Transfer Case Damage

[mills_88]

So I have pulled my gearbox and transfer case out to try and get to the bottom of this knocking/grinding noise on deceleration. Upon opening the transfer case I noticed a fair bit of damage and a lot of hairline cracks in the casing.

It appears that something is loose/out of alignment and is allowing the pinion and ring gear to hit the housing and each other. As you can see there is some serious chunks missing out of the teeth, parts of the housing and evidence of scuffing of teeth against housing.

Anyone come across this before, I am guessing I'm up for a new case but I would like to know what actually went wrong to cause this? All the bearings seem good and everything is tight with little in the way of play.

I also noticed the outer race of the angular contact bearings that support the ring gear are rotating in the housing as well. I'm guessing they shouldn't be doing this?

Anyway photos:

 

[naughtika]

I don't think those are hairline cracks, I think they're like that simply because its a cast aluminium..

about the obvious signs of scratches, check the bearing and see if there are breakages in there..


is there alot of movement/play?

 

[mills_88]

I was thinking they might be normal casting cracks but not really a pro at this type of thing. In terms of movement, no there is hardly any.

I haven't got access to the pinion bearings yet so that will be the real tell.

The scuffing on the machined surfaces also worried me since it would suggest things are moving around when they shouldn't.

And if you haven't already, you can see damage to the base of the gear teeth on the edge of the ring gear. There is also damage on the outside end of the pinion.

 

[vvr4]

ive got a spare complete transfer case with gearset if ya interested, pm me cheers

 

[mills_88]

I might take you up on that, not convinced the transfer case is the problem but wouldnt mind swapping it out to eliminate it.

How much do you want for it? PM me.

 

[Size1]

doesn't look good. Definitely unwanted movement in there. Outer ring of angular contact bearing has to be a press fit. You can get a rocol crack detection kit it works really good. Three aerosol cans, use it regularly but never hsd to pay for it , cant imagine it costing too much. If you do get another transfer case and you want to get rid of this one let me know. I would love take a look at it.

 

[king_panther]

ive got a spare complete transfer case with gearset if ya interested, pm me cheers

How about paying to become a member & starting a proper FS thread in the Classifieds section ??

 

[mills_88]

Sorry, my bad for encouraging non member selling there. Not looking at buying another just yet anyway, going to see how this one goes back together first.


The thing with that outer bearing race is that it is not moving axially, so would be supporting the angular contact nature correctly. It just spins freely, I still havent had a definitive answer as to whether this is a problem from the many people I have asked.

 

[mills_88]

So after really having a good look at this again, I don't think the "machined looking sections" have been caused by gear tooth contact. I think it is more likely they have been there from new since there is no way the teeth could have hit some of the areas. Therefore the only real "damage" I can conclusively say shouldn't be there is the damage to the teeth.

Now this damage to the root of the teeth is only present around 180 degrees of the ring gear which seems weird. The other thing to note is that when I drained the oil out of the transfer case I only got about 200-300ml so it didnt have enough in it.

Is it possible the noise I was getting was the gears meshing with no lubrication and simply putting it back together with proper lubrication would get rid of the noise.

I'm seriously running out of ideas diagnosing this noise I'm getting.

 

[naughtika]

from memory there should be around 700ml of fluid in there..

once damage is done on the bearing, re-lubricating wont fix it permanently, it might fix it for a few weeks but the noise will come back..

 

[mills_88]

That was my understanding but there is no damage to the bearings from what I can see. Generally bearing damage is pretty obvious.

I was expecting to find something obvious making this noise and I haven't so now I am genuinely considering putting it back together till something actually fails so I can figure out what is wrong.

 

[Size1]

If the noise was due to a lack of oil there would be wear on the gears due to higher concentatrion of contamination from wear particles becoming abrasive. This also contributes to rapid deterioration of the gear oil due to higher temps. Abnormal wear patterns would be pitting, spalling, and galling and in extreme conditions plastic flow. These would be caused by contaminated, low or no oil. Fatigue can be caused by cyclic stressing due to high or intermittent loading.The tooth breakage could possibly be due to a stress riser from a quenching fracture which from the looks of it is wuite plausible. Being an inherent fault there would be nothing you could do to though. It is bit hard to diagnose the failure just from photos but google the symptoms I have outlined and compare the pics to yours and you should have a good idea though I dont think it is from low oil. As long as 1 3rd of the lowest gear is submerged it should be ok. Hope this helps.

 

[mills_88]

No there is no damage other than the loss of material pictured. This one has me stumped. I'm leaning back towards universal joints although there is nothing too out of the ordinary there either.

Possibly bad engine mounts causing uj's to bind.