patricksd

First off, I did a search and found some great info. I was running the car hard last night, and noticed after doing it, I could smell something burning. I assumed this was the clutch. So, like any newbie owner, I jump on LS1tech and do a search!

From every post I read, it sounded like the clutch was going. Several people mentioned one way to test if it is slipping is do 35 mph in 6th gear and give it gas. If the rpm's shoot up, but the car doesn't go faster, its the clutch slipping.

Well, I did this, and the rpm's did not shoot up. Instead, they slowly climbed.

So, now I'm wondering, is the clutch really going, or was I granny shifting it too much? I don't pretend to be the world's fastest shifter, and last night I wasn't slamming the gears. Under normal driving, there are zero problems, no play in the clutch, it never sticks to the floor, etc.

The only problems I've noticed is the smell when romping on it (just last night) and sometimes it hesitates going into 1st and reverse (upon start up in the morning). Personally, I think the clutch is loose or a little worn (50,000 miles on the original). But I'm curios for your guys' expertise on the situation.

brad8266

iTrader: (23)

if the rpms didnt shoot up, the clutch likely is OK.

SladeX

While my clutch passed the 6th gear test, it didn't HOLD under WOT in 1st, 2nd and eventually 3rd gear.

The way I could describe it is a very faint surge where it'd grip and slip and grip and slip as you climb through the rpm range.

When I pulled the clutch, I finally saw that while I had plenty of material on the LS1 stock clutch, there were hot spots all over so I wasn't going crazy.

Now with the LS7 clutch, while there are times I think the clutch is slipping, a slipping clutch doesn't usually make the car go sideways while slipping. Some friends at the track verified for me that I was breaking traction instead of my clutch going.

patricksd

Mine holds, so I'm not sure what the problem is. Maybe I was riding it too much last night, I don't know.

To be honest, I've never had a slipping clutch - what does it feel like? A surge in the rpm's with no acceleration? Kinda choppy on takeoff?

I'll probably switch to the LS7 clutch in the next few months, but I'd like to wait a bit before dropping the $$$.

SladeX

My clutch kinda gave me motion sickness at WOT. Ever been in a car with someone who couldn't keep their speed consistent? It's kinda like that feeling. At it's worst I finally was able to see it on the tach vs speedo. Although the RPM was climbing ok, the speedo was spiking up in stages.

When I first started noticing it, it was 1st gear only, 2nd gear started doing it, but it was still hard to catch. Once 3rd gear was doing it too, the surging was obvious in 1st and 2nd. The problem is 1st and 2nd climb too quick to do a good long hard stare at it and still keep the car relatively straight.

patricksd

That does make sense. Come to think of it, if I am cruising in 2nd say between 2000-2500 rpm's, I will sometimes feel a surge.

Is that the slipping you are describing?

Ranger

It very important to separate rpm "surge" that

(1) may come from shift synchronization issues or power shifting.
(2) may come from slippage of the clutch under full power after the clutch grabs fully post-shift.

Some of the descriptions in this thread have unclear circumstances, insufficient to conclude the clutch is in fact slipping.

Ranger

SladeX

The slipping I am describing would occur once the clutch is "fully released". Basically off an idle launch then going WOT, once into the powerband (2500+), the surging would occur. It is not an engine surge as someone might suspect as it only occurred in the lower gears, once in 4th and up, the surge was non existent.

Like I said, I changed the clutch out, saw heat marks and have not had it come back. Latest dyno shows no engine surging whatsoever, just a nice clean torque curve so I wasn't going nuts, it really was the clutch slipping when full throttle was applied. As I stated earlier a 6th gear 35mph WOT attempt would not slip. I even tried a 5th gear version to see it held fine. It was only until the same symptom appeared in 3rd that finally convinced me to change the clutch.

I did my clutch change in October 06. I dynoed the car shortly after that. No engine surge, just healthy LS1 stock motor. I also had the transmission rebuilt in April 07, the rebuilder showed me BABIED internals with only natural 8 year daily driven wear. All my complaints were hydraulic (and fixed at the time of the clutch change).

patricksd

I think what you meant to say is that my descriptions are unclear (which I take full responsibility for, since in fact, I've never had clutch issue with a vehicle) - for the circumstances I outlined are very black and white:

#1 After WOT runs, there is a burning smell.
#2 There are instances where getting into 1st gear and reverse can be difficult (not a two handed thrust, but putting it in neutral and pressing the clutch in again)

I'm just going to replace it and call it good.

Ranger

#1 If this includes strong shifts that aren't precisely timed, you can induce the slip that causes Eau de Clutch.
#2 What does your clutch fluid look like?

Ranger

patricksd

#1 You may be right about the "incorrectly" timed shift. I'm still learning this bad boy!
#2 I had the clutch fluid changed less than 300 miles ago.

By the way, it should be mandatory reading for anybody with an M6 (or any manual for that matter) to read your site. VERY informative.

Ranger

Thanks, patricksd.

I see a lot of members swapping clutches unnecessarily, based on
(1) faulty diagnosis of slippage
(2) pedal issues that are curable
(3) vendor advice accepted uncritically

On the other hand, a clutch that is actually slipping under load is a safety hazard. But alway want to be sure it really is slipping.

Ranger

patricksd

You are welcome! I firmly believe your website link should be a made a "sticky" in this forum. It would go a long way to answer the questions that pop up daily for new drivers. Plus, the fact you ran 10.85 with a completely stock (albeit LS7-powered )Corvette, was all the proof I needed you knew what you were talking about!

After discussing this with you, I think I just rode the clutch too much during the shift. I really slammed the gears in this thing once, and never smelt anything. But what happened the other day, was a slower, more direct "clutch in/clutch out" movement. That probably lead to the issue I described.

I do plan - however- in the future of changing the stock clutch and hydraulics. More for peace of mind than anything. At this time, I'm leaning towards the LS7 clutch and LS2 flywheel combo.