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AR15.COM
9/4/2008 9:45:54 PM EDT
Got a 2000 Tacoma 4wd 2.7L with 140ish k miles.  I've been running synthetic gear oil in it since I bought it.  Today I drove it to work, no big deal.  I went out to drive to town for work and felt some terrible clunking and lurching from my truck.  I got out and noticed my front hubs were locked, thought that was the cause of it.  Commenced to driving and it kept happening....

Ended up draining the rear diff and noticed the fluid was silver/gray from all the particles in it and the magnet had a ton of metal on it.  Heres a pic of the damage, both side gears are ground up real bad.
carnage

My question, what causes this to happen suddenly? I don't do much offroading really and only had about 10k since my last fluid change...

9/4/2008 9:53:23 PM EDT
[#1]
I'd say bad luck.  Really no easy answer for you.  It just happens.  I'm sure it's not caused by the synthetic fluid or your maintenance habits.  Could be metal fatigue, age, hard to really say for sure.  


Was that the front diff or the rear?  If it was the front, why were your hubs locked in, anyways?  Someone screwing with you at work?  Locked front hubs on an open diff shouldn't really cause that type of damage, unless it ran for a loooong time like that.  It would cause more wear from everything turning, but really shouldn't cause that.

Duh, I reread your post.  Locked front hubs won't do that to the rear, but make sure your hubs are unlocked next time to get to work, and recheck before you leave.  
9/4/2008 10:10:54 PM EDT
[#2]
Yeah I think some of my soldiers screwed with me on the hubs.  

I really thought it was the front making the noise.  Had already started breaking it down and decided to troubleshoot it again and I noticed th rear was making the noise.  Of all the things to go wrong on the truck I'd have never guessed the rear diff.
9/5/2008 6:01:46 AM EDT
[#3]
I had one do that on Bronco. Was driving fine. Went to do a u-turn and the rear exploded. Funny part is, I was able to drive backwards about a 1/4 mile to the house. Wouldn't go forward but it drove slow backwards.
9/5/2008 6:29:37 AM EDT
[#4]
Looks like the ring/pinion are ok but the spiders are toast? That is odd but stranger things have happened. Is there a shim or crush washer that could have disintegrated and allowed the gear mesh to be way too tight?
9/5/2008 6:39:01 AM EDT
[#5]
Probably fatigued from cold/hot cycles, you do live in AK correct? Are you sure that the fluid level was correct and not low?
9/6/2008 7:54:47 AM EDT
[#6]
From the pics it looks like the spiders gave up the ghost either bad or incomplete heat treat causing the to wear. I'm sure you will find a few teeth worn almost through allowing the others to climb and dig in to each other.
 If the R&P are on good shape, none of the bearings are pitted etc.  Flush the 3rd member replace the spiders
9/6/2008 11:35:41 AM EDT
[#7]
I looked at it some more today and when I spin the input shaft the spider gears spin the same way (as if it were a locking diff) It looks like the gears slipped a little and tooth is hitting tooth dead on.

Waiting on my lockright to get here so I can install it.

Yes I had the correct amount of fluid.
9/16/2008 4:36:42 AM EDT
[#8]
If the splines are bottoming out on each side of the gear set, its sending shock waves into the metal causing excessive wear and tear. Kinda like beating on it with a hammer. This action also exerts lateral pressure on the bearings and carrier. Inspect it very closely for hairline fractures