996 Turbo / GT2 Turbo discussion on previous model 2000-2005 Porsche 911 Twin Turbo and 911 GT2.

High RPM shifting issues while racing

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Old Sep 26, 2010 | 03:05 PM
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High RPM shifting issues while racing

There is an issue I'm noticing in my car, that I wanted to hear some input on.

The car is a stock '03 996TT X50 with 26K miles. It has a working accumulator and stock slave (as far as I can tell), but it does have an issue where it leaks a TINY amount of fluid out of the power steering weep valve at the top. I'm not even talking drops, but just a bit of fluid sweating out after hard runs, as I can see the residue on the green tag. Not sure at all why it's doing this..but I suspect its related to the problem described below due to the relationship of the clutch/PS hydraulic systems.

When trying to shift quickly (doesn't matter what gear.. 1-2, 2-3,3-4) at red line, I have to wait a bit before it will slide into the next gear. This totally kills the acceleration as the turbo spins down and back up again. Conversely, if I shift at 6000RPM or under, I can "speed shift" the car like I can in all other cars I have owned.

At first I thought maybe the clutch was not disengaging all the way, hence the high RPM shifting issues. So I did the test: ebrake on, put the car in first gear, depress the clutch and bring the revs up all the way to the revlimiter and see if the car moves -- it didn't move at all. In other cars where I had a clutch that did not disengage fully and caused high RPM shifting issues, the car would "creep" forward under this test.

The next thing I tried was a variation of this... ebrake on, clutch in, hold RPMs at redline and row through the gears. This is where it gets interesting. Most of the time it slides into gear perfect. However, if I hold the RPMs at redline, quickly depress the clutch and try to slide into a gears...it has a "block" and then after a couple of seconds it will slide into gear. I'm thinking this has to due with the complex hydraulic assist system of the car not disengaging the clutch quickly enough under that condition. But I'm curious what could be causing it... accumulator or slave going bad internally?

I've always planned to do the GT2 slave conversion, but I wanted to hear if I'm on the right track here. Could my slave be going bad and hence bypassing some of the pressure on quick clutch in?

I have no *visible* fluid migration, although I haven't tried to measure it precisely.

Thanks for any input.
 

Last edited by racegate; Sep 26, 2010 at 03:07 PM.
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