Latest victim of the 348 gearbox curse

My appologies...I have never seen any good fluid that looked like that. It looks like water and oil but if that is what it looks like out of the bottle it must be o.k.. Those bearing look eaten alive. They look under lubricated with heat breakdown or grit in the oil increasing wear. At a full 26K miles of wear on the bearing I can't imagine modern metal bearing fatigue at that rate unless there is another problem. I guess there is a possiblilty of too much load for that bearing design I just don't know the math. But I can't imagine our tiny 300hp motors having enough to destory these 4 large bearings. But you certainly have a case. A whine by the way is improper gear mesh. So if you have it there is slack in the shaft positions and gear relative to one another. This can happen with either bearing destruction or loosening lockrings. The controversy as I see it is which comes first chicken or egg? Bearing destruction or loose lockrings? Based on other bearing loads I have seen with this size bearing I vote for loose lockrings. This issue IMO is alot like the battle I had on the loose lugnuts thread where people wanted to use ferrari oem spec on lugbolts but had lugs come loose. I said they fastener can take more torque based on standard industry charts of torque vs. fastener size. I said just up the torque and the bolts won't come off. People got mad at me for saying that. Well it has worked for my lugbolts and for my gearbox too. I'm just a billybob.

 

The controversy as I see it is which comes first chicken or egg? Bearing destruction or loose lockrings? Based on other bearing loads I have seen with this size bearing I vote for loose lockrings. This issue IMO is alot like the battle I had on the loose lugnuts thread where people wanted to use ferrari oem spec on lugbolts but had lugs come loose. I said they fastener can take more torque based on standard industry charts of torque vs. fastener size. I said just up the torque and the bolts won't come off. People got mad at me for saying that. Well it has worked for my lugbolts and for my gearbox too. I'm just a billybob.

Maybe...and No.

 

There's the BillyBob we all know & love.

I tell 'ya what man... When I talked to you about rebuilding this for me, I should have just stuck with that plan. Look at this!(this thing was really stuck in place)
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Underlubrication?! Wouldn't that leave mirror finishes instead of pitting?

 

Hey Daniel, you've got me on the "thick splined clutch shaft" part. I don't know anything about that sort of failure.

...but, the bearings on the pump failing...that's a different story. He's got clear pitting on the bearing balls and race there.

Why?

My guess?

Sand (OK, silica) from the OEM casting process is leaching out of our gearboxes over time.

Don't change your gear oil every year? Then you'll get sand in your tranny fluid...which if driven enough will pit your bearings/races and lead to tranny failure.

But that's just my guess.

Some pros have weighed in on the matter, though: http://www.mcnallyinstitute.com/05-html/5-3.html

 

LOL! you would not have to work so hard if you had this....
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How about this one?
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Looks pretty well worn!

Is that caused by burnouts?

 

SKF weighs in on pitting: http://www.alliedbearings.com/downloads/skf_bearing_failureandcauses.pdf

 

This is from 1993 on a 1991 348 around 30K miles

no burnouts... factory did not stake the ringnut at all! Finally it came loose gear clashed GB went kaboom!

 

I know chubby doesn't agree with me but I still say its the bearing cage that is the cause of this problem. It just can't handle the lateral pressure that's placed on it. I will say though that I have seen the ring nuts that haven't been properly torqued down, but this was on my hub axles. Having said that I DO NOT put it past the guys at the factory to not stake the ring nuts on the main or lay shafts, or put enough torque on them. But more over it has got to be the bearing cage that just can't handle the pressure. The bearing race that came out of my gear box looked almost the same as Michael's. You even saw it chubba.

 

The right tool makes life much easier!!

 

Here's what SKF says about inadequate lubrication:

 

Here's what SKF says to expect to see when you have lateral pressure on the bearing:
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SKF on axial load flaking failure of bearings:
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Yup!

And that is just what Michael's looks like, and what mine looked like. So we need to find out what bearing we can use in place of the standard one. Like I said before I thinking that the 355 bearings will work. All we have to do is make sure that the dimensions are the same.

 

We need to make certain that the cause of the failure is lateral overstress if larger bearings are the solution (going too large in a bearing can cause problems due to a lack of pressure, as well).

Keep in mind that the ball bearings were pitted, not just the race/cage. If that's from sand (leaching out from our OEM sand-casted tranny housings per my theory) then bigger bearings won't be the answer (instead, the answer would be more frequent gear oil changes). Bigger bearings will fail just like smaller ones if the problem is contaminated fluid.

Anyway, I posted both...could be your theory...could be mine...could be both. If it's your theory, then we need to see the bearings that Ferrari used in their tranny gear box pump update circa 1993+.

The breakthrough is that Michael B posted his pics when catching just the bearing failure...with nothing else having failed in his tranny (so we can therefor rule out all other possible tranny failure modes such as a non-bearing part breaking up first to only later cause the bearings to fail).

Based on his experience, combined with your bearings looking like they had the same damage (ditto for ReinerKaiser et al), we should be able to say that it *is* the bearings that are failing first, not some other tranny part.

Well, did the bearing in question fail because of lateral overstress (possible, but no metal fatigue cracks in the photos) or because a common contaminant is pitting the ball bearings?

 

Check with reiner. he is having some custom bearings done due to poor availabilty of this skf part# and possible poor load bearing ability like you claim.

 

Anyway, if it *is* sand from our sand-casted OEM tranny housings leaching out to cause the pitting, then we should be able to see sand pitting in other tranny areas such as in between meshing gear teeth areas, correct?!

So if there is sand pitting in other areas of the tranny, the answer to the gearbox curse is simply more frequent fluid changes.

...and if we *don't* see that pitting anywhere except on bearings exposed to high axial overstress, then the solution would be either larger bearings or bearings with more balls (don't go there!).

 

I talked to him already. He was supposed to give me the number off the race, but I haven't gotten it from him yet. There are two shops by me that I have had pretty good luck with in the past.

 

Tapered roller bearings.........trust me.

 

Perhaps you've seen some standard bearings replaced in situ on your mining heavy equipment with tapered roller bearings that then went on to withstand large stresses and have long lives??

If so, then I vote your way.

But I'd still like to verify that Michael B's tranny shows *no* other signs of sand pitting, though (just to be certain that it isn't contaminated tranny fluid causing the bearing failures).

 

I have seen it all ND.
Also, I actually reckon that Michael B's failed bearing pitting, was due to the load placed on the bearing causing the hardened surface on the balls to flake away into the race, which caused a snowball effect on the rest of the balls as the hardened flakes crunching away in the bearing caused this pitting on the other balls and race.
I hope you guys understand what I just posted. It is a little hard to explain typing it, but I think you guys are well aware of what I mean?
I have seen this before MANY times and I think its whats going on here. That is the only reason that only this bearing/part in the gearbox is like this. All the fine bearing material usually ends up in the pan on the magnetic plug and gets dumped every oil change. This does not happen overnight. The bearing could flake away and do this for years leading up to its failure. Sometimes, you can catch it early and replace the bearing before it turns into a catasphrophic failure.
Thats what I reckon anyways and I reckon that a tapered roller bearing is best suited to handle the load placed on that paticular bearing.

 

http://www.marks4wd.com/products/split-t-case/lc-tc-trb-conversion.htm

 

Cheers ND!!
I just ordered a set for my own 75 Series L/C trayback.