SPEC Twin Disk Clutch Won't Disengage at WOT - Hydraulic Line Upgrade

Transmissionintermediate✓ OP Confirmed

Problem

After installing a SPEC Twin Disk Super Street clutch kit on an R154 transmission, the clutch would not properly disengage. It was extremely difficult to shift into or out of gear, required pressing the pedal to the floorboard, and at wide-open throttle the clutch would stick and refuse to release, preventing gear changes under boost.

Transmission would not properly go into or out of gear after clutch installClutch pedal had to be pushed to the floorboard to barely disengageClutch would stick at high RPM/WOT and not allow shiftingNormal driving under ~5 psi boost worked fine but full boost caused stickingBleeding clutch system multiple times did not helpAdjusting master cylinder throw did not fully resolve the issue

Root Cause

The stock hydraulic line diameter between the master cylinder and throwout bearing was too restrictive for the SPEC twin-disk clutch. Insufficient hydraulic flow and pressure meant the throwout bearing could not fully disengage the heavier pressure plate, especially under high RPM/load conditions.

Confidence

Moderate confidence — Original poster confirmed this resolved the issue

View Original Thread →Posted May 2020 on SupraForums.com