Lysoleverywhere

2003 996 Turbo
6 Speed

1st - 4th gear seem okay, but if I'm cruising in 5th or 6th gear and I floor it...the rpms shoot up from 2500-4000 and the car doesn't go anywhere. I've never heard of a clutch slip in only 2 gears. Any idea what this is?

Macster

Clutch can slip whenever conditions right. One test -- which I do not ever recommend anyone perform -- is with transmission in 4th gear to drop clutch and floor accelerator. If engine dies clutch ok. If not then clutch is obviously slipping and due for a replacement. But I repeat never perform this test. It was passed on to me by an old school, circa caveman era, mechanic.

Anytime you get a disconnect between engine speed and vehicle speed in a manual it is either clutch slippage or tire slippage.

Unless you tell me you are driving on very slick pavement I'm going to guess the car's clutch is slipping.

If find it hard to believe if pavement not slippery/slick the car could with its 4 wheel drive system break all 4 tires loose at 2500 rpms in 5th or 6th and keep them broken loose for long enough for revs to rise like you report. That's some impressive power output.

Besides if the tires were slipping shouldn't you see the traction/PSM light in the dash come on? My Turbo's tires broke loose once under hard 1st gear acceleration and a light off to left side of the dash flashed on momentarily. I didn't bother to get out the manual and see what it could have been. I'll do that after I post. I need to be more familiar with the manual and the car anyway.

Sincerely,

Macster.

Dock

Is your engine stock?

Lysoleverywhere

Have Ultimate Motorwerks ECU tune. That's about it.

Dock

I don't think there is any chance that the tires are breaking loose with the RPM at 2500 in 5th or 6th gear.

So you have no issue with clutch slippage when going WOT in 2nd gear starting at 2500 RPM?

Lysoleverywhere

Non whatsoever. 1st-4th is strong as a mule. 5th-6th WOT sounds like a C4 Transmission with a big stall.

Macster

Transmission torque multiplication in lower gears lessens stress/load on clutch so unless clutch really really bad it can hold real well in the lower gears.

In 5th and 6th (and even 4th) gear torque multiplication diminished and clutch under more load especially if engine in the sweet part of its torque band and then with the pedal floored. If the clutch has any weakness at all slippage almost guaranteed.

Clutch. (Or possibly the clutch actuation hardware somehow faulty and this results in some pressure being applied to the clutch under hard acceleratio in the higher gears which causes the clutch to become partially disengaged and thus slip. Still, almost certain the tranny will have to come out in order to determine the exact cause and perform the necessary repairs. A qualified technician's opinion should be sought out before ok'ing such work.)

Avoid slipping the clutch any in the higher gears to avoid overheating the flywheel to the point it may not be reusable.

Sincerely,

Macster.

Kevin

It looks like your clutch has failed.

The pressure plate is not up to the task with 500ft lbs of torque.

Run up thru the gears, 1st, 2nd and 3rd then quickly shift to 5th..

The RPM will bog or race to redline.. This is a classic test to "check the condition of your clutch" If it races to redline then your clutch is toast.

You are making some good power, I have a clutch on the shelf. The decision right now is> do you keep your dual mass flywheel or upgrade to a lightweight flywheel.

You have to be carefull about burning your dual mass flywheel, if you get it hot and burn the surface you will need to purchase a new one $968.00 worth..

Dock

I highly recommend Kevin's LWFW.

If you want to test drive one, let me know...I'm in West Cobb and have Kevin's clutch/LWFW package.

Macster

Earlier today -- in my 03 Turbo 6-speed manual -- came upon a long empty -- uphill too -- stretch of highway. At 2500 in 5th gear floored the pedal. Engine rpms gained speed in time with vehicle. Had the boost display on and saw 0.8 bar boost.

Kept my foot down well long enough that if the clutch was going to slip it would have. Tires didn't break loose either.

Tried the same thing again going up hill in 4th gear. Same results save I only saw 0.7 bar boost. (My info is the engine is set up to produce just 0.7 bar (max boost and of course stock) but that sometimes a reading of 0.8 bar is possible though an artifact of the boost gage or something.)

Not sure what margin these clutches have. If you have a mod'd car and I think I read you do -- chip mod at least -- it could be the engine's putting out more power enough more power, or in a peaky way, that overwhelms the clutch and it slips.

One can't know the condition of the clutch either. It might be on its way out and the extra power is just the final straw.

One thing that occured to me while I was testing: That your clutch doesn't slip in the lower gears could be the chip limiting power/torque output in the lower gears to avoid undo drivetrain stress. I know of, second hand, at least one automaker who does this with its manual equipped cars (BMW and its 5 series fitted with the V10 engine) to apparently lessen the wear and tear on the car's drivetrain that dumping all 500hp and 383ftlbs of torque which is kind of low ain't it, considering our Turbos kick out 413ftlbs, this mighty (ahem) V10 can put out.

Sincerely,

Maccster.

Kevin

Macster there just isn't enough load in the early gears. There is a direct relation between time and load. The gear ratio's and road resistance that has a effect on the clamp force/pressure plate and clutch disk.

Lysoleverywhere

I'm in Alpharetta. I'd definitely be up for a meet to see how it feels. When are you available?

Macster

Ok. It was just a theory. I do remember from a gasoline test the testers found little difference in the various gasolines in the BMW 5 with the V10 and surmised the engine controller was limiting torque to avoid putting undo strain on the engine or drivetrain and the new PDK transmission was suggested to be the drivetrain component/assembly most likely.

I did mention in an earlier post that one possibility was the torque multiplication in the lower gears did reduce the load the clutch had to deal with and lack of slippage in the lower gears was a result of this.

Sincerely,

Macster.

medtech

The other thing Joe forgot to mention is that his clutch could easily have over 70k miles on it right now. Unknown if it was ever worked on before.

Lysoleverywhere

A little update:

I can't get the clutch to slip now. Today was a much warmer day. 72 degrees vs. 50 when it was slipping. Took it to my indy and we couldn't reproduce the 5th, 6th gear issue that I had the other day.

medtech is right. It is in fact still on the factory clutch with 70,000 miles on it. Never replaced. When I first got the car, I couldn't get it to slip if I tried when it was stock. Kevin's ECU flash combined with a little cold weather may have been too much for the old stock clutch to handle. We also found a transmission mount needed to be replaced. Fixing it tomorrow and will update.