Hyd. clutch issue

[Mike Holleman]

I'm just getting my car to be mobile and the clutch is releasing way too low. T56 with stock GM master and slave. Clutch is an LS7 unit. It seems to be bled but the release point is just off the floor. Matter of fact reverse requires shutting off the engine and restarting in gear. I could use some advice on what to look for and how to improve it.
Thanks
Mike Holleman

[Mike Holleman]

I'm just getting my car to be mobile and the clutch is releasing way too low. T56 with stock GM master and slave. Clutch is an LS7 unit. It seems to be bled but the release point is just off the floor. Matter of fact reverse requires shutting off the engine and restarting in gear. I could use some advice on what to look for and how to improve it.
Thanks
Mike Holleman

Bump
Anyone have a suggestion.
Mike

[derekf]

Don't most folk have to modify the stroke on the stock GM masters? I believe that Tyler (ATS) provides it as a service but I'm not all that sure what he alters.

[WILWAXU]

From what I've read, ATS shortens the piston rod. If you just bolted in a stock f-body master to a stock pedal assembly that might be your of your problem.

[TheMonkey]

how is pedal effort?

if effort is easy, mebbe your pedal ratio is too big. if you lower your attachment point to the pedal arm, your clutch will disengage sooner (higher), but pedal effort will increase.

larger bore hydraulic cyl would effectively do the same thing.

[Mike Holleman]

OK. The pedal assy. is a stock 65 Chevelle modified to work with the stock GM master. Effort is about the same as most hyd. clutches I have experience with. The mod I did was as directed by Street and Perf. I am fully stroking the stock master but limiting with a stop the travel to 15/16" as per S and P. The master and slave are GM matched items, built to work together. I'm getting ready to rebleed the system. I am using LPP's remote bleeder.
Thanks for the feedback. I'll repost if the rebleed helps.
Mike

[TheMonkey]

if you are spec'd okay on stroke & bore, then must be something else. is your hydraulic TOB installed with bleed hose on top or bottom? bleed should be on top and supply on bottom, otherwise can't get all the air out.

[Mike Holleman]

Bleeder on the top. I couldn't get to the clutch today for dealing with other issues. Manana.

[andrewb70]

Mike,

I would do the "turn the driveshaft by hand test." With the engine off have a friend get under the car and start to attempt turning the driveshaft while you slowly press the clutch. Do this in 4th (1:1) gear. This will give you a good idea where the clutch releases. After the point at which the driveshaft can be turned by hand, you want another inch or inch and a half of pedal travel.

If you are using a 2002 f-body MC it has a 3/4" bore. 96-97 MCs mount the same way but have a larger 7/8" bore. This might be your solution to increase throw out bearing travel. But do the test first.

Andrew

[Mike Holleman]

Mike,

I would do the "turn the driveshaft by hand test." With the engine off have a friend get under the car and start to attempt turning the driveshaft while you slowly press the clutch. Do this in 4th (1:1) gear. This will give you a good idea where the clutch releases. After the point at which the driveshaft can be turned by hand, you want another inch or inch and a half of pedal travel.

If you are using a 2002 f-body MC it has a 3/4" bore. 96-97 MCs mount the same way but have a larger 7/8" bore. This might be your solution to increase throw out bearing travel. But do the test first.

Andrew

Good suggestion. Right now it is releasing within the first inch from the bottom. It is a GM #12570277 master. Master and slave were bought together. Hopefully I will find extra air in the system today and will gain a little pedal.
Mike

[Mike Holleman]

Got a little bit of air out but the clutch is still releasing very low. Once I can drive it abit I'm hoping it will improve.

[andrewb70]

Got a little bit of air out but the clutch is still releasing very low. Once I can drive it abit I'm hoping it will improve.

Mike, these things aren't like fine wine. They don't get better with age. I would suggest getting the 7/8" bore MC from a 96-97 f-body.

Andrew

[Mike Holleman]

Mike, these things aren't like fine wine. They don't get better with age. I would suggest getting the 7/8" bore MC from a 96-97 f-body.

Andrew

I guess I was hoping that once the disc seated it would improve.
Do you know from the part number I listed that my master is a 3/4 bore? And secondly do you have the P/N for the 7/8"

Mike

[andrewb70]

I guess I was hoping that once the disc seated it would improve.
Do you know from the part number I listed that my master is a 3/4 bore? And secondly do you have the P/N for the 7/8"

Mike

Mike,

I am not familiar with any GM part numbers. If the part number that you listed was for an LS style MC, that is 98-2002, then it is for use a 3/4" bore. If you go to Rockauto.com you can look through their catalog. It lists various options and the bore for the MCs.

For some reason the way that the pedal and rod are positioned in an a-body it does not allow full travel on the MC. I am using the Keisler kit that uses a Gerling style, Wilwood MC and it has a full 1.4" stroke. This gives plenty of MC travel. So much in fact that I was able to decrease the size of the MC from .750" to .700". This gave me a softer pedal and also kept the TOB from traveling too far. You can click on the link in my sig for more details. I am not using a T56 or a stock throw out bearing, but the functionality is the same.

Andrew

[Mike Holleman]

I do believe it is for the 98/02 as you said. It is definately getting fully stroked. The stroke on this unit is 15/16. You have to limit it to this stroke or you will push the bottom out of the plastic housing. Mark at speed and perf. warned me of that. I modified my pedals by his drawings but came up with my own adjustable stop. I'll check into the unit you are recommending. Gotta have good clutch action.
Thanks for the input.
Mike

[andrewb70]

I do believe it is for the 98/02 as you said. It is definately getting fully stroked. The stroke on this unit is 15/16. You have to limit it to this stroke or you will push the bottom out of the plastic housing. Mark at speed and perf. warned me of that. I modified my pedals by his drawings but came up with my own adjustable stop. I'll check into the unit you are recommending. Gotta have good clutch action.
Thanks for the input.
Mike

Mike,

I too have heard that the TOB can be pushed out. The thing is that your clutch is obviously dragging. If it was an aftermarket clutch then you may have to install a shim between the MC and trans. But you have an LS7 clutch and the installed height on those is the same as the earlier f-body clutches. I suspect that you might need just another 1/16" travel at the MC to release the clutch completely. I really hate the fact that there is no inspection cover on the LS bellhousings. It would be so nice to see what the clutch is doing. Do it old school style with a feeler gauge. I have seen people drill big holes in the bottom of the bellhousing just for that purpose.

Good luck. Let us know how it works out.

Andrew

P.S. Do the "spin the driveshaft by hand" test.

[WILWAXU]

I've been researching a Keisler master cylinder on my Nova. Keisler says that it bolts right into car and will work with the stock f-body TO bearing.

[Mike Holleman]

[quote=andrewb70]Mike,

I too have heard that the TOB can be pushed out. The thing is that your clutch is obviously dragging. If it was an aftermarket clutch then you may have to install a shim between the MC and trans. But you have an LS7 clutch and the installed height on those is the same as the earlier f-body clutches. I suspect that you might need just another 1/16" travel at the MC to release the clutch completely. I really hate the fact that there is no inspection cover on the LS bellhousings. It would be so nice to see what the clutch is doing. Do it old school style with a feeler gauge. I have seen people drill big holes in the bottom of the bellhousing just for that purpose.

Good luck. Let us know how it works out.

I have a McLeod SFI bellhousing. You could look in from the side if the tunnel was bigger. I'm not sure I'm following you on the shimming. Where would you shim to gain clutch release?
I will be playing with it more today trying to get a handle on it.
Mike

[Mike Holleman]

I've been researching a Keisler master cylinder on my Nova. Keisler says that it bolts right into car and will work with the stock f-body TO bearing.

Let me know how that pans out.
Mike

[Mike Holleman]

Mike,

I am not familiar with any GM part numbers. If the part number that you listed was for an LS style MC, that is 98-2002, then it is for use a 3/4" bore. If you go to Rockauto.com you can look through their catalog. It lists various options and the bore for the MCs.

For some reason the way that the pedal and rod are positioned in an a-body it does not allow full travel on the MC. I am using the Keisler kit that uses a Gerling style, Wilwood MC and it has a full 1.4" stroke. This gives plenty of MC travel. So much in fact that I was able to decrease the size of the MC from .750" to .700". This gave me a softer pedal and also kept the TOB from traveling too far. You can click on the link in my sig for more details. I am not using a T56 or a stock throw out bearing, but the functionality is the same.

Andrew

Andrew, I did some checking last night on the master you suggested.
My master has the hose to the release bearing fixed and it is a GM style quick disconnect. Is the 96/97 the same or can it be changed to the quick disc.?
Mike