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Loud roaring / grinding on acceleration only.... Noise from the rear axle



back story>>> I recently purchased a broken 1996 Tacoma Extra Cab 4-wd (175K).





After repairing the left knuckle / tie rod / CV / brake line / strut from associated damage (ball joint failure / bolts backed out), I then was able to take my first drive. Immediately I noticed that the rear end was howling VERY loud (cant drown it out with the stock radio kind of loud).

So is it bad ring and pinion or U-joint... ???

I pulled the drive shaft and it looked dry, not greased, but not too bad. Rear pinion has a beard of fresh gear oil, never a good sign, but usually just a plugged rear axle vent causing pressurization / relief (as the axle heats up) through the pinion seal. Both rear end and drive shaft look abused / no service. Back lash is a little excessive but not uncommon for 175K. Pinion bearing stilll feels tight.

Later a second inspection of the drive shaft revealed the rearmost joint at the axle was a little stiff and might have a slight bit of play (neither are good). New Moog super duty U-joint is only $25. Koyo / Matsuba are the preferd brand ~ but at 8pm Friday night Moog will do just fine.

I pulled the old joint down to find this.... V V V V V V V V V V V

Looks like the needles got dry and began to wear. The diminished size turned them sideways slightly and they then became more of a bushing than a bearing. Ribbed / 30 spline U-joints are bad. This noise could have been amplified by the drive shaft tube mimicking a bad gear set. Will find out tonight if this was the only issue.

 

Noise is gone! The roaring / grinding on acceleration was the rear u-joint.

Further inspection of pinion with drive shaft installed reveals that it does have slight lateral play. This will need to be addressed but so far it is not a deal breaker. Hope to measure it soon with a mag base dial indicator to quantify the number.