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Discussion Starter #1
Hello everyone needing some help/advice. I have been fighting this spec clutch since first install and the list of issues keeps growing.
-MK3 Supra
-Rebuilt R154
-Spec Twin disk clutch
-Willwood master cylinder
( SPEC Super Twin Dual Disc Clutch Kit 1987-1992 Toyota Supra MK3 SS Trim )

Had to drop the transmission twice for this clutch so far, afraid its going to need another drop to fix the problem. I went ahead and did the 500mile break in period of the clutch. Smooth engagement and shifts, no problems. Yesterday was when i finally gave the car some big pulls on the highway. The problem is when i am in high rpms/boost the shifter seems to get stuck in the gear. 1-3 gear i can pull it out after rpm's drop. 4-5 gear pulls its a bitch to get out and then it will only go back into the same gear. Only fix is to slow car down and then i am able to get into other gears. The previous clutch had no problems like this (single disk) and the transmission ran fine. I have bleed the lines 3-4 times as well. Originally had to drop the transmission to shim the throwout bearing>(which spec said was not needed "plug and play")

Any advice would be extremely helpful. I'm about to throw this spec clutch out of a window. I want to emphasize its smooth as butter when not driving in WOT or full boost.

I posted a video of what it looks like getting stuck in first gear. 5th gear looks the same, but once pulled into neutral it will only go back into the same gear it came from.
 

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3/4" master cylinder?

It's usually a MC issue when the clutch won't disengage at higher RPM. 2nd guess would be the slave cylinder. For a while the SPEC slaves had a reputation for the seal blowing out and leaking enough to cause the clutch not to disengage.
 

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boost'en down 101
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You could try reducing the free play to where it has just enough its not constantly putting pressure on the master cylinder. This will give you the most travel in the master cylinder. If you do get sick of the spec I'd recommend picking up a clutch from rhdjapn.com. That's where I got my os giken twin disk and movement alteration kit. Their prices and selection is better than any store in the us. Just look for 1jz clutches they have os, exeddy, orc, ect, and replacement parts....
 

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Discussion Starter #4
Sorry for the late updates, this corona virus mayhem has got all over the place. I want to continue documenting my findings as i'm noticing online this isn't a uncommon problem with spec clutches... I went ahead and spoke to spec again and they believe the clutch is just to heavy for my "old" transmission..."apparently" i'm not sure how much i believe this due to the fact i know a few people running very similar hp to mine, along with same exact clutch, master, and transmission. I've already maxed out the linkage for the clutch pedal, going to try a few other ideas out i have and get back.

I went ahead and attached a video of it engaging and disengaging. I cant imagine its gonna "free spin" due to being connected to the input shaft etc...

 
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