Thread: Gearbox bearing damage...

The case hardening of the bearing surface has degraded, but only in a very small section of the surface. Ive pulled the bearing it runs on, and the rollers are unmarked and clean, so im a little confused how its done this damage.

This gearset is ex EVLNXR when it was turbo, so has done some serious work in its life, but the gears and other bearings still look fine.

The old gearset was a 3.8, but i have the 4.1 set that came out of this case that i will be putting in, even tho i have another 3.8. The 4.1 is immaculate, and came from a GTI pulsar at stealapart with 80k on the odometer, but had major 5th gear popout and the synchro ring was totally flogged, easy fix tho.

Im hoping the 4.1 will give better gears for the hairpins at Taupo, 3rd on the old box was a bit taller and it lugged out of the corners a bit. All gears but 1st are shorter in the 4.1 box.

weird... what box did the 3.8 come out of originally?

It looks as if you caught it early. It is my opinion that the hardened shaft end starts to get pitted and chipped in one area, then eventually the hardened material keeps chipping away in both directions around the shaft until its all destroyed. Check out mine!

more than likely caused by dirt or metal shavings in the oil. A bearing that is nice and sold doesnt just deteriorate like that for no reason unless there is slop in the bearing, But even the slop is caused primarily because of dirt or shavings.

Yeah, i heard the noise develop quite quickly, got a trackday in feb so figured it would only get worse, only took 1.5 hours to remove it and get it apart. The oil was all quite clean with minimal shavings on the drain magnet, and the bearings are all shiney and unpitted, so going to put it back together with a new gearset and hope for the best.

Oh, its a w11 avineer engine with t28 going thru it. Old engine was around 350whp, this one maybe 230whp ish.

You might consider replacing the bearing as well even though you said it looks good.

this is sorta what Im expecting to find once Ive stripped my box apart, would a shaft with similar damage to that be ok in a new bearing? or is it just a case of try it and see?

Def want to replace the shaft, its koozed.

I didnt have an option for the bearing, had a big cleanup like a week ago and threw out a couple of spare cases ive had for 5 years... typical.

I pulled the rollers out of the bearing and inspected them all, no damage whatsoever, and the shell was clean and undamaged, so i'll have to cross fingers for that one.

On a side note, its the tightest VLSD center ive ever had, i was actually curious to see if it was stock, which it is , as its so good on the road.

I see this alot in my line of work. There are usually a few basic reasons of how this can happen:
1. Spalling or Brinelling. which is caused by excessive torque loads. What that means is that the torque load has overcome the load that the base material is rated to handle.
2. Simply the lack of proper lubrication to the bearing.

most likely it is the second option. i am saying that because i know our trannys can take more that what you guys are putting to it and still have no wear at all.

To fix this we use a spray metal process to build back up the shaft and then machine it down to the proper size. usually the spray metal is stronger than the base metal.

Lance, What kind of machine do you use to build the metal back up specifically? Curious about that.