Strange clutch / gearbox issue.
08-09-2010, 12:09 PM
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Strange clutch / gearbox issue. T56 from a 2006 LS2 GTO.
Gearbox crunches when changing from 1st to 2nd at high rpm. Can be difficult to get into 1st, often have to double-de-clutch from a standstill/when setting off. Reverse is difficult too.
When putting the car into 1st, from a standstill, the car moves ever so slightly. This is the strange part.
I have had the rear in the air, and engaged 1st gear, and the wheels turn about a quarter of a revolution when the selector is shifted into 1st with the clutch depressed, but that's as far as they turn. If I then rev the engine, with the clutch depressed and selector in 1st, the wheels don't turn. So it doesn't seem like the clutch is dragging/not disengaging properly.
I have spent a horrible amount of time bleeding the clutch, with the master cyl out of the car, and in the car. I have mostly used a pressure bleeder to force through from the top. I have a mityvac but I can't get to the feed hose out of the reservoir with it, because the reservoir is shared with the brake system on this rx7 and there's a level thing blocking access to the back. I have used the mityvac on the reservoir itself though (via a bleeder type cap).
Any ideas what's going on? Some kind of synchromesh problem? It is possible I have either a little too much or not quite enough fluid in the box, if that sounds like a possible cause..
I have altered the piston length/position on the master cylinder, to the point that I am certain the master cylinder is certainly moving the way it should. I am using the original GTO master cylinder.
Hoping somebody knows what's going on!
cheers,
Carl
Gearbox crunches when changing from 1st to 2nd at high rpm. Can be difficult to get into 1st, often have to double-de-clutch from a standstill/when setting off. Reverse is difficult too.
When putting the car into 1st, from a standstill, the car moves ever so slightly. This is the strange part.
I have had the rear in the air, and engaged 1st gear, and the wheels turn about a quarter of a revolution when the selector is shifted into 1st with the clutch depressed, but that's as far as they turn. If I then rev the engine, with the clutch depressed and selector in 1st, the wheels don't turn. So it doesn't seem like the clutch is dragging/not disengaging properly.
I have spent a horrible amount of time bleeding the clutch, with the master cyl out of the car, and in the car. I have mostly used a pressure bleeder to force through from the top. I have a mityvac but I can't get to the feed hose out of the reservoir with it, because the reservoir is shared with the brake system on this rx7 and there's a level thing blocking access to the back. I have used the mityvac on the reservoir itself though (via a bleeder type cap).
Any ideas what's going on? Some kind of synchromesh problem? It is possible I have either a little too much or not quite enough fluid in the box, if that sounds like a possible cause..
I have altered the piston length/position on the master cylinder, to the point that I am certain the master cylinder is certainly moving the way it should. I am using the original GTO master cylinder.
Hoping somebody knows what's going on!
cheers,
Carl
Last edited by carl0s; 08-09-2010 at 12:36 PM.
08-10-2010, 11:59 AM
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Thanks Mike. I used my MityVac today, by pulling off the hose that feeds the master cyl off of the reservoir, and pulling vacuum on that with the mity. I certainly got some bubbles out, but I pulled quite a bit of vacuum. Certainly more than the 10-15mm/hg that the GM tech article says to use.
I thought it had helped today, but really it's just the same.
The bottom line is, it plays up from Neutral to 1st or Reverse, and also 1st to 2nd.
I just sat on the driveway with it just now, and everytime I go from Neutral (clutch up), to clutch down then 1st, the car moves very slightly forwards. If I then keep going between the gears there's no movement, but if I pull up the clutch in Neutral, then it'll move a bit going into 1st, and be difficult on reverse.
Last night I ordered an LS7 clutch, alu flywheel and new slave cylinder from Scoggin Dickey anyway.
I thought it had helped today, but really it's just the same.
The bottom line is, it plays up from Neutral to 1st or Reverse, and also 1st to 2nd.
I just sat on the driveway with it just now, and everytime I go from Neutral (clutch up), to clutch down then 1st, the car moves very slightly forwards. If I then keep going between the gears there's no movement, but if I pull up the clutch in Neutral, then it'll move a bit going into 1st, and be difficult on reverse.
Last night I ordered an LS7 clutch, alu flywheel and new slave cylinder from Scoggin Dickey anyway.
