Clutch pedal goes to floor

[MSeriesRebuild]

Concerning the possibility of an incorreect collar; I guess anything is a possibility at this point.

I'm thinking if we had gotten a couple of pictures of the assembly with the bell housing bottom cover removed, this deal very likely could have been already settled.

[Cal_Gary]

I understand your responses, Charles-guess I subbed "forks" for "fingers' inadvertently in my mind. As an FYI though, while my pressure plate's fingers are adjustible, I've never had to do this-sorry for the confusion, folks!
Gary

[m37jarhead]

For now it looks like the problem is with the old pressure plate. For some reason the fingers just recede way to much
towards the engine when the pressure plated is bolted on. This results in excessive throw out bearing travel.
This does not happen when another, used pressure plate is installed.
Also contributing to the problem may be that my new disk is a bit thicker than the new disks that Charles has.

A new pressure plate has been ordered. Hopefully this should solve the problem.
Will keep you all posted on the results of the new pressure plate once it's installed.
Thanks for contributing all of the tips and advice. It WAS driving me crazy. (crazier?)
JB

[DJ]

Been following the saga here,when the pressure plate idea came up a thought came to me. A guy on the M715 forum had the same situation,only he had a new pressure plate he bought on Ebay. He determined that it was not working,ordered a new pressure plate from Memphis equipment,and his problem was solved. Good chance a quality new pressure plate will solve your dilema.

Good Luck! DJ

[Kaegi]

maybe it just had the wrong pressure plate installed at some point. still doesn't make sense that is would be that far off just by replacing the disk though. did you ever drive the truck with the old clutch?

[m37jarhead]

Yes I had driven the truck before engine problems shut it down. The transmission and clutch were working fine. No trouble shifting gears.
All seemed normal to me at the time.
The engine was rebuilt and a new throw out bearing and disk were installed. The thicker new disk brought the pressure plate problem to
a head. As the bolts on the pressure plate were tightened, the "fingers" on the pressure plate were forced to relax more and recede towards
the engine. This caused the excessive travel on the throw out bearing. There never was a problem with linkage or pedal adjustment. Also
new bushings had been installed at both ends of the forked rod in the bell housing eliminating any excessive play there.

At the suggestion of HB from Buckeye,AZ. (a frequent contributor to g41 forums) I set up a "bench test" with other components that I
had on the shelf. A used flywheel and pressure plate on the bench were used to test the new disc. Eureka! The fingers on the extra
pressure plate DID NOT recede the same distance as the fingers on the pressure that I had been trying to re-enstall.

With this information, Charles at M-Series Rebuild confirmed that the pressure plate was bad and needed to be replaced. His advice is
to always replace the disk and pressure plate at the same time. Yep.... I shoulda', woulda', coulda' but didn't. The pressure plate
"looked" good and was operating normally before disassembly. Trying to save a few bucks caused the nightmare..... never again.

A new pressure plate is being shipped. I'll bring you all up to speed once all parts have been installed. Keep yur fingers crossed for me.
JB, Gilbert,AZ.

[Kaegi]

interesting, thanks for explaining. seems like the plate levers were set at the wrong height. or maybe it has the wrong arms/levers installed. I bought a rebuilt pressure palte once and 2 or 3 of the springs were the wrong stiffness. took pulling the tanny 3 times to figure out why everything was binding when you push the pedal in. clutch rebuilder could not figure it out. I ended up testing the force to push each lever and one was WAAAY harder to push than the others. that one was a head ache!

[MSeriesRebuild]

Jerry and I had a lengthy phone converstion concerning this the other day. Bear in mind, I still have not seen the issue, so nothing is absolute because of that factor; however based on our discussion, I think it goes like this.

I don't think his plate assy is bad in the sense of not functioning correctly; I think it is a plate assy that has gotten into an application it was not intended for. From what I can gather it was most likely set up to be used on a stepped flywheel. When he put it back in place on a flat face flywheel with a new disc that is also thicker than the original new spec disc used on the M37; all these issues in conjunction with each other was enough to put it out of the range of functioning properly. Apparently it was working right on the edge of the spectrum before he replaced the disc; the thicker than original new disc just took it over the top.

Issues like this are more common than you think when dealing with clutch rebuilders. Many will use common in stock parts to rebuild rather than sourcing not so common exact spec replacement components. They are thinking a disc lining that is .100" thicker than spec won't matter because there will be significant adjustment to overcome that. In many cases that is correct, but in a few that are on the edge of specs already, that isn't so at all. They do the same thing with pressure plate assy springs as someone else mentioned. We've had some in which some of the springs were left out of the assembly. Stiffer springs were used with every other spring or every 3rd spring left out for instance. This will work for a while, no real difference in pedal pressure will be noticed; but when you factor in exact plate pressure like it should be all the way around the circumference of the plate / disc assy, it ain't happening. It will cause uneven disc lining wear, and will result at some point in erratic clutch engagement, many times the uneven wear will lead to rivets cutting into the flywheel and pressure plate surfaces, etc. It is a must that one pay close attention to what any rebuilder does these days; some will literally tell you anything. Before you know it, you own a deed for London Bridge, and trouble down the road. Many vendors who have stuff rebuilt for resale do not pay attention to what they are getting from rebuilders. Some don't have a clue and have never actually worked on trucks with providing correct builds in mind. Seek out reputable suppliers when you source parts, there are some out there who simply are not reputable and will tell you anything to make a sale.

[m37jarhead]

Sorry to say that's it been almost a monthe since I received the new pressure plate. Did a "bench test" with it before installing.
The fingers on the new p.p. stand quite a bit more proud than the old unit once it's bolted to the fly wheel. Good news there.

Then got side tracked by r & r'ing the clutch and brake pedal shaft and bushings as well. Of course, all those parts and pieces
had to be degreased, sand blasted, primered and painted. The old shaft was badly worn and required purchasing a new one.
The bushings, as you might expect after 50+ years, were toast. Finished installing the shaft and pedals with new bushings a few days ago.
Also replaced all clevis pins on the linkage with new. Doing those things made a big difference in tightening up all the slop in the
pedals and the linkage.

Planned on re-installing the transmission tomorrow, Sat., but wouldn't you know it, rain is predicted. It's not SUPPOSED to
rain in Arizona.

I'll get to it in the next few days and keep everyone posted on the results.
Tks,
JB

[m37jarhead]

Well, I finally finished installing the new clutch disk, new pressure plate and new throw out bearing.... AND also hung the transmission back on to
the bell housing. Clutch pedal works normally again. Looking up from the bottom of the bell housing, the throw out bearing travel appears to
be normal. So.... it boils down to the fact that the old pressure plate was bad and that caused the problem with the excessive throw out bearing
travel and causing the clutch pedal to go to the floor. Night mare solved.
Thanks to Charles for helping diagnose the problem and to all the others on this post in trying to help solve this mystery. All comments were
REALLY appreciated.

A side note here. If you don't have a clutch "alignment" tool I suggest you get one before re-installing the disk, p.p., throw out bearing and
transmission. Numerous unsuccessful attempts to stab the transmission were made before I borrowed an old transmission input shaft to
align the disk. That did the trick. Using my old 3/4" smooth rod got it close but no cigar.

Thanks again to everyone for their help and suggestions.
JB