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Clutch Not Fully Disengaging

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I drive a 2012 Mustang GT with a Magnum XL and a McLeod RXT Twin Plate Clutch. I have been having transmission issues for a while, had some bad synchros so finally pulled the trigger and completely rebuilt the transmission from the ground up. Yesterday I reinstalled the transmission with you a new slave cylinder and also a new master cylinder. Upon driving it on my first WOT pull I felt a little nibble on the shift. Started to feel my clutch is not fully disengaging. I pulled over to the side of the road, put in in first gear and with the clutch in I revved the car. At about 6000 RPM the car starts to very slowly creep forward, so it seems that yes,the clutch is not fully disengaging at high RPMs. What do you think could be the problem? When I removed the transmission I also removed and inspected the clutch,clutch plates looked good and had good material on them. Good the problem be caused by a worn out pressure plate or just a hydraulic system that needs more time to bleed? I'm worried it is the fact the clutch doesn't correctly disengage that I ruined my synchros before the rebuild.
 
I agree. Even within our small TMO community we've seen this maybe 10 times.
 

racer47

Still winning after 30+ years
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W2W Racing
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20+ Years
SE WI
The throw out bearing can be hard to bleed. If you did not bench bleed it, there may still be a little air in the system. If you replaced the master cylinder you should have went with the gt500 version. It has a slighter bigger bore and will more a little more fluid giving you a little more clutch disengagement.

I would replace the master before shimming the throw out bearing.
 
You know that now I think about it, I have always had issues with high RPM shifts. But when the clutch was newer they were not as hectic.. Now with a newly built magnum I don't want to do any damage and experiment. Since I just replaced my master cylinder with a new GT cylinder, might be better off shimming the slave. Has anyone heard used a particular size shim with success?
 
However I just got home from driving the car, engagement starts very low, and ends near the end of clutch travel, maybe I shud work on trying to bench bleed the slave cylinder and also use vacuum on the fluid reservoir to try suck out any air in the system.
 
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Exp. Type
Circle Track
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Under 3 Years
Easton
However I just got home from driving the car, engagement starts very low, and ends near the end of clutch travel, maybe I shud work on trying to bench bleed the slave cylinder and also use vacuum on the fluid reservoir to try suck out any air in the system.
I know this is SUPER late but did you ever figure out the issue? Exact same problem on my 07 gt
 

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