Clutch time

[SRR]

I have a 1988 F-350 DRW 7.3 IDI ZF 5 speed that I rarely use. Basically a farm truck that rarely ever goes 500 miles a year. Only two 50 mile trips to town so far this year. It's a good truck with a good engine. I just fired it off for the first time since March and it started immediately, so quickly it scared me :-)

Anyway, the last few years it's been increasingly more difficult to get it in reverse. For quite a while I could put in first then quickly shift into reverse. Now it just won't go into reverse unless I put it in and crank it up that way. Over this time since the difficulty began, the engine has spun up under power maybe ten times if I give it too much power under load or if running the cruise control. Obviously the clutch is going out. I can't think of anything else it could be. The pedal also sucks down to the floor sometimes and I can't feather the clutch to slow it down when going in reverse. The ability of the clutch to disengage goes away if I do that.

So... I'm not sure if this thing has a dual mass flywheel or not. Is there any way for the mechanically challenged to verify flywheel type without taking it apart?

Say it is a DMF, with the very intermittent usage this truck gets, what are the odds of success if I just have the clutch assembly replaced and leave the flywheel as is? There is no symptomatic clattering to indicate a bad flywheel when in operation or when shutting down the engine.

I know the smart thing to do is go for the luk conversion but if I can avoid the $600 for that kit, I would rather just do the clutch. Any reasonable chances of success in this case?

Thanks,
Don

[Mr_Roboto]

I believe something is sticking inside the bellhousing. Either the clutch splines on the input shaft, or the throwout bearing on the (transmission doo-dad). The result is that your clutch is staying partially engaged (and disengaged) all the time. I had something similar happen on an old 85 F350 from rust as the inspection plate was missing.

I've seen similar problems posted here before, hopefully someone can post the fix.

[BuilderBob]

Sounds like you have 2 issue, maybe a clutch issue, but for sure you have a bad linkage.
This involves the linkage, the clutch master & slave cylinder.
Likely it is the master & slave cylinder. Get on your back under the steering column and follow the linkage and look for worn out parts.

Most of the advertiser for clutch/pressure plate on this site will sell you the parts needed for replacement of the master/slave, under $100.

Examine the clutch by removing the inspection cover, have it done by a trusted clutch u-joint shop, get an opinion.

With labor, LUK (clutch/PP/flywheel)& master/slave, = $1400

[SRR]

That's wild Roboto but it makes more sense than the clutch being worn out. This truck does some weird things sometimes. When idling in neutral it will sometimes pull the clutch pedal to the floor requiring a kick to get it back up. Other times it will do the same thing when idling out to the highway in second gear. Gotta kick the pedal to get it back up again.

BuilderBob, I've suspected the hydraulics and have checked the fluid. I've also looked over the mechanical linkage parts under the dash but couldn't see anything wrong. I'll have a closer look at all of it tomorrow.

Thanks,
Don

[Greg77]

I suspect under your limited usage your slave cylinder is starting to leak. They are very touchy anyway. There is also a bushing in the linkage at the rod end of the master cylinder. It is plastic and if it gets worn it will make your linkage just long enough to make it hard to get into gear. You said the clutch is slipping in gear. This will have nothing to do with the slave or master cylinder. Once it is in gear it's in gear. If your flywheel is not rattling when it idles or shakes when you shut it off chances are it's good yet. You can put a new clutch and pressure plate complete kit from Luk or whomever in for a couple of hundred dollars. If you put in a new bushing ($10.00) and slave cylinder (($65.00) and new clutch and pressure plate ($200.00) you should be good to go. You can do a more complete check on the dual mass when you get it out. As long as the springs are good, (not worn in spots) you can tell when you look at it,and the surface of the flywheel seems good for your usage it will last a long time.

Greg

[SRR]

Good Mornin" Y'all. I have some updated and corrected information.

After doing some more looking, I have multiple problems. Since the engine will sometimes spin up if I nail the throttle at cruise, the clutch has to be slipping but that's not the most immediate of issues. I want to start fixing from the top.

First thing I notice is I have nearly 2½" of free play in the pedal before I hit any resistance. The little black bushing at the connection of the linkage and the master cylinder rod is shot but that wouldn't account for that much free play. Would this amount of free play be caused by other linkage components under the dash or a faulty master cylinder? None of my books say anything about working on the mechanical linkage assembly.

The second thing has to be hydraulic.

The master is still full to the step so I can't have a leak but here's what it does. When I push the pedal to take up the free play, I can hold a steady but relatively light pressure on the pedal with my thumb and the pedal will slowly sink to the floor. At any point in the pedal fall I can release pressure and the pedal will stick. The only way to get it back up is manually pull it back up.

In retrospect, what I wrote above "When idling in neutral it will sometimes pull the clutch pedal to the floor requiring a kick to get it back up", isn't true. I think that symptom always required me to catch the pedal edge with my foot and pull it back up.

When I push the pedal with force as I would when disengaging the clutch, the resistance feels normal and the pedal returns to the stop upon release. If, however, I hold the pedal down, it sticks to the floor quickly. At four seconds I can feel it giving up it's last bit of resistance and it sticks. If I hold it a lesser period of time, it comes back up partially.

Is this most likely air in the system or a bad master or a bad slave or all of the above?

Thanks again,
Don

[Mr_Roboto]

It still sounds to me as if the clutch disk or throwout bearing is sticking.

The clutch disk splines slide on the input shaft splines as the clutch engages and disengages.

Also the throwout bearing slides on the sleeve outside of the input shaft. I would suggest taking off the inspection cover, and spraying some white grease where the throwout bearing slides.

The clutch master, slave and line are sold by Ford as a 1 piece unit and there is little sense in replacing it in pieces.

Also check to see if you are getting firewall flex / bending near the clutch master cylinder.

[SRR]

Thanks Roboto. I'll be having a look at the clutch iself when I pull it into the barn. Is any lithium grease okay to use?

I don't see any firewall flex and all of the free play in the pedal appears to be in the master cylinder itself. I called Ford and they want $341 for the system but they have to order in the master. O'Reilly has the master and slave for $83.

How much free play should a clutch pedal have? Am I barking up the wrong tree thinking the hydraulic system is shot just because I have 2½"?

Don

[Mr_Roboto]

Any light grease is fine, I just recommended white grease because it comes in the spray cans.

Get some lube on that sucker and work the clutch, you may loose some of that free play if I'm right about the problem.

[SRR]

Dang, I didn't know thaere was such a thing as grease in spray cans. I'll open it up in the AM and see if grease will do the trick.

I got a new master and slave but really, the old ones probably can't be be bad if it's never leaked down and it's still full of fluid. Weird truck.

Don

[Greg77]

There isn't rally any free play on the dual mass clutches, maybe !/2 inch. Your master cylinder may be leaking past the orings on the plunger internally which you wouldn't see. There also is no other linkage on the clutch system it is all hydraulic except for the clutch fork that move the throwout bearing in and out.

[Garbage_Mechanic]

Roboto has some good points but secondary to the real problem. If the pedal sinks under constant pressure, the hydraulic system is bypassing. Also, this system is designed to have as close to ZERO free play at the pedal as possible. This is backwards to all the years prior to 83, where if you didn't have free play you were in trouble. Also the clutch hyd system is no different than brakes, what would you think if your brake pedal sank to the floor with your foot sitting on it. I think you need to be sure the hydraulics are good and there is no more than 1/32 inch free play in the master cylinder pushrod, and that the cluth pedal shaft bushings don't have excess play (read as none).
As to lubing things up....while you have the slave cylinder off slip the fork out of the bellhousing, comes right out, just pull and wiggle. While its out you can use a spray can of penatrating lube to lube the slider where the throwout bearing slides. Its common for this to get gummy as Roboto said, but you are dealing with dried up dirt and grease mix. Also lube all of the pivot points on the fork.

After all of this, if it still doesn't release properly, you will still have to pull the clutch. I'm going through the exact thing right now on my ranch truck. The release problem on it was dirt and worn off clutch material between the diaphragm and cover. I couldn't justify the $600 smfw either although I would love the decreased pedal pressure etc. Good luck, let us know how it goes!

[SRR]

Hey Greg,

It's tough being a mechanical dummy. Duh, just because it isn't leaking fluid doesn't mean it's pressurizing the line and the operating the slave. That would certainly explain why I can slowly push the clutch to the floor with a fingertip. Seems like it would also explain the free play if fluid is trapped in the cylinder on the back side of the plunger. Last night when you said my stuff may be starting to leak, I thought you meant leaking to the outside.

Thanks garbage mechanic. Yes, all the free play is definitely in the master pushrod.

Don

[Mr_Roboto]

Yep, master cylinders will leak internally around the seals when they get worn. And it doesn't help with a truck like yours that sits a lot, since the rubber hardens up from not being used.

I used to run an electric forklift, the brake pedal was good for about 10 seconds before it hit the floor. Same thing, leaking internally. You really had to know when you were going to stop, there weren't any second chances on that thing.

Yep, white lithium grease in a can. It's WONDERFUL stuff, it's what's used to lube car door hinges, I also use it to lube my garage door tracks and anything that slides on my wrecker. You put the little plastic straw on the can and the stuff will shoot a good foot or more.

[SRR]

I can't find a way to post pictures for part identification but I have a UFO.

Okay, I'm changing out the clutch master cylinder and I find this thing tucked away up in the insulation in the firewall area inside the cab. It appears to be a brace for the firewall/master cylinder connection since it fits on the uninstalled master very nicely. Problem is, it won't even come close to fitting in actual usage because the saddle or whatever you call the thingy for the steering column penetration is all in the way. Bolts on the master aren't long enough to even reach the holes in this thing.

Is there normally a kinda strange looking steel brace inside the firewall? It maybe looks like a muffler clamp a dude on LSD might fabricate.

Don