It is time to talk hydraulic clutch systems.

I know, everyone's favorite subject, right?

So my 85 460, t-19 cab chassis bucket truck. Made it to Oregon, no problems at all. 2 days, truck performed flawlessly. Day 3, couldn't get the clutch to work.

Drove it 800 miles freeway, 2 days through Portland traffic, at least 200 miles stop and go commuter traffic, so 1k miles total. Day 3, I walk out to my hotel, go to start the truck, can't get it into gear, at all.

Start it in 1st gear, clutch will not disengage, tried to get through the day. In gear with the clutch pedal to the floor, it will idle, barely, but not enough to shift gears.

Spent 3 days trying to fix it in a hotel parking lot. First day, found no bushing, badly worn ring going into the master cylinder, pedal bracket peg was worn down to the point it was ready to snap off.

I hammer out the little splined peg, add a 3/8 bolt and bronze bushing (had to walk to the hardware store, got what would work). Took care of at least 1/2 of play in the pedal, figure I am good right?

Put it all back together, and exact same issue. Can't shift, starting in gear with clutch pedal to the floor, it still is dragging enough to move the truck. It's better, and close to working, but not good enough. Fluid is full, no apperent air in lines. Figure maybe I need to tighten down that loop. Spin it in 2-4 threads. Pedal feels solid, push down on the clutch, and linkage to the master breaks right at the jam nut.

So, I walk down to the closest parts store, but a new master cylinder. Of course I really just wanted to push rod, but this one is a different style, non removable pushrod.

I end up swapping in the new master, tried to bleed the system by myself. Working in a cold rainy parking lot with limited tool, spent two more days getting parts and trying to bleed it, never got it to work, gave up and drive home.

Made it 1000 miles back with no clutch, Rev matching for shifts. Big hills sucked because of how difficult down shifting was, few mountain passes were only 20-25 mph once I got it into gear. 12 hour drive took 22 hours, but we got her home.

So now I have a brand new clutch, (2000ish miles before leaving for Oregon), new master cylinder, maybe air in the lines (needs bled). Get a helper to bleed it and try to work the air out. Pretty confident it is totally bled out, but still not working right.

Decided the slave must have given up while in Oregon, it's the only not "new" replaced part left in the system. So I replaced the slave cylinder.

Pedal never felt right with the new slave cylinder. After hours of bleeding, clutch still doesn't release fully figure it must be a bad replacement slave right? I have had bad parts store brake master cylinders, took 3 before I got a good one on my thunderbird a few years ago.

This time, I am sick of messing with it, the one I replaced was the cheapest one, because it was the only one availble in stock. After 3 days on my back covered in brake fluid in the rain/snow, I decided I will just bite the bullet and order the more expensive slave cylinder. It finally comes, much happier with it, all metal, seems higher quality, swap that one in. I never got more then half clutch pedal. Bottles of brake fluid ran through bleeding it, still no change.

I gave up, took it to a shop, told them it needed to be bled or something, shop said they had a power bleeder. Later that same day, I call to see if they have been working on it, they say no, we can't bleed it, because the first time we hit the pedal, the clutch fork fell out and we can't get a new one.

Drive it home, still no clutch, no charge from the shop, but still a bit working clutch.

I crawl under the truck, clutch fork is gone. Find it on the floor if the truck under the seat. One of the two "forks" is busted completely off. Shine a light in the bell housing, pressure plate fingers are all mangled. Pretty sure they removed the fork, jammed it back in, in front of the throw out bearing, tried to start it and it got caught in the pressure plate.

I am in the process of pulling my "new" clutch and pressure plate. Still never felt like I got the lines bled because I never got full travel out of the pedal.

So I am just checking rock auto, looking at parts, thinking about picking up a zf 5 speed. Should bolt in, I wouldn't mind overdrive while I got it all taken apart, curious what it might cost.

Well, the 86ish to 88 seem to be basically bolt in, same master cylinder, same clutch plate ECT. So I check the slave/master cylinders for 86-88 applications and find something interesting.

88 all models have the 5 speed optional, for all engines. F-150's have the Mazda trans, 460/diesel have the zf trans, all models still list the 4spd t-18/19 as an option, then I noticed something interesting.

Regardless of year, all master cylinders have the same ".880" or 22mm sized master cylinder.

All external slaves are listed for all models, years and transmissions stating that they can be used with either the 4 or 5 speed. Cool, should be okay and okay right? Wrong.

There is a difference in slaves. Same clutch fork, same master, so we can assume that travel is the same. But even in the same applications, randomly one slave with be a 1.25" bore. Another is a 1" bore, another is a "19.05mm" or roughly a .750" bore.

I think I have a 1.25" slave, in a system designed for either the 1" or .750" slave, and I think this is why I do not have full clutch pedal. It only seems to go half way, then it stops moving.

So school me on these hydraulic systems.

I have a 1985 t-19 with a 460. Master should be the ".880" bore acrossed all models. Now, should I have a .750" slave, the 1" slave, or the 1.250" slave?

I no longer think my issue is bleeding the lines, I think the slave cylinder is too large if a bore, which is why I only get half a pedal.

Am I crazy? Anything I am missing? I plan on taking apart the two slaves I have right now, pull the snap ring and measuring the bore, that will at least tell me if I received the same bore last time, but I think the nice big metal slave I paid extra for is a 1.25" slave, and I think I need either the .75 or 1" slave. If it should be a .75 and I have a 1.25 with the same stroke, that gives me a 60% fluid exchange with the same pedal travel, and I feel like that is why I can only get a half pedal no matter what I do.

Hoo boy!
I have traveled this path before!

The Windsor Zf uses a concentric slave bolted to the back of the bell housing and NO release arm.

The Zf has a bigger diameter (1 1/4") 10 spline input shaft.
You need a new clutch disc for it to fit.

Did the metal slave cylinder have an actual bleed nipple on the front(top)?
I have an Excedy SC886 slave for a T-18 in a 351 and it fits everywhere, but I can take a piece of vinyl hose and run it up, right back into the master cylinder. https://a.co/d/ecDoKf6
When I bleed, I'm just pumping the fluid in a loop!  💡

BTDT, BTTS with the stud on the belcrank.
I rifled the truck and found a 9mm shell casing....
Walked to the hardware. Bought some JB Quick, a couple of washers and a circlip that fit the extractor groove.
Yeah, that was fun, but it got me home!  😉

I'm here for you!
I'm that savant who's taken one of these to pieces in the dark and reassembled it with their eyes closed like field stripping a damn M1 Garand.  😂
"This is my rifle, this is my gun...". Have a grin and a gold star if you know exactly where I'm coming from...

Nope, no bleed nipple on anything I have been able to source. Just the hole in the rough casting by the bleed screw. I seriously considered drilling and tapping an not fitting to add my own...

I have found a way that seems to bleed everything first time similarly to reverse bleeding though.

Remove the clips on the slave, allow it to fully extend. Angle at a 45° or so, line facing up. Fill with fluid, wait 10 minutes for air bubbles, then top back off.

Now without spilling, trip on all the tools you have laid around the truck as you crawl under, attach line. Pinch fingers, hit your head 3 times and cuss once, this is important, you cuss twice and you are starting over from scratch.

Once you get the line fully installed, suck all the fluid from the master. Carefully install the clips to hold the slave in retracted position, and it will reverse push fluid into the master, working out a majority if not all air through the lines and into the reservoir. Retract the slave slowly, or you will dump fluid directly into your eyes. Install slave cylinder, release the clips, top off fluid and admire the non functional but bled cylinder.

Done it so many times now I can do it with my eyes closed and one hand ties behind my back, and for some reason it is easier laying in dirt then a clean driveway.

Okay.
Sometimes you just have to drive it and let all the bubbles shake out.

I understand this isn't so easy with a bucket truck.
But I have given this advice to many people so frustrated they want to set their hair on fire (including Gary) and I've never had anyone come back saying it didn't recover itself within a mile or two.

I have tried to drive it. I have gotten quite good at driving clutch less to the point the only time you would notice is when it dies at a red light and I start it back up in gear. My drive to the mechanic that screwed the pressure plate was a 15 mile trip through rush hour, no improvement.

I even saw another post of yours about driving down a bumpy road. There's a lonely old cemetery a few miles from my house down a long, steep gravel road, rutted out with a 5 mph speed limit. I blasted down it at 20 mph hitting my head on the roof after day 2 two of bleeding it before giving up and heading to the mechanic shop.

Before the shop broke the clutch fork, I ran two full tanks of gas on "test drives".

Okay.
At this point we're going to have to consider the clutch fork or mushroom pivot as the last components untouched.

I don't know how or if I can help, but I'm ready to do whatever I can.  

Yikes!  That's quite a story.  

I think you are onto something about the slave size.  At least it makes sense to me.

Speaking of the slave, I think the ZF5 comes in two versions.  If I remember correctly the small-block version is the one with the concentric slave, but the big-block has the external slave.  So when I went from T19 to ZF5 I just used the existing slave.

Harrowing experience in the Pacific Northwet!

I'm not sure if this one has a smaller piston.
It seems to work fine, and it's much easier for me with an actual bleeder.

I screwed around with these slave cylinders quite a bit on three different trucks, and one thing I can confirm is that the F150 slaves are all the same size. They may vary a bit in how they bolt to the firewall, or if they come with a specific pushrod or not, but bore size is all the same. I know that is no help with an F350 issue...but thought I'd mention it regardless.

As for bleeding, at least with the concentric slaves, I used a homemade vacuum bleeder, and then once it was done it was done. It did get better with a little driving, but not long...within the same day the pedal was as good as it ever. I did run a lot of fluid through the system though...I just kept pumping the pedal and kept topping up the master. Probably between a 1/3 and a half a quart. That seemed to work for me at least.

It’s probably completely irrelevant and useless, but here is a picture of Big Brother’s clutch slave cylinder.
F-350, 351W, T18.


I know… Held in place with tie-wraps, cannot find a good clip.

This guy shows how he bleeds the slave cylinder.
Interesting.

So "big brother" uses a different (but similar) setup. You have the clips like the f-150 with the metal bracket that bolts to the bell housing,books identical to the video you posted.

Mine is retained only by a clip, no bolts or bracket, other then the metal clip.

Couple updates, rough eyeball measurements (can't fit the caliper without disassembly and decided I wanted to leave them still assembled) the two I have already replaced (original when I purchased the truck and first one I replaced) seem to be the 1.125" bore.

I think the next step is to source a 1" or .750 slave from rock auto and see if they are actually different, or if it's a typo/ bad information.

The exedy slave cylinder with the bleed nipple does not seem to be manufactured any longer. I cannot find an in stock listing for it, one Chinese website has a listing for $59, but it is a different part number and a "lead time 2-3 weeks"

Another though I just had,

If the master cylinder is .880 bore, and the slave is 1.25" bore, that would mean that the slave would require 125% more fluid, assuming the same length stroke

Basically, we know the master is as long as the threaded rod or shorter, and we know the slave is as long as the pushrod that goes from slave to clutch fork, minus what is proud of the slave cylinder.

So, theoretically, the master would require 125% more travel stroke to completely extend the slave.

As much as I hate measurements and maths, I think I need to start measuring the fully compressed and fully relaxed master and slave cylinders. I can then compare the ratio, and if it doesn't add up to 100%, you would never get full clutch fork actuation....

Why oh why did you cut the retaining strap?


The slave end of the throwout arm only has to move 3/4 at most to fully dose gage the clutch

ArdWrknTrk wrote

Why oh why did you cut the retaining strap?

Jim, I didn’t.  As far as I can remember, Big Bro was as is.
Maybe when my wife’s father was the owner?

You are teaching me that this strap is supposed to stay there, complete.
Listening at the guy’s video, I said to myself «hmm, ok, these little plastic chips were part of a strap in the past…  maybe just there for the installation process.»

So, I understand that this plastic strap is supposed to stay in place?

I am pretty sure it is mainly just to make installation easier, then I think the cup is so you don't have metal on metal squeeking.

I'm one of those people that think ahead.
I can guarantee that you are going to have a hell of a time getting it back together if there comes a day you want to R&R your existing slave (to install the proper clip on it, perhaps?)
It's simple enough to push the throwout arm forward, and slip the little tabs out of the notches in the frame.
It's plastic, and they will hang out forever, without causing any problems., but remain, for you to use them to hold the spring loaded piston in the slave come your next clutch change.
Yes, I do believe the instructions tell to just step on the clutch and break the straps.
I'm logical, and my sense of how things fit together makes me acutely aware of why it comes that way to begin with and the struggle id have if I'd actually followed the instructions

You are technically correct . The best kind* of correct....

Ok thanks, now it’s clear for me!

Bumping this up.

I lucked out on a local gig, they had me use their truck for a month or two, so mine ended up on the back burner. Unfortunately I seem to have run them out of work for now, so I want to get my truck back up and going for another Oregon adventure.

I never did get the hydraulics to operate properly, I have tried every bleeding procedure I could find, but I am going to go through and order the smaller bore slave cylinder.

My clutch fork breaking seems to be a deal breaker, it is a 83-86 6.9 and 85-86 460 "over 8500gvwr" t-19 only part apparently. I have been unable to source one, made a post on the wanted section.

If I can't get one, I can pull a bellhousing from a t-18 and run the setup like big brother has pictured, I just don't want to spend $250 on a bellhousing or spend a full day on my back at a u-pull it yard and run a different setup over a discontinued clutch fork.

So if anyone has a t-19 clutch fork laying around, please let me know.