ive got a 2003 7.3L FX4 auto. when im on the highway oulling and i hit the passing gear she downshifts and the rpms jump around 2800/3200 rpms there is this terrible screeching noise. the only thing i can describe it is it sound like nails on a chaulk board.

I got some hints thinking maybe the empellar wheel is loose or out of balance, or the bearing is going. Truck is pretty well serviced. no mods but an K&N oem replacement. but the truck feels tired and im only getting 12/13mpgs if im lucky.

my only mods are:
warn manual lockin hubs,
K&N OEM AIR,
2.5 leveling kit,
bilstein 5100 front/
fac ranchos on back.
factory exhaust
new ICP sensor
213K miles ....

 

Have you checked the tension on your belt? when they slip the sound like that.

 

belt in brand new and the tesioner is pretty tight it still takes two hands to get it over enough to get the belt off. but i going to say thats not it. ive been raw hidin the truck to day to try to get it to happen again with no luck and as soon as i hit the interstate 10 and went to pass some one at 70 rollin about 2000 rpms and when she down shifts rpms go to 2800 and it happens for about 5 secs and stops.... weird but thanks if u here anything let me know.. thanks

 

I know this is an older thread, but it might help you still or at least someone else.

It is probably your turbocharger bearing. You need to remove the air intake and see how much side to side and up and down play it has.

If it is worn excessively, it will continue to get more sloppy, until it will start grinding away the compressor wheel and the housing. If you keep going after that point, you'll be pulling pieces from your engine and exhaust if your lucky. If your not lucky, you'll be rebuilding your engine.

Don't let it go, unless you have time and money to burn.

Good luck,

6gentex