ACT Monoloc Throw-out Solutions
If you didn't already know, cars like to have their issues, and Subaru isn't any different. With the introduction of the turbo model WRX's in 02-05 and the Sti model came the pull style clutch system. Just as the name states, this style clutch "pulls" while the earlier Subaru models, as well as the 06+ WRX's "push" on the pressure plate to undo the clamping of the clutch disc.
The pull style clutch has proven to be a solid design and still remains in the STI in 2017. However, for anyone who has worked on this style clutch has most likely found its flaws. To make this design work, the throw out bearing must link up to the pressure plate and be pulled by the clutch fork. To make this job harder, the only way to link the throw out bearing to the pressure plate is to do it AFTER the engine and transmission are mated together. The engineers at Subaru came up with a very innovative solution to connect the 2: a floating c-clip.
On the Left a Push style transmission (Clutch fork pushes toward bellhousing)
On the Right a Pull style transmission (Clutch fork pulls toward the tail end of the transmission)
Throw-out clip and retainer on the left, Throw-out bearing on the right
The throw-out clip goes on the clutch disc side of the pressure plate and the retainer on the other. The retainer reaches through the hole in the middle of the pressure plate and the c-clip is able to link to the retainer.
Retainer in place, c-clip in hand (looking from clutch disc side)
Clip and retainer in place
Throw-out assembly (without the pressure plate, clip is seated in groove on throw-out bearing)
Top of pressure plate view
To link the throw-out to the pressure plate, the throw-out is engaged into the plate (pushed into the plate with the clutch fork) and the clip is able to pop onto its grove. The fork is then pulled away from the clutch and the clip sets into a tapered area on the pressure plate. What this does, is the harder you pull, the smaller the diameter of that tapered area, forcing the clip into the throw-out groove with more and more force. In theory this assembly will not have issues. But is practice what is often seen is, while engaging the throw-out bearing and setting it in place, the throw-out clip becomes separated from the retainer and falls to the bottom of the bell housing. The only way to correct this after they separate is to pull the engine once again and put the c-clip back on the retainer. There are several reasons this occurs. The first is simply a weak or bent retainer which is unable to hold the clip. Another is poor pressure plate alignment with the throw-out bearing while pulling the throw-out into the tapered c-clip seat. (This is hard to countermeasure due to the fact that gravity it the main force at work for this instance) And the third is a combination of the previous 2 reasons with the addition of just poor luck. This issue is fairly easy to do, even for an experienced mechanic, it can happen to anyone!!
THE SOLUTION
Thanks to Advanced Clutch Technology (ACT) we have a solution. What ACT has done is join the retainer and throw-out clip into one patented single billet unit: ACT Monoloc. By doing this, the risk of separating the two is completely eliminated. What does this mean to us? Well, what this means is its now impossible to have our throw-out bearings separate from the pressure plate after doing a clutch job!! To make things even better ACT offers it standard with their clutch kits! Don't fret if you are already having these issues on your competitor clutch though, ACT also has you covered there! You can also buy just the monoloc kit and put it on your pressure plate!
Stock vs Monoloc Technology Top View
Stock vs Monoloc Bottom View
Monoloc on Pressure Plate
Monoloc stock photo
To purchase any of these products you can visit ACT's website here.