Spicer 4 Speed Clutch adjust

[Fredward]

I replaced the clutch in my MCI-5A four years and 20,000 miles ago. I purchased the correct clutch (from C&J bus repair) and adjusted it according to their guidelines. I have not adjusted it since that time. But i do grease the various lube points periodically. Two weeks ago after about 300 miles of driving, in 94 degree weather, I stopped for fuel and the clutch suddenly began dragging. At a stop, the only way to shift from Neutral to First was to put the clutch in; shut off the engine, put it in first and then restart the engine. The clutch still works, it just drags. I turned the adjusting knob about three turns clockwise and the problem went away but then the clutch slipped. Back off the knob a turn and a half and now the clutch drags less but still is difficult to get from Neutral into First. SInce then I've driven another 450 miles back home and it hasn't gotten any worse. I have not taken the time to mess any more with fine tuning the adjustment since arriving home. The air assist cylinder still seems to function normally.

THe manual doesn't really offer much other than to turn the adjusting knob. A visual inspection up into the inspection plate doesn't reveal anything wearing or broken or loose. The linkages all look OK. But it seems very strange that the clutch would go from working perfectly to dragging all in one morning in 300 miles.

Any thoughts or tricks would be welcome. The sudden change is what concerns me most.

Fred

[Len Silva]

Fred,

I don't know about your MCI but on the 4104/4106 there was a whole sequence of adjusting the clutch beginning at the front and working your way back in order to get all the geometry right.

I think you may have problems up front resulting in a short throw at the bell crank.  Two or three turn of the adjusting knob should not make the difference between slipping and dragging.

[Utahclaimjumper]

I would look very hard and long at the "air assist system,, it may not be pulling/pushing the linkage enough to fully release the clutch.>>>Dan

[bevans6]

There is/should be a grease nipple to lube the throw-out bearing - is that still there?  Anyway, I would start by disconnecting the linkage at the top under the floor cut-out to separate the whole pedal linkage from the clutch meccanno set on the gearbox, , and start playing with it to see what is stuck.  Fiddle about and look for what is binding.  Mine had seized heim joints on the aforementioned air assist cylinder, fwiw.

Brian

[gus]

As Len said, on GMCs there are numerous clevises and pins from the pedal to the clutch, a few worn pins and wallowed out clevises multiply into a great big slack in the system. I spent many hours on my 4104 replacing all these things. I found the cross shaft under the driver also lose in its mount.

However, the biggest problem was the bellcrank at the firewall where the clutch rods connect and make a 90* turn to the clutch rods. The arm holes in the bellcrank were completely worn through the bushings into the arm castings.

Even after all this my clutch still dragged. I just learned to live with shutting down the engine to get to first gear, after that I was careful to shift down into first in traffic just before coming to a stop, it takes very little movement to make it easy. This is hard on the clutch leg though if one stops for a long traffic light! When that happens I just shut down to shift. A nuisance but doable.

[Ncbob]

Fred, you might be overlubricating the throwout bearing and getting grease on the clutch plate.

Da Book sez: Note the numbers below the clutch adjustment knob. Turn it clockwise until it is tight (don't try to wring it off) and
back of 8 numbers  ..I use 10.. and forget it.

Hope that helps.

NCbob

[bevans6]

All the clutch adjustment knob does is adjust free play at the throwout bearing.  If the clutch isn't releasing properly, that may not be the problem.

Brian

[Fredward]

Well it sounds like I better look more closely at linkages. Very strange that it just started dragging. It has not acted up at all since i replaced it. I replaced the bushings on the clutch shaft and inspected everything else when the engine was out. Maybe I should look up in front.

[bevans6]

Reading again, you had the engine out and do some work on the clutch.  Did you change the pilot bearing?  A seizing pilot bearing could create a similar symptom to a clutch that isn't fully releasing.  A friction lining that has decided to part ways with it's disc.  A floater plate that is binding up in it's slots.  Broken spring.  Clutch finger adjusting bolts out of adjustment (they do move sometimes I am told).  Try adjusting to one-half to three quarters of a turn from full in on the adjusting wheel.  When you adjust that handle you take out all free play then add some back in.  A full turn gives you the factory amount of free play, a little less will give you less free play but more disengagement on the clutch throw.  Make sure the pedal height adjustment is right, you want the correct height on the pedal so you get full movement.  Is there something stuck under the pedal (lame idea I know).

Just some ideas...  When I was focused on the linkage, I thought dragging clutch meant the clutch wasn't engaging freely (pedal was binding down and not coming back up) and was slipping- I think you mean it isn't disengaging all the way, making for hard shifting.

Brian

[Lee Bradley]

On the downside, a broken pressure plate.

[gus]

Fred,

Even if the clutch is perfect there are so many places for slop in that long linkage. The worst place I found was in the bellcrank but the other forks and pins were pretty worn also.

[luvrbus]

Is that a single disk or double disk clutch ? pull or push type ? button or lining ? I have saw several different type clutches in a 5 and never knew for sure what type they really used with different serial numbers the clutch would change

Me I would check the spring if you have one they were bad about flipping over center 

good luck

[leroy]

I put a rebuilt cluth and preasure in my 4104 .had problems with not releaing
found that the cluth plate was warpted. had it trued up it works fine.
leroy

[pvcces]

And we had the center break out of one of the discs, which gave us the same symptom. We never did figure out why it broke.

If you work at it, you might be able to get the pedal all the way down and see if the discs are loose. That may tell you which way to look for your problem.

Tom Caffrey

[Fredward]

After inspecting linkages I discovered that the pedal itself can be adjusted (kind of what you were saying Brian?) I loosened that clamp and lengthend the pedal travel by about 3/4". That made the difference and then I readjusted the adjusting knob as mentioned elsewhere in this thread. Drove it around yesterday and now the clutch seems to release just fine. I'll look in the book again tonight, but i don't recall seeing anything about how far the clutch pedal should travel. There is a flooring material that was installed at the time of the conversion that inadvertantly prevents the pedal from going all the way to the floor.

This still doesnt' explain why it all of a sudden it started dragging (not fully releasing). What are the downsides of me lengthening the travel of the clutch pedal? Can I make it go too far and screw something else up? Of course I have 40 wt oil in it and the temperatures were high.

When i replaced the clutch, i replaced the throwout bearing and the bushings on the top of the transmission that the clutch shaft rides in. I'm not sure what type of clutch I put in it other than I bought it from C&J bus here in town and they are an MCI shop. I'll check to see what it was they sold me.

Still checking because this doesn't seem like the right answer.