I’m in the middle of some winter work on my 360 and I’ll be replacing the clutch release/throw-out bearing amongst a few other items. There is a possibility I may replace the clutch also depending on the condition when I remove it for inspection. TCU says 30% worn but it looks to be worn more visually. Here’s a picture of where I’m currently up to.... Image Unavailable, Please Login I’ve watched what the clutch position does in neutral and as gears are selected and sketched this.... The clutch is open in N and closes a couple of mm as a gear is selected but still beyond the PIS value. The clutch closes on throttle application. Image Unavailable, Please Login The question I have is what is the purpose of the new clutch closed position other than a reference point for clutch wear? I’d expect the current clutch closed position to be important parameter with which the clutch control is referenced, as this increases with wear moving away from the new clutch position. I struggle to see why it is important other than to indicate wear and as a check to make sure the current clutch position isn’t lower than it. The wear index value is clear to me.
I think I’ve answered my own question by looking in a few pages from a late WSM I have. It says something to determine the clutch wear trend the TCU must contain information from when the clutch is new and closed.
would you confirm that I understood your diagram correctly? 1. Right hand side is the flywheel and left is the clutch. 2. when neutral, the frontal surface of the clutch is at 10mm 2. 8.63mm is what you got when you measure a new clutch disk.
Imagine the clutch and flywheel are both on the far left and the gearbox on the right. The scale is along the gearbox primary shaft that the release bearing is mounted upon. The clutch release bearing sensor provides a position in mm and for the sake of this exercise, let’s assume it is referenced (0mm) to a position close to the flywheel. As the release bearing moves to the left, towards the flywheel, the clutch opens. When it moves to the right, away from the flywheel, the clutch closes. The relative movement of the release bearing to the actual clutch is amplified by the mechanical advantage of the pressure plate. Eg if the release bearing moves the pressure plate fingers by 10mm, the clutch pressure plate may only move 1mm When the clutch is new, the clutch closed position is as close to the flywheel as it ever will be. As the clutch wears the current clutch closed position increases as the pressure plate has to move closer to the flywheel, meaning the release bearing is further away from it. On the diagram above the new clutch closed position entered into my TCU is 15.94mm. The current clutch closed position is around 18.5 mm which equals about 30% worn. If I watch the clutch position. In N the release bearing position is around 10mm and the gearbox primary shaft isn’t rotating proving the clutch is fully open. If I select any gear, the release bearing moves a couple of mm away from the flywheel closing the clutch slightly. I call this a pre-engage position. The PIS on my car is set to 4.6mm so in theory my clutch should start to engage when the flywheel is 4.6mm from the current closed position ie 18.5mm - 4.6mm = 13.9mm. What I see on my car is a slight creep sometimes when in gear or reverse even though the clutch position is at 11.75mm. I’m replacing the release bearing as it’s noisy and once I get a clutch alignment tool from HE I will split and inspect the clutch also. What it also tells me is you cannot set the PIS based on the gearbox primary movement as the clutch is further open in N than in gear and when it is in gear the primary cannot move, as it is locked by the wheels. I hope this helps and don’t take it as official or accurate as it’s only what I’ve learnt from various non-official sources. Sent from my iPhone using Tapatalk
