Mike J

[Cross posted to the 993 Forum]

This thread is about a recent project on my 97 993TT - clutch replacement and replacing the power assist clutch slave. Car has 95,000km (59,000) miles and no record of having the clutch replaced.

My clutch pedal has been riding very high since I bought the car over three years ago, and in anticipation, I bought a RS Turbo clutch kit from Kevin just after I bought the car - including a RS flywheel, GT3 disk and a modified motorsports pressure plate. While my engine is stock, it's always good to put in something that will last and take upgrades if they happen. That kit sat on my shelf for three years until I figured I should pull up my socks and put it in to enjoy that RS flywhee.

Rough list of new parts - Clutch

Clutch kit from Kevin (RS flywheel, PP, clutch disk, pilot bearing, RS throwout bearing, gear ring, flywheel and PP bolts, guide tube)
Clutch fork
Clutch needle bearings
Guide tube screws
Clutch fork shaft seals
Clutch fork shaft (not really needed except for the OCD people)
Rear main seal

I like things to keep things simple, so I thought I would replace the power assist slave (which was fairly new and working correctly so it just goes into storage) with a manual system, so I also bought:

- MPL Slave Cylinder
- Stock NA pedal cluster spring

Ok, I will skip a lot of the pedantic normal stuff getting to the clutch - except to mention that I do remove the transmission without dropping the engine or the torque tube ... that exercise remains with the student.

Here is the transmission removed and ready to be dropped by the transmission jack:



Ok, tranny out and clutch apart - and look what I find... PERFECT timing in that I maximized the use of the old clutch. The disk rivets were just touching the pressure plate, and the DMF had a bit of play.



Ok, flywheel off and I find the RMS is just starting to weep - I think this was original so that would be understandable...



So its time to build out the new clutch. The Turbo pressure plate requires a lot more pressure to flatten in able to put in the throwout bearing, so I built a press fixture to help - went a bit overboard!!



New clutch disk



New pressure plate and RS throwout



New RS flywheel and RMS - yes the gunk was cleaned off...



OK, next step is to put in the simpler non-power assist cylinder - and that involved capping the existing lines from the p/s pump. I could not find the proper caps in town to do this, BUT I did find some hydraulic hose ends that would fit -- see the one on the left.



So I cut the hose side off the fixture on my handy metal bandsaw ...



and then TIG welded the hole to make a new cap ---



ending up with ...



The pressure line cap is in place -



The return line is capped too - not so critical since there is no pressure there


There is the MPL Slave ready to go in. This has a volume increase of 30% over a NA slave, so its stroke is shorter but the effort is reduced. I elected to reuse the old slave clutch hose. Before hooking this up, I flushed the pentosin out with copious amounts of brake fluid to ensure a clean system.



and the MPL in place:



Next - upgrade the pedal cluster with a new spring... here is the old spring



Springs (the heavier one is the one going in - from the NA cars..)



Ok, so clutch in, transmission back in and installed, new slave cylinder, new spring in the pedal cluster, system bled, so start the car up AND

--- the car would not go into gear while the engine is running!

Ok that means the clutch is not releasing, but why? So I did some more work:

- I had a spare new clutch master, so I put that in just in case. I figured I had not used it for three years (with a bunch of different cars in the shop) so its not a bad use for it
- I removed the MPL cylinder and put in a new NA slave (that I had in stock)
- I bled the system with Super Blue, but then flushed it out with Castrol SRF, since it seems to offer a firmer pedal so it may give more stroke to the slave

Turbo master and naturally aspirated master side by side - they are identical - the one with tag is the new NA one BTW



AND THEN IT WORKED!

The clutch engagement point was very close to the floor, which is typical of this system, but a big change from the original clutch which, since it was very worn, had the engagement point almost at the top of the pedal.

SO I then changed out the slave with the MPL unit, and flushed again with SRF - and it WORKED. Definitely a lighter pedal.

Conclusions: - and its all subjective!!

- the stock power assisted clutch slave is the lightest, almost like a Civic clutch ..
- The pedal lightness with a stock NA slave cylinder and a Turbo RS clutch setup flushed with brake fluid is driveable but about 50% heavier than a corresponding RS clutch on a NA car, or about 2x the heaviness of the stock power assisted slave.
- the pedal lightness with the MPL slave cylinder and as above is about 20% heavier than a new stock RS clutch, and perhaps 1x heavier than the stock power assisted slave.

I know the 30% difference between the MPL and stock NA slave cylinder should result in a corresponding reduction of effort, but it feels more than that - and I am not arguing!

The MPL slave makes this solution very drivable - or at least from my small sample of bombing around the neighbourhood. My car is not insured for road use until spring, so that is when I will really be able to drive it more.

Pretty happy with the solution and am now waiting until spring - oh wait I have more mods to do!

Cheers,

Mike

Rick GT3

nice and thanks for the info.
this should be on DIY & sticky.

Johnny_law

Nice write up Mike.

I'm not crazy for the soft peddle. Hmmm.

Quadcammer

any tricks on removal or are you holding on to those secrets?

Mike J

It depends - you need a good transmission jack first of all - it can be done on your back with jackstands, but I am wayyyy too old for that.

I will write up the procedure in a bit ...

Cheers,

Mike

Knight

So with the MPL, the pedal effort equals say a 993 NA with an RS setup?

If so, I think this would be the ideal setup for me.

Never really enjoyed the light assisted clutch on these cars too.

Great write up Mike!

OverBoosted28

Mike, do you know how much HP the RS clutch setup is rated at? Probably gonna need a clutch pretty soon. Would like to know if it'll last with 520 HP. Thanks

TouringTeg

My AWD C4S trans was removed with engine in the car (on a hoist). Just a note that upon bringing the car home I noticed oil drops on the garage floor. Turns out the strain on the engine pulled the hose loose on the oil filler reservoir. Refit the hose, tightened the clamp, and cleaned up the oil.

Mike J

When we get together, I am sure you will try it. It's heavier than a newly installed NA RS clutch, like Rob's, since we compared them side by side last week. However, its lighter than say a NA RS clutch setup that has been in a number of years and is gummed up, like Jason's (which I will be fixing...).

I would love your opinion since I am now getting used to is, and losing my ability to compare. We need to have the cars side by side. Your current clutch will be 1/2 the effort of this one I think - but its still quite driveable (then again, I am a bigger guy..).

Cheers,

Mike

Mike J

I think so but you will need to ask Kevin for the exact numbers - but the clutch I have is not what he is selling now, the clutch disk has been changed by the manufacturer and sounds pretty strong. It will be similar to this one below:

https://rennlist.com/forums/996-turb...-445-00-a.html

Cheers,

Mike

Mike J

I have been receiving emails and PM’s about supplying some hints doing this job, so here are some musings -> I am assuming that the bulk of the work is obvious and you are competent enough to make it happen. If not, you might want to consider a professional, or hooking up with someone who has done this.

If you do not have a press, I would get Kevin to install the throw out bearing on the pressure plate before he ships, as well as press the pilot bearing into the flywheel. These pressure plates are really stiff, much stiffer than the NA ones, and my press was really challenged to activate the pressure plate, which you need to do in order to install the throw out bearing.

You will need to make sure the car is supported well, and the car is high as possible, because if you need to lower the nose of the transmission in order to clear the torque tube. Some things I did:

1 - drop the engine down on the engine mounts to the end of the threads if regular mounts, or if RS mounts, replace the bolts with longer ones to give at least 2" of slack. If you are going to incline the engine you will need to have some slack in the engine mounts.

2 - Once the motor is lowered on the mounts, you will need to put a jack under the centerline of the to support the engine in a triangle - the two motor mounts and the jack. That way you can control the tilt of the engine by raising/lowering the jack.

3- You will then need a transmission jack to support the transmission separately from the engine. Once you are removed all the appropriate h/w (like the driveshaft couplers, return oil line (just take it off the engine and cap it and the outlet on the block, hint: drain the oil out of the crankcase first), starter, shift rod, back up light switch wires, various covers and vents on the bell housing, you can start to work on the torque tube.

Remove the rubber cover, and undo the two allen bolts that hold the coupler in place and slide it back into to the torque tube. It should slide nicely, if not, you may have an alignment issue. In the center console between the seats, remove the storage bin/cassette holder to get access to where the handbrake adjustment is -> below that is an access panel. Remove the sound proofing, then the rubber plug, and you will see the two top bolts holding the torque tube onto the transmission. Remove those bolts, clearances is a bit tricky but it’s doable. Now go under the car and undo the front torque tube mount that holds the front diff and remove the torque tube mount - and then remove the lower two bolts holding the torque tube to the trans. Push the torque tube forward until the front diff is against the body, and with a cross strap you made that goes across the center tunnel and is held by a nut on the studs that normally hold the tunnel cover, shim up the torque tube against that strap so its as high and as forward as you can go. It should be solidly against the body of the car.

When you tilt the engine and transmission to the nose of the transmission lowers once the transmission mount is undone, the trick it to make the nose of the transmission clear the torque tube - once that is clear, you can undo the transmission from the engine and pull it off the engine since nothing it blocking horizontal movement (after removing the clutch fork shaft of course ... its in the manual). The clearances are tight but it does clear.

This is definitely doable with a lift, a good tripod stand to support the engine, and a good transmission stand to support the transmission. If you are working on the ground with jackstands, I would worry about getting the clearances so you can tilt the engine/transmission in a controlled way, and be able to pull the transmission off the engine in a very controlled and accurate way, since you do not want to bend the splined input shaft. I did not measure exactly how much clearance you need, at least 18" off the floor I suspect.

The re-insertion of the clutch fork shaft is a challenge on a lift, it will be a bear on your back. Same goes to install the rubber plug and retaining bolt/clip, if you drop anything it’s time to take it apart again (unless you stuff some shop rags into the space to catch things if they drop).

In a pinch, if you need more downward angle, you can remove the cross support that holds the toe control arms. Do not loosen the control arms themselves, that impacts your alignment, but if you mark the position, the four bolts will put the piece right back to where it was, and having it undone and hanging loose will gives extra clearance under the bell housing to be able to tilt the engine/transmission a bit more.

Personally, when I was younger, I tried to do a clutch job with a car on jackstands and with a regular floor jack on a 993 C2. I did get the transmission out and the clutch installed, but I could not re-couple the transmission with the engine if my life depended on it – the angles just did not work, and the alignment has to be pretty close for the splined input shaft to insert into the new clutch. I ended up spending hours trying to do it, and then once I gave up and decided to drop the engine, it took about 10 minutes to get the transmission coupled with the engine as well as installing the clutch fork shaft.

Lesson learned -> if you want to get fancy, get the right equipment including a lift.

Cheers,

Mike

chsu74

Very nice write up. Thanks Mike!

Texas993

Nice job Mike. That is exactly the setup I had in my Turbo R. Except that I did not have the NA pedal spring. I liked it a lot.

Overboosted - Kevin's kit easily handled my Turbo R power, which was about the 520hp that you asked about.

OverBoosted28

Thanks, I figured so but just wanted assurance.

Basal Skull

Mike - glad it worked out, nice write up!

Richard - I have a version of kevin's clutch in my car (not 100% it the same as this one) but seems fine with the 3.8, I know the original owner Don had problems with slippage with the Andial clutch and had Kevin's placed to remedy the situation.