While using my '89 F150 w/ 4.9L and 5 sp. overdrive manual tranny, a friend of mine experienced engine revving and a slack clutch pedal. After pulling over, he couldn't move the truck. The wrecker driver opined that it was the slave cylinder (didn't make sense to me though). Upon the driver's recommendation, my friend had it towed to a local "mechanic's" place of business, in a small town 60 miles from where I live. My friend is in his 80's and very talkative. The "mechanic" agreed with the wrecker driver's assessment, apparently, and (claims that he) changed the clutch, pressure plate, throwout bearing, pilot bearing, and slave cylinder to the tune of $520.00. After supposedly completing this work, the shop owner called my friend to tell him he did this work, but the truck was still broken, apparently the transmission. (my first thought when my friend described what happened) I talked to the guy and he couldn't explain to my satisfaction how a faulty slave cylinder could cause the symptoms described, made excuses as to why no one thought to check the transmission before re-installing it, and finally ended with " I just did what I was told." He also said that the transmission makes "crunching/popping" noises now. Neither I nor my friend actually told him to do the work, and absolutely did not sign a work order or repair authorization. I hate to get lawyers involved over this, but can't see any other option. Any suggestions? (Particularly regarding the slave cylinder diagnosis)? Thanks!

 

The difficulty here is that there are two problems, which may or may not be related

1) The slack clutch pedal
2) The truck won't move while in gear

These two things normally don't happen together.

If the clutch pedal sinks to the floor with little resistance, the likely causes are, in the following order:

1) Low on fluid
2) Master cylinder seals/valves leak
3) Slave cylinder seals leak
4) The hydraulic line leaks
5) Some sort of massive carnage inside the clutch
6) The slave cylinder piston is stuck in its bore, holding the clutch disengaged

The usual consequence of a slack clutch pedal, at least when it is due to #1 through #4, is that the clutch cannot be disengaged. Without the ability to disconnect the engine from the trans, it is very difficult or impossible to shift. But there should be a solid connection through the driveline, and it is usually possible to start in gear, and even to shift if you are really good at blipping the throttle and matching RPMs.

The pressure plate springs have enough return force as to make #6 highly unlikely. But it is, I suppose, possible. The mechanic should have done some basic troubleshooting before coming to this unlikely diagnosis.

The clutch assembly is a normal wear item, and unless it is
practically brand new, there is always some justification for replacing it, and you get some value out of a new clutch, even if it wasn't the most overt problem. The expensive parts of a clutch job are labor, the pressure plate, and the clutch disk. The bearings are so cheap they are normally automatically replaced.

"Truck won't move" could be due to a very badly worn clutch disk or a pressure plate with broken springs. But usually there is plenty of warning that the clutch is wearing out -- slippage on shifting, rough engagement.

A reasonable shop would be able to give you your old parts back and/or show receipts for the new parts. Especially in this circumstance where there is no signed work order.

You might ask your friend if he had any trouble shifting the trans prior to the "won't move" event. Is it possible that he tried to force the shifter with the clutch engaged, (perhaps due to one of items 1 through 4) and damaged something in trans in the process?

 

Thanks for the info! I had pretty much the same conclusions, though without your obvious expertise. I have a fair understanding of how the clutch/transmission deal works, but no experience with a concentric slave cylinder. The tow truck driver and "mechanic" told my friend that it's a "common occurance" that the slave cylinder goes out, disengaging the clutch in the process..."everybody knows it". Sounded like "BS" to me, and I still believe it's "BS". The tranny had been whining in first through third for quite some time, along with noise in neutral at idle with the clutch engaged but not when the clutch was disengaged, so I expected trouble eventually. I believe my mistake in this instance was in allowing myself to not follow my own instincts and trusting the "experts" to do what's right. It still angers me though.