Failed Diff, Hmmm...I think I know what happened...
 

Eaton tandem real axle-differential - front differential of the tandem set has failed after 78,000 miles. The pics are of the pinion gear and the ring gear. Both gears have suffered catastrophic failures. Reviewing the pictures shows that both gears appear to have suffered stress fractures leading to failure.

What do you guys think caused it?

http://forums.pelicanparts.com/uploa...1289603146.jpg
http://forums.pelicanparts.com/uploa...1289603169.jpg

sorry for the lack of quality of the pics - customer sent them in. I was hoping for the actual parts. I hope to get them in over the next week or so.

We went through a period where we had failures that look exactly like that in our 935 clone with a G50 box. We set the r&p according to Porsche procedure, and broke three sets in a row. Now those were very short track outings..

On the next build we said eff the Porsche set up, and got out the Prussian Blue, and set the r&p by eye, and have not looked back..not a failure in...going on five years..

Looks like a set up failure, was that box rebuilt recently? Or to much power beiing passed through the box...

Dont' think its a failure due to lube..

Also doesn't look like heat was a factor.. no bluing etc..

How much experience does the driver have?

I would be wondering if some sort of shock load was applied to those gears, maybe driver starting out too hard, and lurching the truck, or maybe stuck and and trying to rock it out. Or set up with too much backlash.

Hard to tell from the pictures but i'll guess driver abuse.
40k lb or 44k lb rears? Either way it takes a lot of torque to twist the pinion teeth off.
I think the damage to the ring gear is from the pinion coming apart.

they used snow tires?

Overloaded axle + shock.

I'm guessing bad gear oil... ;)

looks like some fast food got caught in there and "broke the metal"

What happens over time if you haul your car on a trailer and strap it down through the wheels instead of the body frame..

The only time I ever saw anything like that the preload on the pinion bearings had loosened way up, and there was a rodeo clown involved.

Too many bolt-on upgrades without any attention to the drive train?

Can you give us the make and model of vehicle? That would help understand if it was something like I mentioned above or an overloaded bread truck.

Close but not quite.. I think it may even be an urban legend..

That is if you strap your car down by the wheels, and leave the transmission in gear... I have heard about these failures, but have never seen one in person..

BTW I strap my car down by the wheels.. lets the suspension work..

Someone (our driver) did something like this trying to drive with the parking brake set. Ripped the pinion right out of the diff. I thought the drive shaft would have failed first.

I didn't know you were supposed to put the Cool Collar in there...

One too many burnouts....

JR

hahahah

<object width="480" height="385"><param name="movie" value="http://www.youtube.com/v/UcSaXmXQ3yc?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/UcSaXmXQ3yc?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>

<object width="640" height="385"><param name="movie" value="http://www.youtube.com/v/ty0WGrj5hHc?fs=1&amp;hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/ty0WGrj5hHc?fs=1&amp;hl=en_US" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="640" height="385"></embed></object>

Gear oil with the new tungsten shot additive ?

Multiple red line clutch drops with no tires on?

Do tell.

Incorrect pinion depth setting, I once ruined a rear end by not crushing the collar correctly. It was not in a semi though.

That's an easy one. Take a look at the damage on the ring gear. No where near where the load is supposed to be.
Something got distorted or out of whack to the point were the load was no longer transferred to the center of the gear where it belonged, instead it was transferred to the edges of the teeth where it shouldn't be.

The failure did not start with the gears, they are the result and not the cause.
My bet is either a bearing let go or some other mechanical failure which resulted in a significant misalignment of the gear mesh.

The rear tandem lost traction while the front took the full force of the load. The drivetrain wound up, unwound, would up again then BLAMO!

Wow - you guys are good! Two camps here: 1) Driver Abuse 2) Bad Set-up

Very good! Now, if you believe it is one, prove the other wrong and if two wrong prove the one wrong!

I am of the belief that it is both 1 & 2! (but not the gear oil!!!)

Really hard to tell from the pictures.
I've seen some idiots trying to slide their trailer tandems and it's a wonder the driveshaft doesn't get bent like a pretzel let alone what it does to the rear end and U joints.
I've never had a rear end fail. I replaced mine(2 years ago) at over a million miles because the nose bearing had loosened up enough (frt. rear) that i couldn't keep a seal in it. I wanted to change the ratio anyway so i swaped out both rears at the same time.
If there was no flaw in the pinion i still say driver abuse.

Kind of like aircraft accidents and fire investigations, I'm right because I said so and it's always pilot error.

Naw, I wouldn't say driver abuse, I'd say rookie mistake.

He who has the best technical rhetoric wins :D

+1.....This is also my vote
And I agree with Sammy (rare) that the gear wear pattern is the result, not the cause.

Bad lubrication? :)

Wheel hop and other driver mistakes usually damage the axle shafts, not the R&P.
Now if an axle snapped and loaded the diff with debris, you could have significant R&P damage.

If the axles are not damaged, I say to check the R&P setup. Either it was a bad setup, or as speculated in another post, a pinion nut or bearing failed and allowed the pinion to drift out of proper mesh.

Those are my guesses.