Ok so after replacing the inner and outer wheel bearings on both sides, the passenger side still makes that rattling noise (drivers side is fine now)! Is there anything else that could be doing it? Everything is tightened down, so the bearing shouldn't be shaking around... HELP!

 

maybe your ball joints are worn?

if you jack up the front of the truck, is there any play in the wheel?

try just grabbing stuff (wheel, cv, etc.) and moving it around with the wheel off the ground and see if you notice any excessive play anywhere.

also, you say everything is "tightened down", but you can over tighten wheel bearings...did you adjust the pre-load as per the FSM?

(you tighten the adjusting nut to, iirc, 40-something ft lbs...then back it off to hand tight, rotate the hub foward and backward a few times, then retorque the adjusting nut to some lesser torque--don't remember the number offhand...then torque the locking nut to the proper torque...then check the preload with a spring gauge.)

 

Could also be the spindle bearings, if they're worn the axle could be rattling inside the hub. More detail in these threads:
https://www.yotatech.com/forums/f2/2gen-4runner-screeching-grinding-noise-right-turns-only-47573/
https://www.yotatech.com/forums/f2/rub-moan-squeak-front-end-4runner-please-help-47923/

 

Thanks guys I'll check that all out on Monday... I've noticed that when the wheels are really out of allignment, the noise is VERY loud, but if not you can't even tell it's there...

 

Other things that could cause that rattling in the front end are:
Worn out/missing sway bar end link bushings, and same for the shock bushings.
One time i forgot to fully tighten the engine skid plate, the bolts were only hand tight. It really rattled over bumps! (doubt that it though).
Also, worn out loose tie rods ends could rattle. How's your steering?

 

I think there is also a spindle bushing that can wear out. I think there is a write-up here on replacing it.

 

I've noticed sometimes, and it's getting more consistant, that my steering feels, well, I don't want to say "loose" but feels like it's TOO easy to turn the wheel... However, I'm having issues with my PS pump, so that could be it.

When I took it into the shop for the rattling, they mentioned that the lower ball joints have "play"... Any chance that's what I'm hearing?

Man I really hope it's not the spindle bearing...