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Discussion Starter #1
I have a 2012 regular cab 4x4 5 speed Tacoma. Original owner, 42.5K miles.

Cooper AT3's 265 70 16. Stock Steel wheels no spacers.

Bilstein 5100's:
Fronts set at 3rd lift ring @ approx 1.75" lift. No diff drop (Yet)
Rear has Wheelers 3 leaf progressive AAL kit and 3 degree pinion shims @ approx 3" of lift.

Had it realigned at a local Toyota dealership after I installed the lift over 20K miles ago. Steers straight, rides and handles normal.

PROBLEM & SYMPTOMS:
Recently while in 2WD in 3rd & 4th gear between 35-45 MPH there is a droning low frequency noise that occurs every 5 or 6 seconds lasting about 5 or 6 seconds. The noise does not seem to be cyclic with the rotation of the tires. When the noise is audible I feel a very slight vibration in the steering wheel that seems to be coming from the front left of the truck. Also note that the noise and vibration almost disappears when in 4WD.

I jacked the front of the truck up for a inspection of the steering & suspension components letting the suspension droop. The only thing I can find is that the left front CV ( or bearing ?) clicks when the tire is rotated, and the inside edge of the front left tire is cupping. The outside edges of the drivers side and passenger side front tires have always cupped on all my Tacomas I have owned, but never the inside edge of a front tire.

Does any one have any idea what is going on or going bad/wearing out ??? :dunno: Any and all comments are welcome ! !!

Thanks !
 

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Discussion Starter #5
Update

Local Dealership is doing the TSB under the drivetrain warranty.

Had to go back a 2nd time to get it diagnosed. The weather was above freezing the 1st time I went, 55F, so the noise/vibration would not repeat consistently enough for the technician to be able to agree on the problem. 2nd time I made sure it was going to be below freezing and it was consistent.

Parts are on order with the NEW TSB bearing part number so hopefully it will last !:smile2:
 

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Discussion Starter #6
TSB Completed Update

Well the TSB repair is done. Bearing has been replaced with the revised part #.

Here here are the symptoms now: The variable pitch droning noise is gone at all speeds. But there is now a louder constant droning noise at lower speeds between approximately 20 to 35 MPH. There does not appear to be any droning noise at speeds higher than 35'ish MPH.

My breakdown of what is happening now: With the new tighter tolerance bearing installed there is now a constant droning noise at lower speeds because; the shaft is spinning slower and the bearing has more load on it at the 6'oclock position on the outer edge, and more load on it at the 12'oclock position on the inner edge. As the shaft spins faster the noise disappears because the load becomes more evenly distributed on all the needle bearings.

My breakdown on what was happening: The old looser bearing made a variable pitch droning noise from a starting roll up to approximately 45MPH because; there was excessive slop between the needles and the shaft causing harmonic vibrations to occur thus making the variable pitch droning noise. The variable droning noise would disappear at higher speeds above 45MPH and turn into a constant droning noise as the shaft spun faster and the load became evenly distributed on the needle bearings thus causing the harmonics to disappear.

So what dose all this before and after breakdown mean to you. Basically the new TSB bearing is just a band aid fix to the root of the problem which is the slop between the spider gear and the carrier. The slop shown here on this video: https://www.youtube.com/watch?list=P...&v=BOvoM5irtEc

My last words and take on this is to buy and install the ECG supply bearing kit if you can afford it. While the slop would still be there the ECGS bearing is the best remedy as it tightens up the slop best. I went with the TSB repair because I am unemployed now and it was free.
 
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