Pictures of Failed Pinion Bearing

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Pictures of Failed Pinion Bearing - wez - 03-06-2012

Here is the cause of the "Jet Engine" sound that my car had. I purchased the car from Florida figuring it had issues. When I received it, I drove it one day then tore it down. The tapered roller bearing was the only thing that was trash. For less than $500, I now have it back together.

Pictures of Failed Pinion Bearing - Scott Collins - 03-06-2012

Excellent! Looks kind of like the inside of a C/V joint gone bad. Ever done this type of repair before?

BTW - welcome to the Forums!

-Scott

Pictures of Failed Pinion Bearing - Monstrous4Banger - 03-06-2012

Any details on the procedure?

Pictures of Failed Pinion Bearing - wez - 03-06-2012

First time for a transaxle. I had someone with more experience around to adjust everything. The workshop PDF is pretty good on its breakdown procedures and diagrams. I also had a spot on the center gears of my <acronym title='Limited Slip Differential'>LSD</acronym>. I flipped them and cut them out to match the other side. Not the best thing to have a used gear match up with new ones but Im not ready to purchase a new <acronym title='Limited Slip Differential'>LSD</acronym>.. Maybe later this summer. It should last until then. I will post some pics of that here in a bit.

Pictures of Failed Pinion Bearing - ds968 - 03-07-2012

Wow, I had a single pinhead dimple on my bearing and it made noise, looking at these photos ( that look like Gen. Noriega's skin complexion ) I imagine the jet whine must have been intolerably loud ?!

Pictures of Failed Pinion Bearing - MB968 - 03-07-2012

One nice thing about tapered roller bearings, they typically aren't used for very high DN values (diam in mm x rpm), and under these conditions they can handle a lot of abuse and degradation before catastropic failure occurs. I've seen a lot of this type of failure during my carear, but I'd have to say, this is as bad as I've seen someone let a bearing get. That bearing had to be making noise for a long time; amazing that they let it go so long. Like your "jet engine" comment.

Pictures of Failed Pinion Bearing - Ryan - 03-07-2012

I know that the reason these bearings fail is because of improper pre-load set at the factory. I was wondering how you determined this load at reassembly and were shims involved?

Good to finally see the culprit in person. Great pics. -Ryan

Pictures of Failed Pinion Bearing - ds968 - 03-07-2012

[quote name='MB968' timestamp='1331097897' post='122834']

I've seen a lot of this type of failure.

[/quote]

Do you mean on 968s, or other on cars' pinion bearings ? To my knowedge there has not been one single "catastrophic failure" of a 968 pinion bearing ever reported, where there was any damage beyond just the noise( as in.. pieces breaking off off the bearing, and destroying the trans, etc..) rather, only theories of what could possibly happen, but no incidents to back that up.

We did have people indicate they drove 10, 20 and, IIRC, as many as 50,000 miles with the noise and nothing ever happened, so in that sense not sure the hypothesis of a catasrophic failure is all that sound. But if you've seen that in actual 968s, that certainly changes things, and would be good to know because there are a lot of folks out there that feel if he noise does not bug them, no need to spend the money to fix it..

Pictures of Failed Pinion Bearing - MB968 - 03-08-2012

Nope, didn't mean on the 968. I first touched one less than a year ago. I spent my carear with a machine tool company. We used a lot of tapered roller bearings in our products, particularly ones from decades ago which we still would rebuild for customers. It was amazing the condition that taperer roller bearings could be in and still keep chugging along. And, I've also seen a few come off front spindles of cars that were making a lot of noise, and again, no catastrophic failures.

If I had the noise in my 968, I wouldn't feel like I had to rush to fix it, but I also wouldn't ignore it, as it could lead to other issues.

Pictures of Failed Pinion Bearing - majsc - 03-08-2012

Wez how many miles do you have?

Pictures of Failed Pinion Bearing - ds968 - 03-08-2012

oddly, my son loved the " jet landing on the runway " sound the car made.. he was insisting it makes the car even cooler than it already is <img src="/forum/images/smilies/968/rock.gif" class="smilie" alt="" />

Pictures of Failed Pinion Bearing - wez - 03-08-2012

My car has 108k miles on it. I imagine that the bearing would have lasted a while longer as I've seen worse. Tapered roller bearings can take some serious abuse. The noise was pretty rough.. I think its funny that the salesman at the "dealer" in Florida stated that their was no tranny noise. I really doubt he ever drove the car. Now I can hear all the other noises the car makes. Torque tube is a lil noisy so it is up on the project list next.

As for the shimming process, thats where I didnt mess with it. I let a friend handle that aspect. He used the PDF workshop manual. He said it was too tight. I cant remember the shims used. The procedure in the manual looks pretty simple but I figured I would get my practice on a spare S2 tranaxle instead.

I also went ahead and put a VDO 150C temperature sender in the housing while it was out. It didnt take much time and $7 for the sender.. why not

Pictures of Failed Pinion Bearing - kwikt - 03-08-2012

I keep eye balling my whiney 6 speed on the garage floor for the past few years. I was hoping you would have done a full write up on the repair. I would love to tackle this........... one of these days.

Pictures of Failed Pinion Bearing - mylz87 - 04-13-2013

Can the pinion bearing problem develop at any time regardless of mileage, or is there a safe zone, say, if a car has 110, 130 or 150k miles and the problem

hasn't developed, its safe to assume it won't ?

Thanks

Mylz87

Pictures of Failed Pinion Bearing - MB968 - 04-14-2013

I don't think you can ever rule it out. Even if the majority of these failures were from improper preload from the factory, others will likely fail with use due to other factors. There are two sides to the story that can cause Hertzian stresses to get too high and cause the type of pitting shown in the pics. One side is that the material properties of one of the members (inner or outer race, or the roller) is subpar. This can be from an improper heat treat of the material, of a microscopic defect in the structure of the metal due to impurities, inclusions, etc.

The other side of the story, if the material prop. are good, is the load becomes excessive for the material. This can happen for several reasons such as initial preload, increase in preload due to thermal growth of the assembly, or excessive load from user abuse, etc. Or it can come from a foreign body getting between the rolling member and the race, such as a piece of hard metal from another member, rust (which is quite hard) due to an assembly sitting for a long time, etc. Anyway, you get the idea. Can't ever rule it out even if you've made it past the initial failures due to improper preload settings at the factory.

Edit: Opps, thought I'd better come back and make sure this info was kept in perspective. So, even though you can't rule out this type of failure I wouldn't be overly concerned. As noted above, this type of bearing can motor on for a long time after it has started to fail, typically providing a lot of warning. I had one going on a small trailer that I occasionally haul back and forth 80 miles between Portland and a cottage on the Oregon coast. It had been growling at me for well over a year, almost 2 years before I decided to do the repair. The only thing I did in between was to regularly check the hub to see how hot it was getting as my gauge for the progress of the failure. It's like anything else on our cars. I don't think if you are left by the side of the road, it will be from this bearing failing unless you've completely ignored all the warning signs for a long time.

Pictures of Failed Pinion Bearing - flash - 04-15-2013

yes, it can happen at any time. the amount of preload determines when. if it is a lot over the limit, it happens early. if it is only a little, it happens later. use also factors in. the more heat, the earlier. speed, track use, and the heavier the car (crap carried around, passengers, etc), the earlier it can happen.

the problem with running it with a failing bearing is the chances of particles getting in and screwing up other parts increases the more you go. if you catch it early, you may only need to replace the one bearing. if you drive on it, you may need to replace them all.

Pictures of Failed Pinion Bearing - mylz87 - 04-16-2013

Ok, still a rookie - Pre-load? Does anyone know what the failure percentage is? What does a typical repair run?

Thanks for the response guy's.

The search continues!

Mylz87

Pictures of Failed Pinion Bearing - ds968 - 04-16-2013

[quote name='mylz87' timestamp='1366119258' post='141419']Ok, still a rookie - Pre-load? Does anyone know what the failure percentage is? What does a typical repair run?

Thanks for the response guy's.

The search continues!

Mylz87[/quote]

No idea on percentage failure rate, no one knows that. Repair cost will be between 2,000 and 3,000 depending on the area, the shop, etc.

Pictures of Failed Pinion Bearing - flash - 04-16-2013

preload is the amount of pressure set on the bearing at installation. because this bearing was robot installed, and the case is cast, the tolerances accumulated in sometimes the wrong direction.

based on what i have been able to gather over the last 9 years, the failure rate is between 5 and 10%. that's pretty high for any such thing, but not the end of the world either.

repair is 8-14 hrs of labor, and anywhere from $130 to $1300 for bearings, both areas depending on how long you let it go, and what other damage occurs during that time.

it should not be a deciding factor in a purchase, unless it is already present.

Pictures of Failed Pinion Bearing - mylz87 - 04-16-2013

Thanks guys -

No, its not going to deter me from my search, it'll just join the queue of other things that play in my head at 3AM!