txdude

*** UPDATE: for the RXT, the correct measurement is 3 in-lbs. The clutch can be spun with two fingers and it'll continue moving by inertia another ~1/4 turn.

I've been debugging LS9 clutch-disengagement issues for a while now. With the pedal on the floor, I can spin the clutch by hand, but there is noticeable drag. I am trying to figure out how much drag is too much. Here are my measurements using the output shaft in 4th gear (1:1 ratio):

pedal on the floor: 35 in-lbs
3/4 way down: 70 in-lbs
1/2 way down: impossible to spin

The transmission won't go into any gear at idle, suggesting the synchros need less than 35 in-lbs of drag. If anyone has a twin-disk clutch (LS9 would be ideal, but other results are welcome), can you measure the amount of drag the clutch provides at various levels of pedal travel (engine off, 4th gear, driveshaft disconnected)? If no exact measurements are available, qualitative results would work -- e.g., can you recall being able to spin the output shaft with two fingers in any gear?

As to inevitable questions:

* Been bleeding the clutch for several weeks; the pedal has been firm from day 1; no bubbles or any change from using a MityVac;

* The slave is new and has the right shim; actually removing the shim produces the same exact torque result, which may indicate the clutch can't do better than 35 in-lbs;

* The clutch is new and has been reinstalled 3 times; nothing appears bent, the front disk has correct orientation, and the springs look good;

* The same problem surfaced with my old LS9 clutch, but I didn't take measurements then;

* The car is an 04 CTS-V; steel LS9 conversion flywheel; GM clutch & bolts

* The slave throws roughly 5/8" and starts depressing the fingers as soon as the pedal is touched; but there is about 1/4" of travel remaining for the throwout bearing when the pedal is on the floor

* With the back wheels in the air and the car started in gear, the wheels will spin in 1st, but not in 3rd; with the wheels on the ground, the car won't move (obviously, as 35 in-lbs won't be enough to push 4000 lbs);

* Conversion TR6060 transmission, first time using it

My ultimate objective is to decide if the clutch is messed up, or the transmission, and then proceed from there. If these symptoms indicate anything, I'd love to hear your theories.

punishmentcycle

iTrader: (6)

Problem is the 6060 swap.. Which bellhousing did you use.. What does it measure compared to stock.? Are you measuring your air gap correctly? With a swap you have to account for even the slightest differences in (bellhousing depth, slave used.. Clutch used.. Offset of the flywheel.. Input shaft length compared to the t56... Etc.)
My guess is the slave needs more shim but its only a guess without seeing the swap inperson. 1/4 in free pedal on these cars ive learned needs more shim and tighter airgap. Hope it helps

NIKDSC5

iTrader: (10)

The PMC master kit could solve this. The stock master cylinder is just not up to the task. I'd start there. It moves 10-15% more fluid over stock. However the measurement you're looking for should be less than 5 inch pounds in my book. 35 is a lot.

I'd also measure your clutch disc thickness. I know the McLeod twin disks send two different thickness disc. And if you have two of the wrong disc it could do this. Not sure if the ls9 is that way or not. Or possible lighten up the PP bolt torque.

txdude

Good suggestions. It's a stock CTS-V bellhousing. The TR6060 has the front plate from my old T56, so the depth at which the slave is sitting is exactly the same as before. The flywheel is a standard 6-bolt LS9.

In fact, to decouple the issue from the transmission, let's consider this -- I have a spare front plate mounted directly to the bellhousing, with a spare input shaft sticking out. I can turn the input with one hand with the pedal on the floor, but I have to grab it pretty hard -- enough for the gear teeth to leave marks on my palm.

Adding another 1/8" shim binds the clutch completely. A camera shows the fixed shaft of the slave hits (or comes really close to) the outer clutch disk, preventing it from moving back. With regard to shims, the distance A-B is 0.175", meaning a 1/16 - 1/8" shim should work. To summarize:

* no shim: 35 in-lbs
* 1/8" shim: 35 in-lbs
* 1/4" shim: would not release at all

txdude

Thanks. If the disks develop an air gap to the pressure plate (or four of them, to be precise), the drag should be virtually non-existent, right? However, when I talked to the shop that sold the LS9 flywheel, they said I wouldn't be able to spin a fully released LS9 clutch by hand. That led to confusion on my part.

I've been considering the PMC, but decided to ask if I might have overlooked something else. Trying an aftermarket clutch is yet another option, but more expensive at this point, plus I'd like to know what went wrong with the current install.

BTW, one of the LS9 disks comes embedded in the clutch and there is no way to mix it up with the other one. I don't even know if it's removable.

The PP torque is interesting. I went to 52 ft-lbs, but the amount of torque didn't seem to affect the geometry. Does lower torque on these bolts allow the clutch to release with less slave effort?

ls1247

iTrader: (2)

What kind of 6060 are using? Camaro or V2?

How about a few more details...

Thanks

NIKDSC5

iTrader: (10)

If someone said that you won't be able to move the disc by hand with the pedal depressed and the clutch disengaged that is crazy!

I was wondering how you were measuring this until now, so that's cool. And clever. Not moving though is ridiculous.

And yes. At least on the McLeod twin discs PP torque can and will effect the clamping force/geometry ever so slightly. For instance fuzzy logic stopped torquing his at 35lbs instead of 52 as that is where he found it to work best. But on the McLeod you can use a straight edge and measure how far the fingers are sunk in past the face of the PP. if that makes sense.

Like I said. I'd try the PMC first. Upgrade while possibly
Solving the issue.

txdude

The guts are from a 2011 Challenger. As the Dodge input shaft was too long, it was machined to fit (cut shorter, then a new pilot tip created). However, it later turned out the input-shaft splines were 1/2" too short for the LS9 clutch, causing the outer disk to bind. The next iteration was a 2009+ CTS-V input shaft (I think also cut shorter) whose splines are just long enough to work. The front plate and tail housing are both from my T56, machined to fit larger bearing races. Transmission dimensions are thus identical to those of a CTS-V T56.

Given previous problems with the input shaft and after taking down the transmission 6 times, I decided to mock up a setup where I could adjust the input depth by hand to rule out any spline-related interference problems. It also makes changing slave shims a 9-minute job, no wrestling required.

txdude

The guy told me a few other things -- like an LS9 clutch would never work in a CTS-V or that my slave would not be able to depress it enough. Really...

I just ordered the PMC. Let's see where that leads.

txdude

Installed the PMC a couple of days ago. The pedal got a lot stiffer, disengagement started happening earlier, but the final result is about the same:

1/2 down: 150 in-lbs
3/4 down: 35 in-lbs
on the floor: 30 in-lbs

There has got to be something I am missing.

Also confirmed on my T56 truck that a fully disengaged clutch has virtually no drag. From spinning the driveshaft, I was unable to tell the difference between the car in neutral and in 1st gear with the clutch in.

NIKDSC5

iTrader: (10)

Have you measured the clutch gap or slave spacing? To see if you need a spacer?

bmylez

iTrader: (3)

Although we have different issues, I feel your pain. Not sure if you saw my thread about my stiff pedal, but I've just accepted it. Your car is way less driveable than mine, though, so that sucks. You say that all your transmission dimensions are the same as stock, but your description sounds very very custom, and in my opinion can't be ruled out. I was actually considering getting an aftermarket clutch like you were, like the Mantic ER2 that doesn't have the self-adjusting fingers, but that's an $800 experiment. Good luck to ya.

txdude

What is a clutch-gap measurement? The only gap I am aware of is the distance between a fully compressed throwout bearing and the fingers of the clutch. That came out to 0.175", so I tried a 1/8" shim and no shim, both producing the same effect. As discussed above, a 1/4" shim jams everything up.

Speaking of fingers, I measured the distance from the bellhousing plane to 8 different fingers equally spaced around the circle. The maximum variation was around 0.040". Is that normal?

txdude

Thanks man, your stiff pedal is a saga too. I am used to a thigh workout with the clutch on my truck, which is way stiffer than the stock CTS-V. Now the PMC might have even more resistance, but it won't be an issue until I can drive the damn thing.

Taking the transmission out is annoying and the clutch master is up there as well on the list of things I'd rather never do again. That's why I don't even bother attaching the transmission, just work with a spare front plate and input shaft. This rules out any transmission-geometry issues. Do you think otherwise?

NIKDSC5

iTrader: (10)

I feel something is wrong in the clutch setup. It's acting like the discs you have are too thick.

And yeah if you measured the compressed slave that is the measurement I was looking for. I didn't feel like re-reading the thread on my phone.

txdude

I came to the same conclusion. My next suspect is the flywheel or clutch being messed up somehow. Already ordered the RXT, I'll report what I find out.

txdude

NIKDSC5 was right on -- a fully released clutch drags about 3 in-lbs. Got the RXT installed with an LS7 slave, no problems whatsoever. What a nightmare POS that LS9 clutch was.

NIKDSC5

iTrader: (10)

Right on. Glad you got it figured out! Replaced. Whatever. Now get some seat time with the RXT and launches!

txdude

Thanks man. I wish things were easy in mod hell -- now it seems the transmission clunks in gear. With the wheels up in the air, it runs fine several seconds, then a clunk. Higher gears results in more frequent clunking. No weird noise when in neutral or with the clutch pressed in. I am going to disconnect the driveshaft to rule out any possible problems with the 8.8 differential (also a brand new install, first time running).

And another problem surfaced today -- I can rev the engine in neutral, but can't seem to get past 1000 rpm when in gear and rear wheels spinning in the air. The gas pedal doesn't seem to have much effect on the RPM. The engine is a 416 LS3 stroker, also brand new. The AFR is spot on at idle, but probably something else is messed up in the tune. Need to investigate this crap as well.

AAIIIC

iTrader: (19)

That last bit could be something to do with traction control or stability control, maybe? It's seeing stationary front wheels and spinning rear wheels, so it kills the throttle. Just a guess...