I have a 1987 F250 Xt-cab super-duty 4WD w 6.9-L diesel & 4 on floor & the (multiply-cursed) hydraulic-assist system for the clutch.
I have replaced the slave 4X, & was about to replace the master & slave when I hit big pillow drifts 'blind' coming home during a blow after work last week.
"Big" means they were more than 25 feet long & bumper-deep or deeper. I live alone in the country, I work 2 - 11 p.m., and I was doing 35 mph when I hit any of them, as that was the maximum safe speed. Hit them blind bcs every one was just past the crest of a hill on the back side of the rise. Buried the pickup 3X.. even at 35, 3+ tons of machine doesn't stop quickly.. Put it in 4, backed it out, shovelled when I had to &/or chopped snow w an ice-chopper, since it was packed before I hit it. Getting home was a royal pain..
After the 3rd one, the clutch began to stink & of course I couldn't shift, so crept the last 1/2 mile in 2nd, and moved it the next day about 12 miles (in 2nd).
Obviously, I'm going to replace a clutch that had only about 20,000 miles on it, but my question is, why do these damned things keep going out at all? I've been mechanicking since I was 13; was trained by my uncles, who were all super-picky well-trained people.. I believe it's the system, but is this a problem for this system 'all the time', or have I missed something some way?
I don't know if it's important to solving this, but the clutch was done by a shop that came recommended by people I trust & after I paid the bill the guy who owns said shop told me, "Uh - we noticed when we replaced your clutch that the ring gear has chatter. We didn't turn it because you didn't tell us to." I raised hell about it since this is a mistake high school kids might make when first learning, but should never happen in a shop that claims accreditation for competence; I shouldn't have to tell them how to do their job properly.. Then I turned them in to the state's AG Office of Consumer Protection. Doesn't do anything to them but it makes a record.
I bought the truck Halloween 2003 & except for this hydraulic cylinder thing, it works well for me. Thanks for any help you can give.

 

Well if you mean the flywheel was warped, scored or hot spotted you don't have to ask why it would eventually (at 20k) fail pushing a 4x4 through heavy drifts.

As for "multiply cursed"
There are lots of issues I've dealt with my '87's clutch.

1) Firewall tearing around the clutch M/C
2) Bushing/clip on the pedal shaft bell crank(where it connects to the M/C pushrod)
3) Worn/missing bushings in the pedal support casting.
4) Pushrod updated to longer 'adjustable' one.
But all these things make it hard to disengage, they don't cause slippage.

At least mine doesn't have to deal with the additional torque of a diesel....

 

The flywheel isn't warped so far I know, altho I will check, of course, when I tear the pickup apart. I will check into the linkage thing. There are no extensions in place of OEM-length parts; I checked that, too. There shouldn't be a problem with a diesel engine vs a gas engine or with it being a 4 WD unless Ford under-engineered the system to begin with. Not that that would be a surprise.. Ford gave us the Edsel, after all. They aren't immune to screwing up in favor of building cheaper so they have a bigger profit margin, and we who buy these things pay for it more than once, especially if whoever owned them before us didn't do their homework & maintain them properly. This one wasn't and I've had to all sorts of replacements as a result. The nitty gritty is, when a company builds something as big as this pickup, corner-cutting should not be an option, and the entire world does not run on itty bitty baby trucks that can't do what is needed when it is needed. If I wanted to live in some damned subdivision, I would. I prefer to be part of feeding the world, and that requires large, heavy-duty vehicles, which I don't believe in buying new (and untested). Pilamiyaye / thanks for the answer.