FlattestSix

Hey all, I picked up my '99 996 about 2 months ago with 71k miles on her. She's been running great so far with no issues (original IMS). When I took her to my indy for the first oil change, he was really pushing me to get the Clutch + IMS swap done given the mileage.

I had an oil analysis done by Blackstone and it came back perfect. No high levels of metals or additives found. The clutch feels solid when driving and the PPI at the time of purchase came back with no issues.

So my question is, do you guys feel like I should follow the Indy's advice despite these facts and just get the Clutch + IMS done for peace of mind? Or, save my money for the time being.

ZuffenZeus

Yes, ... replace the following...

1. Clutch kit (sachs)
2. Dual Mass Flywheel (LuK)
3. IMS - IMS Solution from LN or at least the dual row Retrofit.
4. RMS
5. AOS
6. CPS - crank position sensor

That's a short list.

Marv

It's kind of a ticking time bomb. There is no assurance it will or won't happen, but if you have the resources now, then getting it done will only give you peace of mind.

Also, it gives the mechanic a chance to see if there is anything else that might be needing attention.

996-CAB

ZuffenZues is right, but I will add that you or your tech need to get the IMS bearing from LN Engineering and follow all the instructions to register the new bearing. It is easy to do, but it requires you or your tech to return the old bearing, so make sure one of you takes care of it.

hbdunn

All very high on my list of things people replace that are working perfectly fine.

hatchetf15

OP - If you’re happy with how the car was serviced the previous 71,000 miles, drive it and monitor. The IMS bearing just won’t explode 99.99% of the time. You’ll see signs and symptoms for injectors, IMSB, pads, etc; through UOA, ECU data and filter inspections. If you monitor your cam deviations, AOS vacuum and UOA (every 3,000 should give you cheap enough peace of mind) and the clutch is fine, wait.

I had my tech bust open the motor to replace the IMSB with an LN and found an updated non-replaceable bearing already there. We both failed to catch that fact in the rebuild and service records. So wasted money due to unfounded worry. If this was an M96/03, I might elect to break in there at 71,000. With an M96/01, probably not without any empirical evidence.

My personal experiences with the evil that is the M96 AOS say, if you do anything preemptively, install a UAOS.

Porschetech3

I would either take an oil sample from the dipstick every 2 months religiously and send to a Lab for testing,( looking mainly at iron levels), and if any red flags go immediately to plan B, ( it would be like a cheap engine insurance policy for only a couple hundred $$ a year) or go ahead and put in the IMS Solution if your finances allow, plus the other while your in there's.

I bought a 99 Cab 6 speed for my oldest son to play with about 6 years ago, and 2nd gear had been slammed a few too many times, so I pulled the trans to install new 1st and 2nd syncro's, and of course a new clutch/pp/TO bearing, and while I was there I pulled the IMS to replace it ( 70K miles) and low and behold it had started to fail !! It was just in the first stage of failure, but the thing about the 99 dual row bearings is that they will continue to shed metal for many many hundreds/thousands of miles before they start flopping...(catastrophically)..The weaker single row IMSB will fail much much quicker, so quick that it would be hard to catch..

wthensler

I had everything done in my ‘99 C2 at 64,000 miles, mostly out of fear. Turns out everything was perfect, it didn’t need any of it done.

Through various sources I’ve since heard the IMS wasn’t an issue in the ‘99s, but whatever fix Porsche tried actually made the problem worse.

I’m not going to steer you one way or another, just providing one data point. Oh, and like you my oil analysis was great (pointing away from an IMS problem).

I regret selling it (original owner, it was in perfect health ) and pretty much gave it away due to the dump it had taken via the internet, but didn’t have garage space at the time.

Porschetech3

Porsche didn't try to "fix" the IMSB problem after the 99 models, what they were doing was to make the engine "lighter" by using the single row IMSB, the IMSB problem had not blown up like it did with the single row IMSB in the 2001 up to 2006 models. But the dual row is not totally immune to the disease either...

sdematt

Welp, my experience was I did the clutch, shop said IMS looked fine and didn't need doing.

6 weeks later, metal in the oil.

So, would recommend if you're doing it anyway, just get in there and do it.

Pay once, cry once. Listen to your gut. Happy with my 3.8, but would have probably pushed it several years to the right if I had had the opportunity.

ZuffenZeus

I know that feeling of regret. I had a nice 2002 coupe that I sold with super low miles. I put a lot of sweat and blood into that car.

The '99 had the dual row bearing which could handle more load than the successor - the single row 6204 bearing. The 6204 bearing was a nightmare and prompted the class action lawsuit. As Skip mentioned, the dual row can fail, but it's a slower death than the single row 6204. That being said, if I were have the transmission removed, then it's a no brainer for me. I'd put the oil-fed IMS Solution in the engine. Remember, the other side of the intermediate shaft has an oil fed plain bearing like the IMS Solution and it doesn't have a problem. The AOS and RMS are cheap parts but can be costly to install later. Do it now and save the hassle.


Here's a picture of when an owner that lives near me didn't listen.

philbert996

I was in the same situation 3 1/2 years ago when I bought my ‘99.
Do I throw a bunch of new parts on a car that’s running perfect?
My answer was yes.

I won’t list everything that was done but I’ll say what I think were the 3 most important items to do.
IMS Solution
AOS
NEW Genuine Porsche Fuel Injectors

ZuffenZeus

Yea, I never understand people that say that won't handle something proactively because it's "running perfectly". I just changed out the transmission fluid on a '99 C4. The car has 90K miles. The color of the fluid was dark like molasses. Looked like old engine oil that hadn't been changed in years. What you wanna bet it's the factory original fill?

It's still crazy that a lot of ol' school mechanics preach that transmission fluid is a "life time fluid". I've heard that many times in my life.

Carlo D

I just dyi’ed my IMSB, rms, oil
cooler, oil pressure sender, coolant reservoir, a tensioner, flywheel, clutch and plate after my clutch completely stopped engaging. I took out the old LN retrofit and it looked perfect however why would I want to go through this again in the near future. The retrofit was however overdue from recommended change interval. I did choose to do the RND roller bearing as I didn’t want to pay for a Solution. Now I just gotta put the transmission back on 😅

rcipriani

I have a 1999 986. 84,000 miles. Replaced IMS. It’s a 2 part bearing and it looked brand new. However if you need a clutch, I would replace it. I understand the the percentage of failures in the 1999 is infinitely small.