Sql

Want to share this with you guys as there may be someone in a situation similar to mine with the noise that seems to be hard to diagnose and there is no info about it to be found, at least I could not find anything to help me out. Every forum keeps saying how 996tt gearboxes are bulletproof etc, well it looks like they are not THAT bulletproof.

Anyway, the problem with my car (2002, manual 996tt) was the noise that seemed to be coming from the gearbox starting at 3rd gear, all the way through 4th, 5th and 6th. It could also be heard in 2nd gear but noticeably quiter. It produced a sound similar to a bad bearing noise/whine/whirl and it appeared ONLY when i accelerated. Noise was not there when coasting or decelerating in gear. When i pressed the gas pedal it produced the noise again, immediately.

Here is my try to capture the noise on the video:


You can hear it best at around 0:26-0:28 s mark.


Took the car to 4 places, including nearest Porsche Service / Dealership. Noone could tell me what could that be.

Had my gearbox oil changed and found this:





That got me seriously worried but then I realised maybe at the first fluid change after around 55k miles it was not that abnormal.

The thing is - after another 500 kilometers the plug looked like this:



5 HUNDRED kilometers.

Something was wrong for sure.

I then figured I could try to email a US-based company called G Box, that specialises in rebuilding Porsche gearboxes.

Got an answer within 30 minutes.

"This is a classic pinion bearing, thrust bearing problem. The part number is
999-052-164-00"

Finally had at least an idea of what could be wrong!

Found it on a Porsche diagram (part number 25):



Took it to my friend's shop to get it done properly.

So next day the gearbox was out.



And we could proceed with the surgery:



And take it apart, part by part:







Another "floor":





And then we were there, at the very bottom where the problem was located:



Right behind that brass bearing there is another one that is the part making that whole noise:



*** part number 574710/1, Porsche part number 999.052.164.00

You can see the wear in pic below:



Due to the fact the brass cage bearing is located so close to the faulty one pictured above and looks like it could get a bit worn because of the pieces coming off the other bearing, I decided to replace that one as well:



SKF part number N 308 ECM, Porsche part number 999.110.119.01

Car is on the road again!

Absolutely no noises, flawless work!

Hope this thread may help someone facing the same issue in the future!

RxPorsche

WOW thanks for sharing

Hoosier_Daddy

I wish I had a friend like you have!

jpflip

This is very interesting. Thanks for taking the time to post those pictures. Any special tools needed to reach this bearing ?

nick49

Thanks for the write up! Nice pics too.

I can't help but to think the bearing races were improperly hardened. That does not look like normal bearing wear. I assume there is another race below the pic of the worn one, does it look the same?

May have a good look at second gear, dogs and syncros. The 2nd pop out issue is probably the most common Turbo trans issue.

Kevinmacd

Looks like pitting to me more than wear! Pitting is usually due to contaminants in the oil.

tvurt

I had mine replaced a few years ago with my syncros and third gear. Looked EXACTLY the same. 40,000 miles factory gear fill.

Tom

Macster

Since the transmission is not nearly as at risk to the introduction of acidic compounds, unlike for example the engine and its oil supply which receives constant exposure to acidic compounds produced from combustion, that is not pitting, but spalling.

Spalling can occur under various conditions (corrosion is one) but in this case I think it arose because the bearing was unable to tolerate the normal service pressures/forces.

The bearing's metallurgy was sub-par. In short the bearing was bad and it failed...unless the bearing had whole lots of miles or was subjected to extreme usage (tracking) or the wrong lubricate used.

Sincerely,

Macster.

SSST

That's exactly what I was thinking. There must have been a bad batch. It happens.

mdkelly1

Good information and good photos! Really appreciate the effort you made to post this.

GTgears

Those of us in the gearbox business see that bearing go bad all the time. That same bearing is in all Cup Cars and GT3s in addition to the Turbos. for the street cars it tends to wear out faster on the turbos, and you hear about it more often on them than GT3s, probably because of the difference in power levels. But it is a known weak point of the gearbox, and thus why the guy at Gbox called it the "typical thrust bearing" failure.

One thing that I think will help more people avoid or prolong this issue and the need to rebuild their gearbox is to pitch Porsche's gear oil service intervals in the bin. 55K is just way too long to run gear oil on a high performance vehicle that is driven even half as hard as Porsche intended. For gently driven street cars I tell people to change their oil every 30k mi. If you drive it hard, change it every 15k, and if you track it, count every weekend at the track as 2500 mi. towards that 15k number. half a dozen track days and you better be changing your gear oil regardless of mileage in between.

That's a $225 bearing and if you don't have a friend, the labor to get to it and replace it is $2000-3000. You can do a lot of oil changes for that much money. It's cheap insurance. I can't guarantee that it will prevent you from facing the same issue at some point, but I am confident that it will put off the failure longer and get you more miles between services on the box.

ca993twin

Is this the same advice as you'd give for 993 Turbo transaxles? Are the internals similar?

puma

Damn you have a low post count but those posts are awesome

Thanks GTgears for sharing your knowledge even if people are not your customers, that's what brings customer to your place, availability and honestly, just like Kevin does on this website.

Sql

True. Even an unauthorised Porsche service here quoted me $1000 to just get the transmission out in order to start looking for what's wrong!

My friend charged me that for getting the trans out, taking it apart part by part, putting it back together and getting it back on the car!

I only had to buy these two bearings on my own.

nick49

Thanks for the info, GTgears. What gear lube do you recommend for the turbo 6 speed? I've got about 20k miles on mine, I think I'll dump it and freshen it up.