Clutch Slipping and Heat

SmokinBBC

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Joined
Mar 25, 2008
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Location
Oak Ridge, NC
Been able to get out and drive for extended periods of time (1hour +). Ambiant temp around 90. Engine stays right around 195 to 200. Oil temp is around 215. No problems there. Trans tunnel is very hot.

Anyhow, if I floor it when it is this hot while moving and RPM's around 3500, I am getting clutch slippage. Starts out as normal and then you get slippage/grabbing. Didn't have a place to put it in fourth for a slow rolling start, but if I get a chance, I'll do that today just to make sure. I didn't smell any burning...but then again, I had the tops off.

The car is tuned rather well...when kicking it in at 3500 RPMS in 1st,2nd,3rd, you get thrown back in the seat. Peak torque of 560+ is around 3500RPMS.

I have no leaks, so grime on the disk is not likely. It's a Zoom clutch...about 3k miles in 3 months. Can it be the heat? It's seen some pretty spirited runs...perhaps a slight adjustment is in order?
 
Been able to get out and drive for extended periods of time (1hour +). Ambiant temp around 90. Engine stays right around 195 to 200. Oil temp is around 215. No problems there. Trans tunnel is very hot.

Anyhow, if I floor it when it is this hot while moving and RPM's around 3500, I am getting clutch slippage. Starts out as normal and then you get slippage/grabbing. Didn't have a place to put it in fourth for a slow rolling start, but if I get a chance, I'll do that today just to make sure. I didn't smell any burning...but then again, I had the tops off.

The car is tuned rather well...when kicking it in at 3500 RPMS in 1st,2nd,3rd, you get thrown back in the seat. Peak torque of 560+ is around 3500RPMS.

I have no leaks, so grime on the disk is not likely. It's a Zoom clutch...about 3k miles in 3 months. Can it be the heat? It's seen some pretty spirited runs...perhaps a slight adjustment is in order?

How much free pedal do you have?
 
That's good.
Pick one:
1)Not enough free pedal to insure full engagement
2)Glazed from slippage
3)Weak P/P springs (Overheating)
4)Clutch too small
5)Contamination on the driven plate
6)Worn out

There might be more, but I don't know what they would be.
 
I am going to go drive it hard to heat it up again...then do the slippage test.

Contamination...I'll get it in the air and pull the inspection cover next weekend for a look see...definely not fluid...it is dry at the bottom of the bellhousing and inspection cover.

I am thinking that some wear has caused the free play to reduce. I need to check the specs, but shouldn't the free play be at least 1 to 1/2 inch. Well I guess that depends on the aftermarket clutch set-up.

It's an 11inch clutch.

Glazing and weak springs are certainly a possibility. I can say the heat being generated is very high....perhaps slipping more than I realize...more friction...heat damage. I wonder if the trans is getting too hot...maybe not a high enough quality lube? I don't know what is in it.

Worn out...well, if it is, that would certainly suck. The stocker lasted 55-60 k before it wore out.
 
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Took it for a long ride.

First geat, kicked at about 3500....accelerated fast...clutch slipped once for a second, and grabbed again. Nows the time I wish I had a rev limiter.

Rolling sart at 10mph in 4th with a little gas...engine died...did it a couple of times with more gas..same result.

Drove it for another 45 minutes...good and hot. First 2 high rev rolling starts...no slipping...second 2...slipping and grabbing.
 
Thought about it a little bit. When I am driving at medium RPM's it is not taking much travel to disengage the clutch...so I probably don't have enough freeplay to keep it from slipping.

I'm going to reset the free play and see if I can get more than 1/2 inch out of it.
 
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