Rebuilders ‘weep’ woven clutch woes 245mm and 298mm woven carbon clutches
Do to many requests, the TCRA staff investigated the problem of woven carbon clutches plaguing rebuilders across the country. Some answers below will hopefully help in solving these mysteries.
Not a day goes by without an inquiry about General Motors’ 245 and 298mm woven carbon clutches. One of the questions repeatedly asked is, ‘What is the small hole near the clutch liner used for? And, is it necessary?’
The .018 to .024 diameter hole, shown in the smaller picture below, is used for extra lubrication applied to the carbon fiber liner during the apply cycle. Omission of this hole creates an increased surface temperature of the carbon fiber liner, which, undoubtedly, fails sooner or later. The diameter of the hole does not seem to be a critical aspect of the woven liners. Many rebuilders drill the hole up to .040 diameter with great success. Drilling a hole .018 diameter can be near impossible when compared to the drilling of a .040 diameter hole.
Another trick to successfully drilling this hole is to drill the hole slightly larger, up to .062 on an inch, and then place a 1/4 inch steel check ball on top of the hole. Then tap the ball with a steel hammer. This in effect shrinks the diameter to a smaller size. Some repeated taps may be required to meet the diameter required.
On the other hand, location is not as critical, so long as the hole is placed on the angle near the liner. However, use of a woven carbon type liner is still a must. Do not use regular paper or kevlar liners here because in most cases the converter will come back as a failure.
As for another problem, we have had inquiries about the 4T60E with the woven lining. Repeated failures are being experienced after rebuild. It has been suggested to treat these woven carbon units with care and suggest cleaning these components by hand rather than using a high pressure washing machine. The carbon fibers are far too delicate to undertake the high pressure blasts, which cause tearing of the fibers. The real solution is to remove the factory liner and clean the piston as you normally would. After cleaning, rebond with a new replacement liner.
Found in issue 08, 2003