When I drive my runner there is a "wah wah" noise. It's NOT a high pitched squeal, it's more of a low pitched faint noise. The faster I go, the faster the "rythm" of the "wah wah" noise becomes. My dad drove it and just based on the sound, he thought it was probably either a bearing or a differential going out. I know that the rotors are warped because when I brake, the steering wheel vibrates horribly. I had a shop check it out and they thought the "wah wah" sound was either tire noise or a differential. He said he didn't find any of the "tell tale" signs of a bad bearing.

I'm about to drain the differentials and transfer case and put in amsoil synthetic gear oil. After that I'm going to do the tundra brake upgrade. Hopefully between doing those 2 things, the issue will be resolved. The "wah wah" noise seems to be getting louder and louder as time goes by.

 

*EDIT*

 

Just ignore them...

Anyway, if your gears really are going out, changing the fluid may not fix the problem, as the damage is already done. Now may be a good time to figure out if you want to upgrade gears. Also, do somethign before a pumpkin grenades.

 

That noise very much resembles a driveline vibration. I have that noise now. It's likely a ujoint getting some slop in it. It could also be that the transfercase output flange needs to be tightened. You'll have to see.

Diff gears are not the problem. When they wear, they whine real bad. You can have a worn pinion bearing which can create slop thus allowing the driveline to vibrate, but that's easily detectable by just grabbing the shaft and seeing if it has play.

If you are unsure, take the truck to a shop that specializes in driveline work, they'll find it.

I should add, I had this problem on my truck when it had 220K on the clock and about 5" of lift. I couldn't figure it out until I regeared. It turned out that the amount of lift combined with a not so new pinion bearing was the cause. Hopefully that's not your case but if it is, again, a driveline shop is the way to start.

Frank

 

i would look toward tire noise... as a tire technician for several years, that was a common complaint from people from all walks of life and all makes of vehicle and all differnt types of tire

 

If the noise coming from the back or front of th vehicle?

 

The noise sounds more like it's coming from the front of the vehicle, but it is kinda hard to tell.

 

get your driveshaft looked at as well. may need to be balanced or the ujoints going bad. Pull the rear ds and put it in 4wheel. Should tell you if its a ds issue or not.

 

wah wah noise is virtually ALWAYS tire noise. they get slightly out of round, (on the front) the alighnement or a loose stearing part creates a werid wear pattern. the sound increases and decreases with speed.

Move the tires to the back (see if its less noticable) or pop a buddies set of tires on and see if it goes away.

do the 99's come with ADD? if so the driveshaft shouldnt be spinning in 2wd

 

I have a button beside the steering wheel that says "rear differential locker" and I have a button that says "etc power" and of course the shifter that lets me go into 4hi and 4lo. Is any of that ADD?

 

I'll put my money on your tires being out-of-round. My 4Runners were/are notorious for keeping the tires balanced and in-round. Rotate them before you do any of the other stuff and see if and how it changes the "Wah Wah".

I'll let the other board members answer the ADD (Automatic Differential Disconnect) question, but I believe that with the ADD, the front driveshaft will only be turning when you are actually using 4WD, it will not be turning all the time. THe CV axles can be moving all the time.

 

I had a front wheel bearing go... sounded similar to what you are describing, except it didn't get worse with time. I've had warped rotors, but never had them make noise... seems like they would have to be pretty badly warped...

 

ADD was a way of disengageing the front axle to keep from spinning all the front end drivetrain. but im fairly shure it was done away with (perhaps about the time of the AWD option, which might be a 4th gen thing) im not up on all my newer yota feature crap.

rear diff lock makes shure both rear tires spin at the same speed.
ect power makes the computer adjust the shift points for "more sporty driveing"

 

So... I have to ask, how does the thing move then? the rear one moves all the time unless it's pulled, which I believe is the one he was talking about pulling, driving in 2WD to test and getting balanced if needed.

 

put it in 4hi and pull the rear driveshaft... front driveshaft still spins, therefore you have front wheel drive.

 

front ds doesnt spin in 2wd, so if you take the rear off and run on front then you know if you have a problem somewhere with your rear ds or the ujoints...

 

jackson could have a point too with the wheel bearing...


OT- hows life Jackson? Long time no talk.

 

I know, read my post again, that's what I said except I meant to say "4WD" not "2WD." my typo. Snap-on was thinking you were referring to getting the front DS balanced.

 

perhaps i missunderstood. i thought they were talking about pulling the front shaft.... which would be pointless if he had ADD as in 2wd it wouldnt be spinning anyway.

but yes to troubleshoot the rear then ya, pull the rear, and drive in 4wd. (which i did for a couple of months while i was sorting out rear end probs on mine)

 

Yea, I knew what you meant, I was trying to joke with you but somebody took it wrong. hehe.