Carl.brooks

Hey guys, I need some help with my cherokee. It's a 2000, 4.0, sport, automatic, and stock. I recently started having a really high pitched squealing sound which I believe is coming from the front but not 100% sure. It sounds almost metal on metal sound. It starts once the jeep is warm and only when I go 10 mph and over. The pitch never changes, no matter the speed or RPMs. I am a God awful shade tree mechanic and have just been throwing parts at this thing hoping I guess write. I originally thought it was a pulley, changed all of them except the alternator and power steering and still hear the noise. I changed the belt, no different. I then went down my driveway, put it in neutral and turned it off, traveling about 30 mph and heard it loud and clear. This leads me to believe it cannot be a pulley or belt (correct?) Soon after, my brakes locked up on me and thought I finally found the issue, replaced ball joints (2 were bad) axle shafts, u joints, wheel hubs, calipers, rotors, and pads, and I still have the same noise. The squeal continues at same pitch even when braking and in 4 wheel drive. I flushed my transfer case and changed the diff. Fluid. I am all out of ideas now and would really appreciate some help if anyone has an idea. Also, not sure if this is related (highly doubt it) I also have an EVAP issue, it is throwing a p0441 code. Any help would be greatly appreciated!

PatHenry

If the squealing happens without the engine on, it's not related to the engine or an accessory.

What I would do is put your front axle up on jack stands and spin the wheel while listening at the front differential with a mechanics stethoscope (available at Harbor Freight for <$10) and at the transfer case output yokes.

What you describe definitely sounds like a bad bearing (squeak/squeal/grinding sounds). There are several bearings that you haven't mentioned replacing that are moving when the tires move:

Pinion bearing. Located in the differential housing where the driveshaft connects.
Carrier bearings. Located in the differential on each side of the carrier (the big gear assembly).
Transfer case output shaft bearings. Located in the transfer case where the driveshafts connect. The front one has a yoke where the driveshaft is bolted into and the rear is a splined shaft where the driveshaft can slide front/back (aka a "slip yoke").

Any or all of those bearings can fail. However, of the three, the most common failure is probably the Pinion bearing. Listen for a grindy/sandy sound when it turns which would indicate the bearing is bad. The front driveshaft spins even when running in 2wd, so this bearing is being "used" any time the wheels are spinning.
Edit - also, play in the yoke is a dead giveaway for a pinion issue. Check for up/down and side/side play as well as in/out play. There shouldn't be any movement possible by hand.

You may want a professional to do the replacement of a pinion bearing if you are not confident in your mechanical skills. Proper installation requires some fairly precision measuring and techniques.
If you have a bad bearing in the transfer case, it's practical and advisable to go ahead and just do a rebuild. I'm unsure if one or both COULD be done from under the Jeep without removing the whole unit, but if the unit comes off I'd definitely consider doing at least all the bearings and probably a new chain.

Also sounds are tricky - it's certainly possible that you think it's coming from the front when it might be coming from the rear, so don't overlook the possibility of a rear pinion bearing or rear wheel bearing as well.

Justcruzin

Can you..(or a passenger) take a video of the noise, travel speed..?

97grand4.0

Yeah you could change every rotating thing on the engine all the pulleys, or try spraying oil or something on each one to find a squeaker first, that way you wont have to change every rotating thing on the engine. Write?
Of course if you then find out the noise continues with the engine not running, you can just rule out the engine. Write?

Carl.brooks

Thank you so much, I will get the stethoscope this weekend and see what I can hear. I will also work on getting a video of the noise. Thanks again!