How do you know when the rear diff is going out?

My neighbor has an 06 taco 2wd with 68k. Its an acces cab TRD off road with electric rear lock. He has been complaining about vibes at about 1800 rpm's and he says his truck shifts funny in low gears. I test drove his rig and it does feel funny. It's like the rear locks up a little. Hard for me to explain. Anyways, his check engine light is not on, and no codes came up. He took it to toyota and they found nothing. He says he recently hit his axle on some curve. I checked it out and there is a ding right at the ball but nothing huge. It was just pushed in about 3 centimers. So here is the Question, how do we know if his rear diff is bad?

 

Is it grinding? Have you drained the oil to look for metal shavings and/or metal slush? Also inspect the gearing itself for wear. A little is to be expected at 68k... but shouldn't be much at all.

It sounds the fairly normal jitter for these. There have been improvements altering the drive-shaft angle, doing a good lube job (probably needs it), some had better luck with a single piece shaft as well. Also.. check tire balance, tread wear, all the suspension components like CV joints for wear and rips too.

Unfortunately vibes can be a lot of things.... The comment about being 3cm pushed in on the "ball" (what is this, are you talking the pumpkin on the diff?) is a little concerning though.

 

Well right before my friends went out we herd a ticking sound like something was moving around then the next day it locked up on him in the middle of traffic.

 

yea that's exactly where it is. I can take pics of it tomorrow and show it to you guys. We actually did the diff fluid and all looks normal, no grinding. How do you change the angle on the drive shaft, or make it one piece. This is this guys work truck and he's a pool boy so he needs it running well.

 

Take a pics please. Now if it is really pushed 3 cm into the diff housing at the place where third member mounts you may have a problem since there is not much space there between the housing and the ring gear. Once you post pictures it will be better to asses but if it is exactly under the ring gear then it is possible that ring gear is rubbing the inside of the housing. Solution to that would be to remove third, and hammer the ding out before ring gear explodes and does much more costly damage.

 

LOL. Man i was way off! He had it fixed this AM. Appearantly it had something to do with his rear shocks/suspension. MAJOR FAIL!