slipping clutch question

[titaniumdave]

I was at the track a week ago and in the last session of the day, my clutch started slipping in fourth gear. Everything was going great before that, it holds in all the lower gears but once I hit v-tech in forth gear the RPM's rise like crazy. I have a powergrip clutch which had 70% friction material left 4K miles ago when I had the engine out. The clutch does not seem to fully dis-engage now too, hard to shift into reverse and it can be hard to shift into third somtimes.

My wife was doing her first novice track day as well, and I rode with her the last session. She was slipping the clutch more than I think one should, I wonder if she has glazed the friction material and now it does not want to grip. This could account for the slipping in fourth, it does not fit with the difficulty shifting. I do not see any leaking from the slave cylinder and the clutch resevoir is still full, so I don't think that is the problem.

Any ideas?

 

[Larry Bastanza]

Sorry to say Dave, but it really does not sound good for the clutch. You can check the end play, if tight it could cause it to slip. You can also check for fluid leaks, but the pedal would be soft, and I am sure you would not ask about that.

HTH,
LarryB

 

[titaniumdave]

I am still trying to get more information. Driving it today I noticed the pedal seems to go all the way to the floor but not fully release. I will check the slave cylinder and linkage to make sure nothing odd is going on there, and free play at the pedal to see if that is still in spec.

Seems odd to go through 70 % of the friction material in 5K miles, it had 25K on the first 30 %. Will the clutch lose grip before it is worn out?

 

[Larry Bastanza]

I do not think the clutch would loose grip, however you also mention not full disengagement, which sounds like a spring tang in one of the disk hubs may have broken (I see this a lot on rebuilt OEM clutches), so maybe this is also keeping the clutch from full pressure too.

Lets hope I am mistaken.

Good Luck,
LarryB

 

[titaniumdave]

Like a crack in one of the 'fingers' of the spring where the throw out bearing is captured? Any way to inspect other than looking at it once it is out? I do have an older Comptech powergrip clutch, for what ever that is worth .

 

[Larry Bastanza]

Not exactly. I was refering to the spring loaded hub in the center of the disk. They have small tangs that hold them in, and tend to break, expecially if the hub has been remanufactered. I see that the Comptech PGII disks due have springs also, but I was under the impression these are NEW, not remanufactered.

HTH,
LarryB

 

[titaniumdave]

I thought those springs were there to take up shock from engagement?

I will crawl under the car tomorrow and see what I can tell before I drop the tranny .

 

[Larry Bastanza]

Yes, that is true, but the tangs that hold then in on OEM clutchs do break. You can remove the inspection plate, but you can only see the back of the fylwheel, not much to look at, unfortunately.

Later,
LarryB

 

[Gerard van Santen]

I do not think the clutch would loose grip, however you also mention not full disengagement, which sounds like a spring tang in one of the disk hubs may have broken (I see this a lot on rebuilt OEM clutches), so maybe this is also keeping the clutch from full pressure too.

Lets hope I am mistaken.

Good Luck,
LarryB

Last year I had the same symptons with OEM frictions plates. And as Larry mentioned one of spring tangs was broken, so a damper spring came loose. When I opened the clutch, the outside (tranny side) friction plate had about 90% of friction material and the one the flywheel side (the one with the damper spring that came loose), had about 40% of friction material.

Gerard

 

[titaniumdave]

Well, thanks for all the help with this one. I just replaced the clutch last night and Larry and Gerard were right about the problem. One of the spring tangs had broken off, the other 2 were loose and about every part of the clutch was damaged. I am not sure what the order was as far what broke first, but I think it is clear I won't get a core refund on this one!

Some shots of the damage...

I replaced the clutch with an Exedy single disk, 6 puck clutch. My first impressions are very positive, much more streetable than the PGII I just took out. The pedal feel is soooo light, I think I will get used to it pretty fast. I have a track day on Monday and will report back on how the clutch works under high load.

 

[apapada]

thank you for sharing the information. May I ask how long did it take you to do the job and what procedure did you follow ?

tia

 

[titaniumdave]

thank you for sharing the information. May I ask how long did it take you to do the job and what procedure did you follow ?

tia

I was able to get some very good help and a lift. The 2 of us took 4 hours from when I pulled the car into the shop to when I was driving home. I am amazed how much faster things go with 2 sets of hands! Oh ya, and help from Morgan, the most experienced NSX tech in the Northwest .

We tag teamed the the work, I dropped the wheels and unbolted the reinforcement off the bottom of the motor cradle. The e-brake brackets, wheels sensor brackets were removed but the lines were still connected to the calipers and hubs. I marked the camber settings with paint and removed the lower a-arm bolts, toe links' bolts and sway bar with the links attached.

Meanwhile, Morgan removed the shift linkage and clutch slave cylinder and started loosening mount bolts. We popped out the axles, I removed the intermedate shaft and carrier while Morgan drained the tranny.

At this point Morgan went the top of the car, removed the air box, wire harness, starter, tranny end mount and 2 housing bolts. I am not sure exactly how all this worked, I was prepping the clutch pressure plate by installing the new throw out bearing with a press and cleaning the flywheel for the bearing.

We went back to the bottom of the car, removed the rest of the housing bolts, engine mounts and the little cover on the bottom of the clutch housing. We had a stand under the oil pan/header for support and a transmission jack under the tranny at this point. The tranny came off pretty easy and the 2 of us dropped the it out, with me making sure nothing snagged on the way down. We strapped the tranny down and left it, next removed what was left of the old clutch, impact wrenched off the flywheel. I pressed out the bearing from the flywheel, pressed it into the new flywheel while Morgan cleaned up the cluch housing and made sure the parts which had come off the pressure plate had done no significant damage.

We bolted the flywheel in place, torqued and locktited. Installed the alignment tool, slid the disk on and bolted, torque, locktited the pressure plate onto the flywheel. We jacked the tranny back up into the car and it slid in place on the first try! From there it was the process of putting it all back together. Little cover, housing bolts, engine mounts, suspension, sway bar, cables, lines, reinforcement, wheels. then to the top.

Morgan was the one who did the tedious stuff on the top of the tranny, putting the starter back in, wires brackets and harness and air box. Lots of stuff in a very small area.

Hope this helps, if you have a specific question that I did not touch on let me know.