Clutch?

[TerryLiv]

Yesterday while accelerating in 1st gear the car lost some power without any odd noises. At the next light it was obvious that something was slipping, even off boost. Felt like the clutch. Today I put it on 4 jack stands and all 4 axles worked, so I am assuming it is the clutch. The clutch is 8 months old with about 1500 miles and hasn't been slipped much.

I did notice the right front outer axle boot was loose and leaking new grease.

Suggestions about other things to check before I pull the tranny?

Thanks,

Terry

[Cloud]

It would slip in higher gears before it slips in lower ones, so get on the highway in 5th and get it into the powerband, it's pretty easy to tell it's failing at that point, it will rev unnecessarily freely if it isn't holding, much like tire spin.

[DemonStreetMachine]

Does it feel like it is slipping all the time? Is it a stock center diff is in the tranny?

[TerryLiv]

Does it feel like it is slipping all the time? Is it a stock center diff is in the tranny?

Yes, it feels like it is slipping all the time. Newly modified 4 spider CD from TRE. Clutch pack LSD in rear. Cheap spring type of LSD in front.

I have never broken a CD before. Is this the symptom? No noise when what every is was broke, just loss of power and easy revving.

Terry

[TerryLiv]

It would slip in higher gears before it slips in lower ones, so get on the highway in 5th and get it into the powerband, it's pretty easy to tell it's failing at that point, it will rev unnecessarily freely if it isn't holding, much like tire spin.

Brian,

I know the feeling of clutch slipping. This seems to slip all the time. I know if it slips in first off boost that it will slip at higher gears so have not felt the need to make it worse if it is a clutch disc.

9 years ago I was testing for a noise in the drive shaft, and removed the drive shaft to see if the noise was gone when I decelerated. The car was then powered by the viscous coupling and the CD. This gives that feeling.

Terry

[Cloud]

So you are saying you are positive it's the clutch then? Initial post indicated you wanted additional signs for diagnosis. If it is worse in the upper gears, it's the clutch.

What clutch are you using, and what power level are you currently at? I seem to recall you running a pretty potent setup, so anything less than the holding power of 2900 and street disk or a 2600 with puck probably isn't going to cut it.

[Dane Becher]

Terry,
Have you checked to make sure your clutch hydraulics are releasing fully, giving "free pedal" (i.e. not riding the clutch)?

IIRC your DSM is a 1Ga, right? Is it a 3 bolt rear? I know you said all 4 wheels spin when on stands, but is it still possible a rear axel is broken?

I guess if it's not in the rear end or clutch hydraulics, the only other logical thing to do is pull the tranny to inspect the clutch and CD. Does the 4 spider CD require a viscous coupling (I've never worked with a 4 spider)? If so, the VC might be another thing to consider.

[TerryLiv]

Terry,
Have you checked to make sure your clutch hydraulics are releasing fully, giving "free pedal" (i.e. not riding the clutch)?

IIRC your DSM is a 1Ga, right? Is it a 3 bolt rear? I know you said all 4 wheels spin when on stands, but is it still possible a rear axel is broken?

I guess if it's not in the rear end or clutch hydraulics, the only other logical thing to do is pull the tranny to inspect the clutch and CD. Does the 4 spider CD require a viscous coupling (I've never worked with a 4 spider)? If so, the VC might be another thing to consider.

Dane,

The clutch pedal feels normal. Normal pressure to release it and Some free travel and a normal release when letting it out for engagement. Except there is no immediate grab as before. It just gradually slips as the car begins moving.

It is a 4 bolt and when on 4 jack stands in neutral, moving any wheel would move all the others, which was my way of determining that no axles were broken. Is it possible to have a broken axle and be able to turn other wheels when rotating the one with the broken axle?

Yes the 4 spyder still requires a viscous coupler. The 4 spyder works the same as a 2 spyder, but has 1/2 the force applied to each set of spyder gears. I have been under the opinion, Maybe justified, maybe not, that viscous couplings don't just break, but the fluid becomes gradually degraded until there is very little viscosity left. Is this correct?

Thanks,

Terry

[TerryLiv]

So you are saying you are positive it's the clutch then? Initial post indicated you wanted additional signs for diagnosis. If it is worse in the upper gears, it's the clutch.

What clutch are you using, and what power level are you currently at? I seem to recall you running a pretty potent setup, so anything less than the holding power of 2900 and street disk or a 2600 with puck probably isn't going to cut it.

Brian,

I don't know what power level I am at, but could be in the 600 whp range. I haven't tried upper gears with power yet. So I am not positive it is the clutch. Clutch is the most significant single disk clutch sold by South Bend Clutch. It is their DXD-F-S, sprung hub 6 puck.

If it is the clutch, it all of a sudden decided to slip. It didn't gradually get to that point. Something broke.

Thanks,

Terry

[Overkill]

Didn't you just raise your boost level substantially by reconfiguring your wastegate hose routing? That extra boost may have put your clutch in its place, but its hard to say since it was sudden.

[Cloud]

I have had a VC fail, when I opened it to assess the situation the fluid inside was thin, and had burnt sludge in it as well. The operation of this failed VC was to turn the car into a primarily FWD vehicle, lots of front wheelspin, but it did not slip like a clutch, it just burned the front tires off. I guess if you are mistaking wheelspin for clutch slipping maybe... but I think you might be keen enough to notice the difference ;)

[DemonStreetMachine]

I have blown up a couple center diffs and it gave me a sensation of a slipping clutch, I would hit the gas and the car would free rev slightly and had a hard time getting out of its own way. That being said I was able to drive it back to Boulder from Bandimere like this (not a good idea) at highway speeds. This was on a stock 1g tranny though. I did have noise however and I believe that with all four wheels off the ground you would be able to hear or feel something going on. With the CD you have in it I have a hard time believing this is your issue.

[mitsunut]

The center diff is connected to the transfer case via the viscous coupling and the output shaft. The output shaft splines get sawtoothed from wear over the years. I didn't replace mine this last rebuild and decided to run it anyway. It also should show wear on the transfer case input gear splines. If Terry's vc is defective it will slip but in theory the front wheels should spin and the rears will not under high power. It sounds like the clutch might be slipping but without driving/riding in the car it is hard to tell. My clutch slips between 5.5k-7.5k rpm in 3rd and 4th gear. 2k miles on it, 60% is racing.
Jim.

[TerryLiv]

The center diff is connected to the transfer case via the viscous coupling and the output shaft. The output shaft splines get sawtoothed from wear over the years. I didn't replace mine this last rebuild and decided to run it anyway. It also should show wear on the transfer case input gear splines. If Terry's vc is defective it will slip but in theory the front wheels should spin and the rears will not under high power. It sounds like the clutch might be slipping but without driving/riding in the car it is hard to tell. My clutch slips between 5.5k-7.5k rpm in 3rd and 4th gear. 2k miles on it, 60% is racing.
Jim.

My first output shaft was replaced at 150,000 miles when I first started modifying my car. It now has another 70,000 on the new one. It didn't look like it was worn enough to cause a catastrophic failure when I lubed it earlier this year. If it is slipping, it doesn't do it at really low power and I haven't heard a sound like the splines are slipping past the grooves when whatever is slipping slips

When whatever slips, slips, I do not have the sensation that either end slips more than the other, as it would if my front tires spun and the backs freewheeled.

A couple of weeks ago, I did a couple of launches. It layed down 2 black tire marks, but only from the rear. Before that with a viscus rear end rather than the clutch pack, launches layed down a single black mark from the right rear. In both case nothing spun in the front.

Is that normal if the viscous coupler in the tranny is working right?

Thanks again,

Keep up the ideas.

Terry

[Cloud]

I'd be willing to bet the front spun as well, but since it is lightly loaded on a good hard launch, does not lay black marks like the heavily loaded rear tires do when they spin.

How do you like the clutch pack rear end btw?

And dumb question, but was the clutch broken in well? Meaning it definitely held hard launches before this? Also, if you abused it and got it nice and smelly it may have some warpage which makes a lot more of a difference on holding power than one might normally think.

[TerryLiv]

I'd be willing to bet the front spun as well, but since it is lightly loaded on a good hard launch, does not lay black marks like the heavily loaded rear tires do when they spin.

How do you like the clutch pack rear end btw?

And dumb question, but was the clutch broken in well? Meaning it definitely held hard launches before this? Also, if you abused it and got it nice and smelly it may have some warpage which makes a lot more of a difference on holding power than one might normally think.

Brian,

The clutch pack seems to hold better than the viscous on launches as the 2 black marks compared to 1 showed. It makes some snapping noise when making slow short radius turns to one direction, but not the other. I put some friction modifier in originally and it made a big difference. At first without it it was an embarrassment to drive in parking lots. I would have to say that for straight line acceleration it works fine. Jon wanted me to do some fast short radius turns in a parking lot, but I have not tried that yet.

I have tried very hard to not slip it to avoid the warpage and hard shifting that produces, but every once in a while I don't let it out quick enough during no lift during shifts. I don't feel I have abused it very much. My current problem is definitely not a typical over use and gradual slippage problem from over heating. It went from always holding to holding nothing at about 7000 RPM on one lightly loaded (read 1st gear) WOT event.

In other words, I think something Broke rather than wore out.

I just fixed my CV boot that came loose and ran it in the garage on jack stands. It makes so much noise that I can't hear any abnormal noise. Again all 4 wheels seem to turn at the same speed.

I am about to drive it again to see if I can learn any more.

Terry

[JSMCPN]

Dane,

The clutch pedal feels normal. Normal pressure to release it and Some free travel and a normal release when letting it out for engagement. Except there is no immediate grab as before. It just gradually slips as the car begins moving.

It is a 4 bolt and when on 4 jack stands in neutral, moving any wheel would move all the others, which was my way of determining that no axles were broken. Is it possible to have a broken axle and be able to turn other wheels when rotating the one with the broken axle?

Yes the 4 spyder still requires a viscous coupler. The 4 spyder works the same as a 2 spyder, but has 1/2 the force applied to each set of spyder gears. I have been under the opinion, Maybe justified, maybe not, that viscous couplings don't just break, but the fluid becomes gradually degraded until there is very little viscosity left. Is this correct?

Thanks,

Terry

Hey Terry, one quick thing you can check related to hydraulics is to push on the clutch release fork towards the slave cylinder. If the slave piston doesn't compress, or if it offers more than a tiny amount of resistance, then the clutch isn't fully engaging. In that situation, the master cylinder might be turned in too far.

[TerryLiv]

Did anyone notice in my first post this?

I did notice the right front outer axle boot was loose and leaking new grease?

I put new grease in the boot and a new retainer clamp and went out for a drive. It worked great until about 5000 in 2nd gear when it lost power and hit redline. Then slipped some off boost all the way home.

It was suggested that I might have an axle that was not seated, so I got under and checked them all again to find the retainer clamp off the right front that had been loose before and grease was everywhere. I turned the tire and the axle didn't turn.

Something broke in the outer CV joint of the right front axle.

Yea! I don't have to pull the tranny again. I hate putting them back in with a passion.

Thank you all for your help!

Terry

[mitsunut]

Hey Terry , glad you found it the problem.
Jim.

[mitsunut]

Did some more afr /timing tuning yesterday, no launching just wot pulls in 2nd , 3rd, 4th. No clutch slipping at all. I must have heated up my clutch/disc at the track with the back to back runs and that's what caused the slipping in 3rd and 4th. I didn't think I got the clutch disc that hot at launch but must have enough to cause it to slip a little. I wasn't looking forward to changing it out mid season. I did get the afr to 11.8 or so , car pulls hard .
Jim.