671 Detroit Clutch problem

[John T]

My 81 year old buddy has a 60’s model 671 Detroit Diesel (Bus RV conversion) with a 4104 4 speed tranny and he can NOT get the new clutch to release properly so the gears can be shifted even when setting still and clutched to put it in gear, the tranny is still turning and the gears have to grind grind grind……..

He installed a new clutch disk,,,,,,,,pressure plate,,,,,,,,,throw out bearing,,,,,,,,,had the flywheel machined smooth. We have adjusted the 6 adjustable fingers (that mate to throw out bearing when clutch is depressed) every which way but loose and adjusted the clutch pedal linkage every way possible in and out tight and loose all to no avail. Currently the fingers are adjusted like ¼ inch away from throw out bearing (i.e. it ONLY turns when clutch is depressed) and when he depresses the clutch pedal to floor the throw out comes forward and pushes the fingers about ¼ inch or more and the springs compress and in theory the clutch disk should be free and NOT turn the tranny so he can shift but Nooooooooooooooooo the gears still grind grind grind SOOOOOOOOOOO we keep adjusting/tightening the clutch rod to pedal linkage to get more forward throw out travel to push fingers deeper and she grinds less butttttttttttttttt then when the pedal is released the fingers are too close to the throw out and it spins constantly (only should when clutch is depressed)……… If we adjusted the fingers farther away from throw out (to stop its turning when pedal released) that wouldn’t help cuz then we just have to adjust/make the linkage move further to push the fingers deeper so the springs compress to release the clutch, i.e. it don’t accomplish anything it seems grrrrrrrrrrrrrrr

Like I said we have adjusted the 6 fingers per the book and NOT per the book and adjusted the pedal rod slack tight n loose everywhere AND SHE WILL NOT RELEASE so the gears can be shifted REGARDLESS WHERE WE SET EITHER ADJUSTMENT

Its drivin me to drink as I don’t have enough hair to pull out. Anyone experienced with Detroit 671 clutches that can shed light on why it don’t release so the gears stop turning and grinddddddddddddddd

Ol John T NOT a clutch kinda guy
 

[rustyfarmall]

Did you inspect the pilot bearing?
 

[John T]

Thanks Rusty NO HE DID NOT I guess if its froze up that could make the tranny shaft keep turning even with a proper working clutch right?????????????

John T
 

[Repair]

Is the clutch in there wright or did it get put in backwards?
 

[Billy ky]

try putting a thin flat washer between pressure plate and flywheel under each bolt..it will move the pressure plate out just a little and sometimes it's enough...i've done that a few times and it worked good on clutches that would not release otherwise...
 

[ericlb]

does the bus have a clutch brake like big trucks do? if so is it new orit been adjusted?
 

[Jon Hagen]

Name: Jon Hagen (Reserved Name)
E-Mail:
Subject: Re: 671 Detroit Clutch problem
In Reply to: Re: 671 Detroit Clutch problem posted by Billy Ky on September 28, 2009 at 19:57:21:
Body of Message:

Two problems causing no clutch release on 6-71 that I have seen ,
1 wrong disc for the flywheel or pressure plate, ( if the splined hub is too large diameter or too long so it rubs on the flywheel or prerssure plate, it will cause a no release condition.)

2 If the trans was plugged into the clutch disc and allowed to sag before piloting into the bellhousing, the disc may have been bent so the disc still contacts the released pressure plate and flywheel. One contact point on the flywheel side and another 180 degrees opposite on the pressure plate.
 

[russ springer]

check the splines on the transmission for wear if they are worn the clutch plate will hang up.you did not say what type of clutch single plate or double.
 

[John T PS]

Heres a copy of my update, disk okay, not warped, correct nice fit n smooth spline and hub, on right direction, good pilot and shaft fit now, see below HOW MUCH TRAVEL SHOULD IT HAVE AFTER THROW OUT CONTACTS FINGERS ?????????? WE HAVE 1/2 INCH DONT SEEM ENOUGH MAYBE????

Wellllllllll I was holding off until I could finally report success but Nooooooooooooo

We pulled the tranny and the clutch n pressure plate Wednesday to inspect the pilot bearing,,,,,,,pilot was like perfect butttttttttttt I discovered the end nose on the tranny input shaft was worn badddddddddddd to where when the end went inside the pilot there was a ton of clearance i.e. it was just hanging/floating sooooooooo he had another shaft and the pilot fit into it tightly like a glove so we reinstalled everything and the shaft fits tight n right into a good smooth pilot bearing now.

New clutch disk slides sweet n smooth n correctly on the input shaft (no burrs or hanging),,,,,,,,,throw out and pressure plate all new and flywheel turned down,,,,,,,the 6 adjustable fingers on pressure plate set pretty even and to within 1/8 of throw out when clutch is at rest THOUGHT FOR SURE THE REPAIRED SHAFT TO PILOT WOULD FIX IT BUT NOOOOOOOOOOOOOOOOOOOOOO still grinds the gears

SOOOOOOO what we think now is the 50 years of wear (1960 4104 Bus) in the clutch linkage and cross directional assembly isnt giving us enough travel where the throw out depresses the fingers. Once the fingers contact the throw out and clutch poedal is full depressed (YES we already adjusted slack as tight as can so fingers arent against throw out) THERES ONLY LIKE 1/2 AT THE MOST OF TRAVEL...... We believe if pressing the pedal yielded 1/4 more inch of throw out pushing fingers deeper (i.e. more separation of plate to flywheel) she will release i.e. not still spin tranny. We have welded a bushing on the big cluth lever arm down lower closer to bell housing to yield more arm tarvel from rod being pulled but that makes pedal reallyyyyyyyy had to push down

Tomorrow we plan to remove the rear floor panel to get to where the clutch rod from up front goes to the cross directional assembly n inspet for wear n slop and interference CUZ WE THINK WE NEED 1/4 MORE OF PUSHING FINGERS SO CLUTCH FINALLY RELEASES

Any ideas on how much travel is needed against fingers so clutch releases?? Theres only like 1/2 inch travel now after throw out tightens against the fingers and I think we need at least 3/4 inch. We will also try it by tightening more slack even to the point the throw out always spins (is full agiant fingers) but at least we can see if pushed far enough it will finally release maybe???

Its a single disc push type non braking clutch on Spicer 4 speed tranny behind a 671 Detroit on a 4104 Bus

Thanks yall

John T (Who invenetd clutches anyway grrrr)
 

[michael a. lee]

with all problems you must start at the beginning. make sure all the linkage to the clutch is in good condition. you are only moving the fingers 1/4 inch, might not be enough. a worn pin and clevis or worn bushings can reduce travel. if it utilizes a cable it could be stetched. it is not a 671 detroit clutch. it is either a single disk push type clutch, a double disk pull type clutch. with the double disk which i doubt it is you also have drive lugs that need to be aligned. generally new pressure plates do not need the fingers adjusted.