Broken teeth, front differential

[bobshem]

My 2002 Tundra (V8, auto, 4x4) has a trashed front differential. The vehicle has only 77K miles and the differential gear lube had been changed twice during that time with Amsoil Severe Gear lube.

I can't recall anything happening that could have broken gear teeth but that's what my mechanic found.

I heard some clunking one day. A few days later I heard a fluttering that indicated that the clunks weren't just a fluke.

Now I need a $1500 rebuild.

What could have caused this type of failure? My mechanic is surprised as he believes the front differentials on Tundras to be "bullet proof". The fluid was full and the seals were perfect. He's stumped as to the cause of the failure.

Any ideas? Thanks in advance.

[Herbicidal]

I grenaded my front diff about 6 years ago on an off-road trail. I did not have a locker of any kind and the right rear tire was slipping and so was the left front, I backed up slightly (on an off-camber hill) gave it some gas...the tires started slipping and spinning and suddenly the left front grabbed traction and KERWHAM! Sounded almost like a gunshot. The spider gears in the front diff blew up. I still have a small baggie in my glove box with all the busted teeth in it as a reminder. I was fortunate to have the front diff replaced under warranty. Several years later, I installed an RCD lift along with 35's. I regeared to 4.88's, but before putting the new gears in, I had them cryo'd for extra strength. Someday I may put an ARB air locker up front and bye, bye spider gears! They are the weak link and are not bullet proof. On the 1st gen Tundra's they are basically gears from a Tacoma. Not strong enough for our heavier, v8 trucks.

Back to your truck, could you have been engaged in 4wd and turned tightly on pavement? That would have bound up the front end and potentially broken some teeth. Or like my situation, spun the front tires and then suddenly have one of them 'grab'? If one tire spins like crazy and suddenly stops, that could damage the teeth in the spider gears as all that rotating mass grinds to a halt. Just my .02. I'm sorry that happened to you.