68RFE, check/measure the clutch release clearance

online question:

I am working on a 68RFE, and I need to check/measure the clutch release clearance. When we pull a vacuum, we can not turn the clutch. When the clutch is static, we can turn the clutch but with some friction, and we cannot get any feeler gauge to side between the clutch and the piston apply surface.

When we blow air into the turbine shaft bore, the clutch spins freely, and we can get a 0.010″ shim between the clutch and the piston apply surface. Is that how you determine the CRC?

answer

The gap between the retainer and piston in Picture one is about .040″ and is the total available travel of the piston from full release to full apply. When the gap is compressed to zero the piston has traveled as far as it can travel toward the release position. Picture two is measuring the distance from the top of the retainer plate to the top of the piston. When the assembly is not bolted to the cover this measurement represents the total travel of the piston toward the apply position. Repeat this measurement when the retainer plate has been compressed down to the piston. An arbor press is a good place to do this measurement. Add .010″ to the measurement in the compressed position and this is your target measurement for the correct release clearance plus or minus .001″ or .002″. When the unit is assembled, if this measurement is greater than your target measurement there is too much release clearance and if the measurement is less than your target measurement the release clearance is too tight.

-Found in May 2011 Newsletter