Howdy folks. I'm having problems with my clutch on the ZF that I installed into my 95 F150, and I can't help but feel that it has to do with the slave and master being from 2 different years.

The transmission/slave are out of an 89. The master is out of a 94, since Ford switched the mounting points in 92 to fix the cracked firewall problems.

I looked up online, and saw that the 1989 slave cylinder is different than the ones from the 92 and up. Im curious to know if the 94 master isn't cooperating well with the 89 slave. If that's the case, would I be able to get a slave cylinder from a 92 and newer, and have it work with the 89 transmission? I couldn't see ZF switching the slave mounts in their transmission to accommodate for a different slave. I hope that Ford just changed some things internally with the slave, like how far it pushes the throwout bearing and such.

I did notice that I have about an inch of freeplay, but the clutch is fully disengaged before I'm halfway down. I'm fearing that the newer master has a higher ratio of fluid output than what the older slave can handle. Sound reasonable? Tell me what you think!

 

I believe the only differenc is how it mounts to the firewall. The early one has the mounting holes straight up and down, the later one clocks the bolt pattern about 45 deg

 

The master cylinder bore size changed in '93 or '94, which corresponds with the change in slave cylinders. A master cylinder for a '92 would have the same larger diameter bore as was used in '89 and have the correct mounting flange for the newer firewall. I would think that the master cylinder would be a lot easier to change than the slave . One other thing you might want to check is the length of the cross-shaft lever that links the clutch pedal to the master cylinder. If it is longer than the one used with the older slave cylinders, the fluid displacement might be more similar between the large and small diameter master cylinders since the stroke would be longer.

 

See, this is why when I knew I had a problem, I came running straight to you guys. Always been there in the past, and nothing has changed.

I'm afraid I may have already done some damage. If I am doing in-town driving and using the clutch a lot, it will eventually lose all pedal. Sometimes it will go all the way to the floor, and other times it will get within 3 inches of the floor before it pressurizes. When this happens, I have to pick the pedal back up off the floor with my foot, and pump the hell out of it. If it does it when I'm not in town, I jump out of the truck, grab the pedal, and pump it. It's much easier to do it that way than with your foot. What would cause this problem?

 

Also, is there a slave/master combination that is better than the other? I'll do whatever I have to do in order to make it the best it can be. I have no problem pulling the tranny. I may pull it anyway since I'm having problems getting it into reverse without it grinding. Not a clutch issue there, sometimes it just won't go into gear. It won't grind until I let out on the clutch. I usually have to hold the shifter back into reverse and let out on the clutch until it pops in.

And actually I just realized that the master I have is not out of a 95. After looking at the pics from the parts store, it looks exactly like the one used in 1989, just with different mounting points. I'm starting to wonder if the transmission that came out of the 89 was original. It had been out before, judging by the hack job done to the floor pan. If I'm using a 7/8" bore master on an 18mm slave cylinder that mates to a 93 and newer transmission, that could explain why I have wayyy too much pedal. Going to see if I can get a year off the ZF tag.

 

If you are losing pedal either the slave or the master is going bad. If you are not losing fluid I would suspect the master, If you are losing fluid; then find where you are losing and replace the appropriate one.

I havent had a good opinion of aftermarket hydraulic clutch pieces, i.e. slave and master, as they just do not seem to last long and take forever to get right. IMHO I would just get the correct master, and slave for your year of truck from ford even if it is expensive. Just saves alot of headaches...

 

I agree with alxsnmr.

You should consider that your master or slave is failing.
If the M/S ratio were wrong it would either work from day one, or not.

There are other problems that affect the clutch release: loose firewall, pivots and linkages etc.. but these all get worse over time and aren't sporadic.

 

Well, so far I haven't seen any fluid loss. I do know that the last time I bled it, I had to gravity bleed it. If I had someone depress the pedal and then let up, it would push fluid out the bleeder screw, and then when the pedal was on its way back up, it would suck the fluid back through the bleeder and you could hear it pulling air through the bleeder. Sound like a master?

 

Sounds like you need a lesson in bleeding hydraulic systems.
That would be normal, but not the correct procedure.

 

Oops, double post.
This site has been awful the past couple of days.

 

Well, I appreciate your opinion. How about you give me the correct procedure? I was going by the Ford Service Publication CD that I have from 1992. What is your better idea?

Nonetheless, the bleeding procedure I used worked for 6 months without a problem.

I forgot to mention earlier that this problem all started after I sprayed WD40 onto the the rod where it goes into the back of the master. It was extremely squeeky, so I shot a small amount on it. Next time I drove it, I had problems.

 

You need to close the bleeder between pumps.
ie: push down, open bleeder, goes to floor, close bleeder, up-stroke, pump to build pressure, push down, repeat...

Or buy a vacuum bleeder like my Silverline Mity-Vac so you can do it by yourself.

The seals in a hydraulic system are not formulated to resist petroleum solvents like WD-40, so you may have done some damage to the M/C seals

 

I just bought a master for a 92. We'll see how it goes. I'll let ya know. Sorry if I seemed irritated earlier. Wasn't the best morning on record haha.

 

Good luck Chad,
I hope a new master solves your problems.

Do post back with your results.

 

Well, master is installed. Had to bleed it. Had problems getting it to bleed, but it did. Pedal feels good now. Easier to push, and returns much quicker than before. I would get a 1.5-2 second delay if I pushed it to the floor and took my foot off before it would return. I'll drive it more tonight and make sure she's good to go! Thanks for all your help Jim and Eric!