Help!! Timing Chain or torque convertor problem?

I have 99 Cherokee with 4L engine. Automatic Trans.

I'm getting a shrill metal on metal sound at high RPMs, just before gear changes. I even get it in park position. Like the sound of brake pad sensors. Obviously it isn't, since it does it when I'm not moving. Anyone have a clue what this is?

When you say, "high rpms" how high are we talking?

Not extremely high, still in the safe zone. Maybe 3500? Right at the peak before the gear change, but only when I accelerate REALLY hard. It sounds like it's coming from the trans area.

Is is a constant squeal, or a squeaka squeaka squeake sound really rapid oscillations?

Definately a "squeaka squeaka squeake sound really rapid oscillations"

Reminds me of brake pad sensors.

Well, there's a couple of things I can think of right off.

First, there have been a couple of threads about loose bolts between the flex plate and torque converter. You can check those by removing the cover between the engine and trans, with the vehicle in neutral and off (chocked and emer brake set of course). You'll be able to rotate the flex plate/torque converter by hand and check the bolts between for tightness.

Second, Ujoints. Sometimes U joints, when they start to go bad, will make noise at higher rpms. You didn't say how many miles, but after 10 years they might need replacing - on my 2000, I needed Ujoints at about 90000 miles and that was when it was only 6 years old. But...Ujoints wouldn't make a noise at 3500 engine rpms, only at higher driveshaft rpms, when the vehicle speed increases.

Engine noise can make a loud noise at higher rpms....I recall on one vehicle (my brother's high performance V8) that above 4000 rpms you could not hear the exhaust, only a shshshshshshshsh noise of the pistons going up and down. This might be what you are hearing, except:

Did this noise start suddenly, or has it been with you all along?

Thanks for the help brother! I read this thread a lot and you seem to know what you're talking about it. I'll check out the flex plate when I get chance. It's definately a high pitched buzzing, clicking sound coming from the trans area when I really step on the gas. It's been more of an annoyance sound I've noticed for two years now and just ignored it. Makes sense that maybe something like a bolt or plate is rattling around under there when the RPM's get high. I had the front U-Joints changed 3 months ago, no change. AT 150K, I really haven't had a single problem witht the Jeep, though. It's a real tank. Thanks for all the help.

Sure thing, let us know how it comes out.....

Thanks. Read some other posts about the Flex Plate and it sure sounds like my issue to a tee. Just an annoying chirping, rubbing sound when I accelerate hard.