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differences in clutch disconnects


New Member
Nov 28, 2011
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On the Trinity River, CA
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I own a shop here in northern California. A friend recently asked me to swap out his problematic automatic in his 91 4.0 Ranger 4x4 for a 5 speed. I pulled a trans, clutch, flywheel, clutch master and hose from a 93 Explorer. I ran into some compatibility issues, searched the Internet for some solutions, and ultimately didn't find many answers. I spent some time on different forums, looking for answers, since I did not find what I needed, I thought I would share what I learned in hope that it would help someone else.
Did you know that the updated Ford hydraulic line, which has a metal beginning, a short rubber section (which is supposed to dampen vibration in the clutch pedal so says the service bulletin I read) then a rerouted plastic section to the disconnect, is smaller on the end of the disconnect? I tried searching the web and couldn't find any information. I even called a friend who is the parts guy at a Ford dealership, and he was not aware of any differences in the clutch disconnects. The parts I pulled at the Junkyard had a new clutch, master, hose, slave & throw-out bearing. It was the new style stuff I had read about in a Ford service bulletin so I felt lucky. During the install, I lined up both of the flywheels, and found that the ring gear placement was different. I had to use the starter for a stick-shift. It is actually the starter nose which moves the gear farther from the flywheel. Since the original starter was pretty new, I swapped the nose, and kept the new motor and solenoid from the automatic.
When I tried to mount the 93 clutch master to the firewall, I found that there is a ridge on the firewall that hits the mount. In doing some research, I found that the 93 master only has a 5/8 bore. The 88-91 are the same, and have a larger 3/4 bore. I pulled a master from an 89 with the hose attached. Since the hoses looked so different, I used the 89. I put the quick disconnects side by side, and end to end, and they looked the same. Since the fluid looked dark, I tried to gravity bleed it. And like so many people on the forums have complained, it didn't work. I forced fluid out by pushing the plunger in, but couldn't get fluid to go down from the reservoir. I disassembled the master & found the ports in the aluminum piston above the cup was blocked. After cleaning, it gravity bleeds great.
After mounting everything, I found that the disconnect would not quite lock into the updated slave. It would come within 1/8 of locking, but would not quite lock. I measured everything I could, and decided that it was some kind of mismatch between the updated slave and the old style coupler.
I got lucky, and the updated line was still at the junkyard. When I measured the 2 parts I found that the updated coupler is .025" smaller only on the very end where the o-ring is, the o-ring is slightly thicker too. Where the line goes into the master,the line is the same. So I changed to the newer line. I found several people on different Forums which were having problems with couplers leaking, and had changed the line several times. The problem is a mismatch in the couplers.
WARNING If you have an old slave, and you buy a new line with the updated parts, the coupler will connect, but the sealing end could be .025" too small. The o-ring may or may not seal for a while. Then it will surely leak. I searched the web for hours, and could not find this information. There is a difference in the hydraulic clutch line disconnects. Since I had the old line, with the new slave, it would not connect. If it would have been the other way around, it would have connected and leaked. You better measure the old and new parts, or replace them as a set.
When I swapped the transmission, I replaced the wire harness for the transmission up to the left fender connectors. This connected the backup lights but did not satisfy the neutral sense circuit on the 4x4 computer, so it would not shift into low range. There was an unused neutral switch on the trans, connected into the harness that I had changed that I connected to a ground, and to the R/W sense lead that was right in that same connector on the fender. If I had used a 91 harness it might have worked by itself.
I could not find a stickshift computer so the automatic ECU is still in there. If I ran a KOEO self test it noticed that there was no torque converter lock up solenoid or 3/4 shift solenoid. So, I tricked the ECU into thinking they were there by wiring in a couple of 10,000 ohm resisters between the original power supply to the trans and the leads that went to the solenoids. Again, these were on the fender where I changed the harness to the transmission. After driving it around for a week, I did not get any check engine lights or drivability issues with the automatic computer. The only problem might be smogging it here in CA. When I monitor data from a scanner, it says P/N with the clutch in, idles slightly faster & uses less timing, which would help with its emissions. With the clutch out it says it is in D/R idles slower with 5 deg more timing. Were talking 100 rpm here. He will just have to smog it with the clutch in.
One last thing, if someone was installing an auto where a stick was, there was a cap on the harness to the clutch interlock switch when I installed it, I noticed that the cap had jumpers in it allowing the automatics neutral safety switch to work. Without the jumpers in the cap, the starter wouldn't work.
I hope this information helps someone trying to do this, or who has a problem with a leaking clutch disconnect.
I put an injected 5.0 HO in my old beatup 65 3/4 ton pickup, so creative wiring solutions are normal for me. What a sleeper! and it gets 20 MPG

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