Problem shifting above 4k rpm
Thread Starter
Heel & Toe
Joined: Jun 2013
Posts: 19
Likes: 0
Problem shifting above 4k rpm
I've got an annoying problem with shifting above 4000rpm at speed.
If I free rev the engine while standing still I can hit all the gears at even 6500rpm but as soon as I am rolling (did a test at 30mph) BAM, a wall. Impossible to shift to the next gear until the rpm has dropped.
The car is a Z06 with Spec Stage3+ clutch, "upgraded" MN6 gearbox, don't know anything more about it, BPP shifter and a Tilton master cylinder adjustable to the same height as brake pedal. The clutch is releasing at the top of the travel and it doesn't roll forward when I try to rev it in gear with the clutch down.
Anyone got an idea of why it does this? Makes it impossible to be competitive at racing with over second long gear changes
If I free rev the engine while standing still I can hit all the gears at even 6500rpm but as soon as I am rolling (did a test at 30mph) BAM, a wall. Impossible to shift to the next gear until the rpm has dropped.
The car is a Z06 with Spec Stage3+ clutch, "upgraded" MN6 gearbox, don't know anything more about it, BPP shifter and a Tilton master cylinder adjustable to the same height as brake pedal. The clutch is releasing at the top of the travel and it doesn't roll forward when I try to rev it in gear with the clutch down.
Anyone got an idea of why it does this? Makes it impossible to be competitive at racing with over second long gear changes
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
i zoned in on "spec clutch" big majority of clutch problem threads have those two words in them
where does your pedal engagement come on? is it right off the floor? you may try changing the release point a bit higher. sounds like the clutch is barely disengaging
where does your pedal engagement come on? is it right off the floor? you may try changing the release point a bit higher. sounds like the clutch is barely disengaging
Thread Starter
Heel & Toe
Joined: Jun 2013
Posts: 19
Likes: 0
That's what I thought first, hence the tick master. Before the tick I had forward roll at rev limiter. The clutch disengages almost right away when depressing the pedal. It's completely disengaged around or before half the pedal travel.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Try this. Im leaning toward you having TOO MUCH master cylnder adjustment. It may be over traveling the pressure plate fingers.
Jack up the rear of the car (wheels off the ground) Make sure that the drive train is at normal operating temps. Engine running trans in first gear.
Back off your master cylinder adjustment rod until when you depress the clutch, it no longer disengages the drivetrain. Rear Wheels rotating
Adjust the master cyl adjustment rod until when you depress the clutch, it no longer turns the rear tires. A little creep isnt abnormal.
Once you get to that point, add an additional 1/2 to 3/4 of a turn on the adjustment rod and see if that helps. Dont forget to lock down the rod with the lock nuts when your are done adjusting
I also recommend that you do a really good clutch cylinder /slave cylinder bleed and make sure that all the air is out of the system!
Jack up the rear of the car (wheels off the ground) Make sure that the drive train is at normal operating temps. Engine running trans in first gear.
Back off your master cylinder adjustment rod until when you depress the clutch, it no longer disengages the drivetrain. Rear Wheels rotating
Adjust the master cyl adjustment rod until when you depress the clutch, it no longer turns the rear tires. A little creep isnt abnormal.
Once you get to that point, add an additional 1/2 to 3/4 of a turn on the adjustment rod and see if that helps. Dont forget to lock down the rod with the lock nuts when your are done adjusting
I also recommend that you do a really good clutch cylinder /slave cylinder bleed and make sure that all the air is out of the system!
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
based on what you said i agree with bill, seems the most logical.
either that or it's the clutch
internet is littered with spec clutch out of balance, hard shifting, not working right threads.
either that or it's the clutch
internet is littered with spec clutch out of balance, hard shifting, not working right threads.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
LOL.. I have the SPEC Twin disk and have no issues at all!
KNOCK ON WOOD!!!
I was also VERY careful and went thru great pains to get every detail perfetc from shim measurement to flywheel balance.
BC
KNOCK ON WOOD!!!I was also VERY careful and went thru great pains to get every detail perfetc from shim measurement to flywheel balance.
BC
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