Clutch carnage...how did I do this?? Long!

What are friends for?? How bout they show up and drop the tranny out of your M715 cause they know you can't and it needs to be done!!
Last summer, I was wheeling, going down a steep but short hill in 4 wheel low, first gear. I was rolling at less than a mile an hour using the brakes to keep from going faster. At the point where I had maybe 5-10 feet in front of the truck until I hit bottom and started going back up...due to the bottom of the hill not being of long enough length for the truck to sit flat on...I pushed in the clutch and let the truck roll with no brake. I might have hit 4 or 5 mph max by the time I was going up already, probably less, and as I was slowing on the uphill, I heard a "snap" come from the bellhousing area. It was not a good sound as my impression of the sound was like a pair of vise grips were locked on a bolt hole "ear", on say a bellhousing, was hit by a hammer and broken off...the noise I heard would be of that ear beaking off...not the hammer hit...like thick metal had snapped off. I was able to drive the truck 3-4 miles home...I could not exceed 40 mph due to slippage in the clutch. I had to make 3 stops to get home and take off from the stops...when I got home I pulled in front of the shop and then tried to go into reverse to back in the shop...no gears left...had to push it back in...
Well its been sitting there waiting for me to get to it...was too busy, then injured...anyway...
Kevin and a friend of his came over and pulled the tranny....then took pictures of the mess. I made a page for them with brief descriptions at the link below.
http://www.m715zone.com/jonmisc/clutch_carnage.html
Basically, the pressure plate side of the clutch exploded but the flywheel side looks fine. Most of the clutch debris was found on the engine side of the flywheel, with a coating of powdered or cottonny clutch material everywhere.
Have a clue what exactly happened in there?? The clutch pedal was on the floor when this happened...the clutch was not excessively worn and was adjusted recently...it had less than 10,000 miles on it. The pressure plate and throwout bearing were replaced with the clutch, flywheel had less than 20,000 miles on it at the time and was not resurfaced after a good inspection showed it was in good shape...the original clutch also exploded in the truck but this was due to a couple of reasons that do not have bearing on this 2nd explosion...at least I dont think so...
When I bought the truck it had 14051 miles on it...by the time it had 17000, which it had after about 5 months of me owning it in 1995, I had adjusted the clutch about every 2-3 weeks...since it was wearing at this rapid rate, I figured it had something to do with its age and low miles, etc. I bought all the stuff to change it and was headed to my brothers place to do the job when I entered a small town on the highway, after running at 55-60 mph for about an hour. I slowed to 30 mph in 4th gear and then pushed the clutch pedal in to slow down more. When I did, 1/3 of the clutch material on the pressure plate side of the clutch departed the disk. I stopped at a friends there, was able to coast in, and as I sat at idle there, I kept slowly letting up on the pedal till I heard an abnormal noise, then I pushed it back down...after spending several minutes doing this in neutral, the abnormal noise quit and I was able to drive it 25 miles on the highway after that without incident. Bump_r told me that the problem had to do with the old clutch plate being crushed under pressure for so long over the years and age deterioration, that when I bought it and started putting miles on it quickly, it started making a lot of heat and swelling up due to that...at the point where it failed, it basically failed while I was at speed and had swelled up waiting for me to push the clutch pedal down...when I did, the part that broke away did so because it was only being held in place by the pressure of the pressure plate...if I had pushed the clutch in at 60 instead of slowing to 30 first, it woud have happened then...a very different reason for a clutch to blow I think....
So look over the pics and let me know what you think...I'm still wondering if something else is screwed up besides the obvious clutch plate...did something else fail and cause this?? Am I missing the real cause of the failure?? I just cant see a good disk failing under the conditions it did...I have done that same thing before and never had any problems...what is different here??
Thanks for reading...whew I'm ready to rest after typing all this...took me over 2 hours!!
brute4c

Not much help here Jon but nary a one photo worked for me.

Chris

photos didnt work for mr either
btw, did you get a towbar? the remaining pieces i need should be in this week

Looking at the pic prob...should be fixed soon!??!
I have the adapters but not the towbar...havent really been looking lately...got any leads??
brute4c

Pics are good to go now....thanks for pointing it out!!
brute4c

Jon, I wonder if the disk had faulty material. You said it happened before. Did you get the disk from the same supplier? That is the strangest cotton like debris. It is almost like something caused the lining to soften and explode under use. I have never seen something like that before. I'm afraid I'm not much help. Good pictures though...

I have no ideas either. The only thing I can think of would be your pilot bearing. If it is worn of gone, the super long trans input shaft could be walking around a lot. This could cause your clutch disc to get moved laterally. The only way I can think of to check this, besides looking at the end of the crank, is to measure the shiny area of the flywheel. Then compare that measurement to the diameter the clutch disc is supposed to be. Like I said, I'm reaching for oddball ideas. At least your rear main seal is actually sealling and everything isn't covered in oil.

Appreciate the ideas...I'll have that stuff checked. I have not replaced the pilot bearing so its a possibility.
The disk that was in the truck when I bought it was the stock disk and was 28 years old at the time of failure/replacement. I used a replacement from Napa for a 65 J series/Gladiator truck with a 230 engine and t-98 trans...same size and spline exactly as what came out...should be good material??
The debris is pretty funky...like some kind of cotton...no hardness to it at all...the guy who cleaned out the pieces between the flywheel and block/starter...where most of it ended up, said it was like sticking the screwdriver up into bread dough...and of course it stuck a nice coat to everthing in the bellhousing...everywhere in there...gotta clean the heck out of it!!
brute4c

"Bump_r told me that the problem had to do with the old clutch plate being crushed under pressure for so long over the years and age deterioration, that when I bought it and started putting miles on it quickly, it started making a lot of heat and swelling up due to that...at the point where it failed, it basically failed while I was at speed and had swelled up waiting for me to push the clutch pedal down..."

I did? Musta been drunk.

What I see as happening is this: The clutch facing is made up of fibrous material, bonded together by an agent (resin). When a clutch is slipped (overheated), the resin is compromised ("baked out"). Clutches have a specified burst speed - usually 1.5 ~2 times engine redline. Compromizing the bonding agent lowers the burst speed from the original spec. The clutch could live forever after being "cooked", as long as the new burst speed is not met with the clutch disengaged (unclamped). As soon as you unclamp the thing (depress the pedal) with the trans input speed at or above the new burst speed - POOF!

Being in low-low introduces even greater issues, namely the 1.96:1 gear ratio.

With peak horsepower on a Tornado coming in at 4,000 rpm, we'll assume that as the specified redline. We'll then use 6,000 rpm as stock burst speed. 1st gear ratio is 6.398:1. In 1st geat, hi-range, we hit burst speed at a mere 16 mph. Shift into low range, and we hit the assumed burst speed at creepy-crawly 8.3 mph. Now, you gotta remember, with clutch pedal depressed, 1st gear, low range, the tires are driving the clutch through the transmission. Just because the engine is at idle, does NOT mean the clutch disk is happy. The pressure plate is loping around, but the disk is really humping along!

Then, suppose someone DID compromize the burst speed - you could have hit the reduced speed at 5 mph or lower. Coasting down a grade, clutch engaged, then push it in? Gravity will accelerate the disk pretty quick - BOOM!

The fact that just one side let go supports this- that was the side scuffing while whomever was slipping the clutch. It's bonding agent got baked out whereas the other side didn't, and thus had a different burst speed.


I made an Excel spreadsheet that calculates engine speed at any given transmission/transfer case combination. You can even plunk in different tire sizes (rolling radius, actually) and see what effects it has on engine speed. I can e-mail it.

That Bump_r....he does know everything!! Sounds like thats what did it..., I would have never figured that out...thanks Bob!!
The original that I referred to, I thought was on the old Yahoo board...just looked and its not there...musta ben an email...anyway, it had the level of detail and quality information your above post has...I'm sure you sent me an explanation but of course I may have butchered it somewhat in my retelling... :)
As far as "whomever was slipping the clutch", while a few people have driven my truck on occasion, easily 90% of the miles are mine...too much brute force I guess??

Bob,
Do you do math problems when you are bored? That was great.

Something else to add in is the age of the replacement disc. How many clutches for mid '60's J trucks do you think your local NAPA has sold in the last 20 or even 30 years. It could have been sitting on his shelf since he refilled his inventory after selling one in 1969 for all you know. I think Bob's math is the answer though.

Good point Barrman...could play into it certainly...
So how do I get a new one that is really a new one??

Good post bump !

Brute, you might be able to take your old disk to a clutch and brake place and have them put new linings on it. We have a few places here in Portland like Ott's friction supply that will build stock or custom brakes and clutches. I would imagine if you took your pictures in to them and asked their opinion they might have an opinion. Although I think bump is on the money..

brute: sounds like somethin in the pressure plate broke (springs) and let the clutch disk start slipping. they are made of asbestes and resins and other things. usually when this happens its because the material heats up and breaks down then dissenegrates. if the springs have broke, you may have a warranty issue to discuss with napa. you can tell by lookin at the p. plate and flywheel that you are easy on it. hope this helps some.

Interesting theory...wil take a look at that...priced a clutch/pressure plate and TO bearing at
Autozone today...for a 65 230 10 1/2 inch clutch...with the alignment tool, $149.99 and thats with a diaphragm type pressure plate...not the original lever type that I personally prefer...rather save some of that cash, I'll tell ya!!
brute4c