Clutch issue I can't figure out

[ThomasL]

After about 10k miles on my McLeod RXT, I noticed it slipping when I'd accelerate in higher gears. I'd go WOT and even just half throttle and RPMs would shoot up but the car didn't go anywhere. So i figured maybe the clutch was on it's way out. It still cruises around town and shifts just fine at lower RPM. So, I ordered a brand new RXT, new OEM slave assembly, OEM pilot bearing and OEM flywheel just to make sure I had a fresh clutch and good supporting parts too. Fresh fluid as well and everything buttoned up as it should be. The new parts and clutch are installed and sure enough, same issue. This leads me to believe it is certainly not the clutch itself, but somewhere there is an issue that just has me stumped as well as the shop doing the install. Same setup and power (800rwhp) as the previous RXT which ran fine for over 10k miles. The funny thing is, when the old clutch was pulled, it appears to still have plenty of life left in it too. Any ideas or suggestions?

System consists of all OEM parts aside from the RXT and a SS clutch line.

 

[ThomasL]

I'll also add that the clutch pedal engages very high as well; as it did previously on the old clutch/parts.

 

[07 Black Beauty]

Any odd noises? Any work done to the rear end?

 

[Ghoust]

Belt slip?

 

[ThomasL]

Any odd noises? Any work done to the rear end?

Nothing odd. Cruises around town fine. Any excessive throttle and RPMs shoot up, clutch squeals and the speedometer doesn't move.

Belt slip?

I don't think so. Good thought though.

 

[Snoopy49]

Could the clutch slave unit be to long and not have enough clearance between the throwout bearing and the pressure plate?

 

[ThomasL]

Could the clutch slave unit be to long and not have enough clearance between the throwout bearing and the pressure plate?

That's what it seems like, but we're stumped as to why the slave length is an issue all of the sudden if that is the case. We're focusing on the master cylinder and clutch line for now. Those seem to be the only two things unchanged from the old clutch to the new.

 

[Bad Company]

If upon inspection of the old clutch you didn't see signs of the clutch slipping. The only other thing that it possibly could be is the driveshaft. With your car being a 2014, the driveshaft is a carbon fiber tube. At each end of the tube is a press fit splined/knurled hub. Inspect each end of the carbon fiber tube of the driveshaft for evidence of slippage of the press fit hubs.

What you are describing sounds exactly like clutch slippage. But if the clutch isn't the source of the problem and everything else is a steel on steel mechanical gear mesh. This only leaves the carbon fiber driveshaft tube and it's press fit hubs as a possible cause for what you're explaining

 

[ThomasL]

If upon inspection of the old clutch you didn't see signs of the clutch slipping. The only other thing that it possibly could be is the driveshaft. With your car being a 2014, the driveshaft is a carbon fiber tube. At each end of the tube is a press fit splined/knurled hub. Inspect each end of the carbon fiber tube of the driveshaft for evidence of slippage of the press fit hubs.

What you are describing sounds exactly like clutch slippage. But if the clutch isn't the source of the problem and everything else is a steel on steel mechanical gear mesh. This only leaves the carbon fiber driveshaft tube and it's press fit hubs as a possible cause for what you're explaining

We're going to look into that. Thank you.

 

[Bad Company]

For a simple test of the driveshaft. Get a white Paint Pen and make two index marks on each end of the tube and there corresponding hubs. Drive the car and replicate the symptoms. then re-inspect the driveshaft to see in the paint marks are still indexed in the original locations between the aluminum hubs and the carbon fiber tube. If they are not. Then you know it is the driveshaft causing the issue and not clutch slippage

 

[Bad Company]

We're going to look into that. Thank you.

You're welcome

 

[ThomasL]

For a simple test of the driveshaft. Get a white Paint Pen and make two index marks on each end of the tube and there corresponding hubs. Drive the car and replicate the symptoms. then re-inspect the driveshaft to see in the paint marks are still indexed in the original locations between the aluminum hubs and the carbon fiber tube. If they are not. Then you know it is the driveshaft causing the issue and not clutch slippage

We'll do this tonight and see what it shows. Thanks again

 

[VFORCEJOHN]

I have a RXT in mine now, same issue . it lasted as long as the stock clutch with chattery engagement.

I can accelrate hard in 1-2, Maybe 3rd gear. 4th gear up won't hold at all. No smell, but obvious slippage. I'm "only" at 700rwhp

I toasted the stocker, Quarter master double, RXT double. Now I have the Triple Ace ready to go in but dealing with shimming issues (just got the tool in this week to set the shims. If this don't hold... I'm getting an automatic...

FYI. I also LOST 2 tenths in the 1/4 mile and 2-3 mph with the RXT. Mainly due to the weight. the 1/4 master clutch revved like it was a 5.0 boss motor very fast response and easy to pull out but it ate the fiber discs right up and destroyed the clutch in just 2-3 hard launches.

 

[ThomasL]

I have a RXT in mine now, same issue . it lasted as long as the stock clutch with chattery engagement.

I can accelrate hard in 1-2, Maybe 3rd gear. 4th gear up won't hold at all. No smell, but obvious slippage. I'm "only" at 700rwhp

I toasted the stocker, Quarter master double, RXT double. Now I have the Triple Ace ready to go in but dealing with shimming issues (just got the tool in this week to set the shims. If this don't hold... I'm getting an automatic...

FYI. I also LOST 2 tenths in the 1/4 mile and 2-3 mph with the RXT. Mainly due to the weight. the 1/4 master clutch revved like it was a 5.0 boss motor very fast response and easy to pull out but it ate the fiber discs right up and destroyed the clutch in just 2-3 hard launches.

It's frustrating for sure. Like i said, the issue popped up seemingly out of nowhere after roughly 10-12k miles on the old RXT and continued onto the brand new RXT. I'll keep updating this as we figure it out. Driveshaft test tonight to see where that stands, and then new OEM line tomorrow as well as new OEM Master Cylinder if needed. Beyond all that, we can't think of any other potential fix at this point. Possibly an adjustable slave but we'll deal with that if needed.

 

[2011 gtcs]

Definitely seems like a slave cylinder issue to me. It could definitely be the Drive shaft, but I still would be leaning towards the slave cylinder. Make sure there isn't possibly a air pocket in the hydraulic line.

 

[VFORCEJOHN]

It seems as if you slip these units ONCE in a drag race scenario launch. the heat generated will instantly toast he clutch and release clamp load plate spring tension on the unit. That's when I toasted mine. Drag racing at MIR. 2 years in a row I drove home slippin.

 

[VFORCEJOHN]

I'd also doubt the driveshaft slip. if Carbon fiber slips it's instantly frayed to nothing.

 

[JUIC3D]

If there was air in the line, the issue would be the opposite - it would not disengage at all. There would be insufficient pressure behind the slave to press on the fingers of the pressure plate.

The clutch is brand new so it has not been toasted at the drag strip.

 

[JUIC3D]

The slave is brand new. The issue is the same from old clutch to new. That leads me to believe it's something that has not been addressed, clutch line or master cyl.

 

[ThomasL]

Can confirm it is NOT the DS. So that's good. New OEM line is next up tomorrow.