Sudden Extra Clutch Pedal Play ?

[Robert Crandall]

My clutch pedal suddenly went from 1 to 2 inches of play to near half its travel distance of play.

My truck is a 1978 C20, 292, granny gear 4-spd. I bought it new. This has happened twice before. Reviewing my records shows it happened at 163k miles and again at 233k miles. In both cases I replaced the clutch to fix it. The speedometer broke at 365k miles, so I estimate that I now have around 380k miles, and the same thing just happened again. It takes me 2 evenings after work to get the clutch out and 2 more to get it back in. I don't want to do it again.

Does anyone know what happens to cause this? In all three occurrences, the clutch works fine, but I have to stretch and get the pedal to the floor to use it. I adjusted the linkage a little, but the play is not free, open play.

Thanks.

[mongocanfly]

what brand/style clutch are you using?

[kipps]

Sounds to me like a throwout bearing failure. Basically, the throwout bearing self-destructs, moving the point-of-engagement down below the floorboards.

I have no experience with this in a truck, but I've seen it in a tractor. And since everyone likes bedtime stories ---

I was at another farm about a mile and a half away feeding hay at 10 o-clock at night(Emergency situation -- long story). The clutch suddenly got to where it wouldn't disengage, so adjusted the free-play. Worked for 3 more clutch-presses, then needed adjustment again. Ran out of adjustment, and finally drove it home without a clutch. That was a bit of a harrowing ride, with nearly no lights, and no clutch. Just used the synchros in the tranny to get it rolling, then rev-matched from 1st gear on up. Opened the inspection cover on the clutch housing, and it was full of shiny curly-q's of metal from the destroyed throwout bearing. If you've ever seen trimmings from a metal lathe, these looked very similar, since the exact same thing was taking place.

While this throwout bearing turned into steel "excelsior," it's possible that yours could have collapsed in a more discrete fashion. When you get it apart, compare the old TO bearing with the new one. I'm almost sure you'll see the failure.

[dmack91]

Could also be a broken diaphragm spring in the pressure plate. Sounds like you will be replacing all of the clutch components. Could be worse.

[Peanutbutter]

Was this a diaphram or borg and Beck pressure plate? Did you replace the bearing each time. No matter how good you think the bearing is throw it and put in a new quality bearing.

[kwmech]

I had the same thing happen to me when I had my 78 Wrecker. Turns out I had to rebuild part of the linkage, mostly where the pedal swings under the dash, Pulled out the long bolt and changed the bushings and lubed it all up in both the clutch pedal and the brake pedal. Welded up the oblonged hole in in the steel plate (and redrilled), that connects to the rod that goes through the firewall. Generally went through all the linkage and tightened it all up. Worked like brand new when I was done

[Robert Crandall]

Thank you for all of your advice. The brand of clutch is whatever my FLAPS had in stock at the time. It is the diaphragm type. Of course, anytime I am into any clutch, I replace the throwout bearing. I do agree that it could be either the diaphragm spring or the throwout bearing. On both of the earlier replacements, of pressure plate, disc and bearing, there showed negligible wear on the friction surfaces. Something just broke. I had to fix it quickly the first two times because the truck was my daily driver. Now it is retired and registered as an antique. I drive it to work once a week and when I need to use a truck, so I do not have to hurry with the fix. I like driving my relics a lot more than I like working on them, but I will fix it.

I bought a new linkage to replace the oblong hole some time ago. It is not bad now, so I will leave that as is for now.

I like the story in post #3. I spent some time working in England. While there I bought an old right hand drive Volvo. The clutch operation and the master cylinder were on the left side, just as for left hand drive models. A bar linkage for the master cylinder went over the engine to the 'other side' pedal. A very long cable went around the front of the engine to connect the clutch to its 'other side' pedal. That cable broke one time about 50 miles from home. Lucky, I was in a rural area, and England uses 'round abouts' more than stop signs, so I rarely had to stop. I had to drive as described above - push then jump in for 1st then rev match the other gears. It worked, although my rev matching was not always the best.

[tucsonjwt]

A long shot, but I would crawl under the truck and check the adjustment on the clutch cable. I have adjusted the nut until I had about 1" of exposed thread and that made a big improvement in the clutch engagement.

[Robert Crandall]

Thanks. I did diddle with the adjustment a little. I drove it to work today, and the clutch seems to work fine now. If I am lucky, then it will last. My adjustment is a rod. Something seemingly in the area of the clutch has been making a ringing sound when I turn the engine off for some time now. Maybe the two things are related.

[cadillac_al]

I was thinking your clutch disc gave out because it sounds similar to how clutches fail in big trucks. When a chunk of clutch disc falls out you will lose your pedal immediately but it will still work for a few more miles in a big truck. In a pickup it may go a couple weeks. Then you mentioned the ringing which makes me more sure your clutch disc is falling apart. I would start preparing for a new clutch in the near future..

[Robert Crandall]

Yes. Mental preparation is in progress. I do appreciate that I am given warning rather than being suddenly stranded somewhere. Spending money and doing work will follow, but not quickly.