thoughts.

 

I had a 4-Runner that any time I would perform a rapid stop at the moment it would stop I would feel a thump in the center of the car. I thought it was the transmission mount but that was good. Being the obsessive person I am I decided I was going to find this problem if I had to hang from the bottom of the truck or video and observe what was going on. I checked everything from the front to the rear and it still continued. For whatever reason I decided to look at the front drive shaft and differential and what I found was a split driveshaft that had not been lubricated. I lubed the shaft and the problem went away. When I took the truck to Toyota and they replaced it under warranty. This is a drive shaft that is 2 parts that slip inside each other (I hope that makes sense). When I hit the brakes the frontend would torque and when it stopped it would settle down and lineup properly and I would get the thump. If you do not have a split shaft I would be looking at the flexible jurid couplings front and rear.

 

This is a metal scraping on metal sound, as if I laid a screwdriver across one of the half shafts while it is turning... the strange thing is that it only shows itself through long, fast, right hand sweepers.. and then won't go away again (although its frequency drops with speed) until the car reaches a near stop - no matter how far I've traveled, nor how many other turns I've taken... once below about 5mph, though, it's gone again until I hit another similar turn - high speed, right only, not left... It's got me stumped.

 

Quad,

I hear what you are saying and not sure what to offer other than my left-handed theory. I am thinking that the torque of the turn and body shifting that the center hanger, split shaft (if you have one) or the coupling could be binding. If it is not what you thought it should be then try what is not logical. The other is internal to the Diff. Drain the fluid and look for shavings.

Whatever you find please tell us!

 

You can bet I will, once i do find it... Nothing wrong with left handed theories - they're better than what I have right now! And the possibility of torque induced binding is not far fetched.

I'm not going to be in any hurry on this, it's been there for four years with no change... I don't expect I'm on the edge of catastrophic failure. I will try to get it up on jackstands this weekend and do some investigation around the area. I'll report in if I find anything. Thanks for the help.