Differential Bearing Failed After Only 11k Miles

[Mike]

Last summer I overhauled my 99 Accord transmission that had numerous problem stemming from a failed diff bearing. I posted the videos of that on here/Youtube last year. Now 11k later, I’ve got the trans apart to find the bearing on the other side is pretty wiped out. I know this is specialized experience that few have, but I figured I’d throw it out here. Does it seem like that would be a case of preload too tight, too loose, or a faulty part in this case? It uses a selectable shim to preload, I re-used the one that came in it and got 27 in/lbs of starting torque when I set it up. Spec is 24-40 in/lbs, so I went with the 27..

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[Mike]

I’m rebuilding this unit tomorrow, Installing a Superior/Translab shift kit as well, thought I’s give this a bump looking for an opinion on that bearing failure cause. As it stands, I’m putting it together with another new set of dealer diff bearings unless the preload starting torque is out of whack and I end up needing to order a different shim. I still can get the valve bodies done anyway.

[none]

I’m really jealous. I haven’t been inside a transmission since school. My first thought is that the bearing is missing enough material to cause you some valve body scoring. Your view is much better than mine, so can you see a possible path for bearing shrapnel to get to those valves?

[Mike]

I don’t believe that bearing shrapnel made it into those CPC valves. The filters and screens caught it all except for the ‘dust’ of it. The sticking CPC valves is apparently a problem, which is why I bought the shift kit, because it has “no-stick” CPC valves that are ribbed like a condom. According to the shift kit manufacturer, It’s TC clutch dust that makes them stick.

The bearing is certainly missing a lot of material, but it seems it was all caught by the 2 magnets and the filter.

Like I said, my thing I don’t get is why the bearing failed too soon. I have some solid experience preloading tapered rollers, but haven’t seen anything like this where a recent repair failed.

[John Hugon]

At first it looked like too much preload, but with some rollers not damaged as much as others….I my opinion something was wrong with the bearing especially with one roller missing……… you’re one good Technician and thanks for the video!

[EricTheCarGuy]

Perhaps a preload issue or debris left over from the previous rebuild as suggested. I don’t recommend rebuilding Honda automatics for the DIY. It’s rarely successful. However, you’ll never get good at it if you don’t try. You get better each time you have to take it back out to repair it again though. 🙂 That, or you give up and replace it.

Good luck and keep us posted.

[Mike]

I’m as sure as possible that debris from the first rebuild were cleared out, as every single piece was disassembled and cleaned by hand. I’m running a bigger risk this time because I’m not taking the 4 clutch packs apart or taking all the main valve body valves out in the interest of saving time. We’ll see if that bites me in the ass later, but I think it will be fine. The dusting on all the spacer plates seems to be TCC dust, which the shift kit I’m using is meant to reduce slippage during TCC apply (among other things). This also makes sense, as I could always notice the TCC slip a lot during apply if it applied while I was near/at full throttle.

The big caveat about giving up on my unit and replacing it is that I can only put another faulty transmission in. Regardless of whether it works when I put it in, it’s still faulty and will eventually fail.

This car was bought as a educational platform for myself, as I’m getting to the point where most training and experience I get is not really breaking any new ground for me. This car, having a fundamentally faulty trans, has been working out exactly as planned. It gives me the chance to experience AT failures, fix them, drive it until the next failure, and repeat. I’m sure it will need another repair of some kind again after this, but that’s the idea.

I’m heading out to the shop within the hour to put this thing back together and make a video of it, including shift kit installation. In theory, it should be driving by the end of the day. All growing up, I never thought my life would come to revolve around cars like this. I’ll keep you’s posted.

[Author]

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