**Fixed** ZF clutch issue - ZF driver feedback needed.

[JSmall]

I've had my ZF in for a few months now and I've never been happy with the clutch engagement. Is this common for any of you guys running the ZF?

Setup
-LUK replacement clutch
-BC Bronco kit with their 7/8" master cylinder and whatever slave cylinder they use.
-Master cylinder installed in the stock speedo hole
-Pushrod connected in the location provided by BC Bronco
-Distance from pivot point to middle of pedal = 13.5 inches
-Distance from pivot point to MC pushrod = 3.75 inches

Issues
-Clutch pedal is very stiff. Wife has a difficult time driving it. I can get over this, just didn't think this would be the case with a haydraulic clutch.

-Clutch engagement/disengagement is like a light switch...on/off. There is no feathering the clutch.

-The clutch is disengaged as soon as you push on the pedal. Maybe 3/4"-1" pedal stroke is required. Pushrod is as short as it can get with no pedal free play.

Is there any way to get more working range out of the clutch pedal? Will a smaller MC help with any of these issues? Any other suggestions that could help give me more pedal to work with? It is a pain to drive right now.

 

[Hank_]

I have the same set up and the same issue with the stiff clutch. It is not to bad for driving some but when I get in stop and go traffic it really gets to be a pain. I am sure someday I will switch to a 4r70W just because I get tired of the stiff pedal. I do not have the same trouble with the engagement though. I have no trouble feathering the clutch. Hopefully others will chime in.

Hank

 

[Broncobowsher]

Sounds like you need more pedal ratio.
Can you move the master cylinder pivot closer to the pivot on the body?
Maybe a smaller diameter master cylinder instead?

 

[Bronco73]

I bought a diaphragm zoom clutch kit for my Mazda trans swap and used all stock ford hydraulic parts to hook it up. Fabricated my own MC mount to the clutch pedal. I bet my wife could easily drive my bronco.

My only guess is that the clutch you are using may require higher pressure/effort to disengage than mine.

 

[Tcherkas]

I use an f250 master cylinder for my zf 5, the pedal has a nice amount of pressure to it and engages quick (within 3/4" of rod stroke). However my clutch engagement is also very on and off..feathering doesn't happen
I would love to hear a solution to this!

 

[Mike.thespike]

i run the the f250 set up i got out of a parts truck works perfect can feather it and super easy to use wife drives mine and has no problem at all

 

[Mike.thespike]

pics would help as well

 

[JSmall]

I have the same set up and the same issue with the stiff clutch. It is not to bad for driving some but when I get in stop and go traffic it really gets to be a pain. I am sure someday I will switch to a 4r70W just because I get tired of the stiff pedal. I do not have the same trouble with the engagement though. I have no trouble feathering the clutch. Hopefully others will chime in.

Hank

I'm thinking about doing the same. I'll do it soon if I can't get this figured out.

i run the the f250 set up i got out of a parts truck works perfect can feather it and super easy to use wife drives mine and has no problem at all

Where is your pushrod hooked up? I have mine hooked up where BC suggests, but I'm curious if that's the issue.

 

[JSmall]

Sounds like you need more pedal ratio.
Can you move the master cylinder pivot closer to the pivot on the body?
Maybe a smaller diameter master cylinder instead?

You can see from the picture that I don't have much room to raise it. What will a smaller diameter MC do for me?

 

[broncnaz]

Smaller diameter MC will give you more pedal travel and higher working prressure so you should get both more travel and easier pedal. May be able to feather the clutch as well.

 

[JSmall]

Smaller diameter MC will give you more pedal travel and higher working prressure so you should get both more travel and easier pedal. May be able to feather the clutch as well.

I guess I can give that a shot. Thanks

 

[JSmall]

Would stepping down to a 5/8 MC be too drastic of a change? Wilwood has a few that could work, but I would have to figure out how to adapt the slave cylinder line to the Wilwood MC.

http://www.wilwood.com/MasterCylinders/MasterCylinderProd.aspx?itemno=260-2636

 

[TAC71]

Ford used two different master cylinders and concentric slaves. I dont have the specs in front of me but I just changed the one in the Bronco I am currently building because the master cylinder bore was to small. My pedal ratio is right and the stroke on the cylinder is right but the output of the cylinder is wrong. I had the small bore master with the larger slave. Now it works fine. Pedal ratio on clutch is usually about 6 to 1. So moving the link up would help a lot. Or put in a 5/8 bore master.

 

[broncnaz]

I believe ford had 7/8" and 3/4" bore MC's so it may just be a matter of getting the 3/4" one. 5/8" may be a little small pedal travel may become to long before the clutch disengauges.

 

[Tedster100]

I've got a ZF & have an easy clutch pedal, I can open the door and push it with my hand. It's all F250 parts. I've had a lot of problems with air / loosing fluid so I just replaced the MC again. Got if from Advance Auto Parts and it's actually a cast iron unit, much better. I'd try the different MC as others have said, it's the easiest to do. I'm also running the BC rod and the pivot is mounted in the exact same location as yours. It may be your clutch, had a LUK brand new behind it when I was running a NP435 and hated it, lots of chatter. Put a new Ford Racing flywheel and Centerforce II clutch behind it when I did the ZF. Awesome clutch, it will feather a bit but when you dump it she's sending 100% to the driveshaft, sheared a u-joint and broke a yoke horsing around.

 

[roundhouse]

ZF clutch issue - ZF driver feedback needed.

If you used a ceramic clutch disc you won't be able to feather it at all. Ever

They grab. They don't slip

 

[JSmall]

Ford used two different master cylinders and concentric slaves. I dont have the specs in front of me but I just changed the one in the Bronco I am currently building because the master cylinder bore was to small. My pedal ratio is right and the stroke on the cylinder is right but the output of the cylinder is wrong. I had the small bore master with the larger slave. Now it works fine. Pedal ratio on clutch is usually about 6 to 1. So moving the link up would help a lot. Or put in a 5/8 bore master.

I'm really not sure what I have because it came in the BC kit. Jason did tell me that the MC was 7/8". I don't have much room to move it up because the pedal bracket will be in the way.

I believe ford had 7/8" and 3/4" bore MC's so it may just be a matter of getting the 3/4" one. 5/8" may be a little small pedal travel may become to long before the clutch disengauges.

Wilwood has a .70 MC in the same style. That's in the middle of the 5/8 and 3/4 so I could give that a shot.

 

[JSmall]

If you used a ceramic clutch disc you won't be able to feather it at all. Ever

They grab. They don't slip

I purchase the LUK 07-120.

 

[dclack]

i run the the f250 set up i got out of a parts truck works perfect can feather it and super easy to use wife drives mine and has no problem at all

X2. I pulled the trans, MC, and line all from the same 1990 F250 and used a new slave cylinder and stock clutch from O'Reillys. Works just as smooth as it did in the truck. However, my brother-in-law, used the same clutch but the MC and line kit from BCs and he is experiencing the same issue you describe. I'd suggest you just grab a used unit from a junk yard and see how it feels.

 

[broncopilot67]

I have the the wildwood master and external slave on a one to one ratio slave to master if you change that you will mess with the through. My pivot point is the same as yours have a center force clutch and I can push it in with my hand a little hard but I can do it. There is some good information on Novak site and also modern driveline. I also have this setup I got from Napa.