Toecutter:

You wrote: “I would think a hydraulic clutch would act very much the same as disc brakes would....it just needs that much more fluid to compensate for the cutting of the flywheel...much like disc brakes would if you were to cut the rotors down to make them smooth.”


No, not actually. The hydraulic system in a clutch is set up backwards from that of the hyd. system in disc brakes. With hydraulic disc brakes, piston travel into engagement (braking) is controlled SOLELY by fluid volume/pressure in the bores, which is why you are right about how the brakes work--disc brakes do compensate for cut rotors that are thinner than they were before cutting. But think about the design of the hydraulically-operated pressure plate--what pushes the friction surfaces together in engagement? Fluid? No. Not fluid, but mechanical spring pressure. Therefore the amount of hyd. fluid pumped to the slave cylinder, DURING RETRATION/DISENGAGEMENT, is irrelevant to how much friction face pressure is applied to the flywheel, during ENGAGEMENT, which is done solely by mechanical springs.

With hyd. brakes, there is nothing other than rotor runout to push the pistons back in the bores, after hyd. pressure is released. However, in the hyd. clutch, hyd. pressure is used TO RETRACT or separate the friction surfaces--when you push on the clutch pedal, the hyd. pressure pulls the clutch apart (disengaged), not into engagement of the friction surfaces, as brakes operate when you press on the brake pedal. That's why hyd. clutch's situation is REVERSED from the hyd. disc. brake scenario.

Consequently, what controls friction face pressure, and ultimately the potential for slippage during full engagement, is the amount of travel, and pressure, in the pressure plate springs. When you move the friction face of the flywheel forward, toward the front of the truck .025", for example, you’re now asking THE SPRINGS, not the FLUID, to make up the additional length. And of course, as compression springs reach closer to full extension, their available psi decreases.

So again, does anyone know for sure if any Ford pickup hyd. clutches have some capacity for adjustment? I have seen a hyd. slave set up in a van which mounted externally to the bell housing, almost identically to a purely mech. linkage. I’m betting this set up, if any, may have an adjustment bolt, but that any of the slave cylinders which mount directly around the input shaft are unadjustable, simply b/c there is no mechanical access. Can anyone clear these two scenarios up for me?

Thanks,

BigSix

 

ACK!
Your right.....wasn't thinking about the fingers on the flexplate are what actually provides the pressure for the clutch disc itself....

I've never had to have a flywheel cut down...how is it done? Is it cut all the way across the flywheel, or just in the area where the clutch disc is making contact?

Like I said, I would definitely start looking into that place as far as screwing you over. I've gotten the shaft before by certain businesses, and trust me, they've been shafted back twice as hard, if not worse. I make sure everyone knows what kind of lousy service they give.....

Later
Phil

 

Everyone I have ever had resurfaced was cut down all the way across.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

Yes, the flywheel I had cut was also cut all the way across. However, as to how to arrive at the correct amount to cut, in my naivete I assumed it was either marked, like a brake rotor, with a min. thickness, or that the shop had a book which gave safe cutting values. I didn't want to become the poster boy for U.S. Scattershields, Inc.! (I know that's unlikely at big six RPM's, but I've heard of big rigs shot through, literally, w/ shrapnel from exploding clutches, and they don't even wind as high as the 4.9.) Anyway, the shop had no book, the flywheel didn't say, and they just cut .028" off of a very heat-blued and cross-cracked flywheel. They said "Yeah, we generally cut about .025" off, unless it's real bad. It came out looking new and worked beautifully w/ a LUK pressure plate, disc and throwout bearing kit from Summit.

I don't know how it's supposed to be done, but they seemed to know what they were doing. I have been satisfied w/ other machine work I've had done from them as well. Still, I've got to believe there is a published guide somewhere, so that less experienced (lucky?) shops don't overdo it and create an "exploder" but cutting too much off. Anybody?

 

Whew!! This topic has alot of stuff in it. Let's see, first:

How a clutch can go right away: If the pedal linkage is not checked for travel then the clutch will ride all the time and ruin it. A new clutch must be babied to properly break it in.

How to adjust a hydraulic clutch (concentric): The manual says to push the pedal down slowly and pull it back up quickly. I believe there is a pressure check valve of some sort in the slave assembly. I have seen the bleeder screw squirt pressure when released.

Flywheel resurfacing: They MUST cut down across the whole disk or the pressure plate mounting surface will not be at the same level as the disk. The Ford manual has a limit on the cut down thickness, don't know it off hand, but a stock flywheel can be safely cut about 3 times if cut correctly.

Blue burn marks on the flywheel: This is signs of overheating the flywheel by draggin the clutch. It usually occurs when the pedal is not adjusted properly and also results in a improperly bedded clutch and quick destruction.

Clutch surface area: There are two types of clutches for F150's with the Mazda tranny. A thin surface contact and a wide surface contact. Be sure to replace with the same type.

I think that covers all of the Q's.

Randy

 

Am I missing something here?

You resurface a flywheel -- then you bolt the pressure plate ONTO the face of the flywheel. I do not see an increase in the distance the pressure plate springs must travel to maintain face pressure. As far as I can see, there is no change in pressure plate travel; its fixed to the flywheel face.

Now the clutch disengagement, or the distance a throwout bearing must travel, -- OK that changes, since the flywheel face is now farther fron the transmission.

I suspect the minimum thickness for the flywheel has more to do with rigidity and the ability to dissipate heat rather than pressure plate movement. I guess if you shave too much off, you are also moving too far from the T/O bearing and will have trouble disengaging the clutch. ... Because all three, the flywheel face, pressure plate, and clutch disk, (as a unit) have moved away from the base of the throwout bearing (the base being the trans or bell housing). But the clutch will be adequately engaged (since the disc is trapped between the pressure place and the flywheel until released, unless the disc is too thin)

Or am I as lost as my wife says I am?


Raul
w/ 81 F-100, I6, SROD, Carter 1V non-feedback carb, no A/C, no PS, no PB, but it gets me where I need to go

 

Brad, Yes, it is our oldest truck. 1980' LTS-8000, 3208 cat engine, Fuller 13 speed Roadranger trans. Nothing like getting behind the wheel of one of these and double clutchin' down the road. After the ol' foot gets tired, I just go to floating the gears. Gotta' love it. I never drove a tractor trailer but I have been behind the wheel of these babies since I was about nine years old. It's just like riding a bike.

Jakegypsum // Ford fleet, soup to nuts.

 

We had a flywheel cut once just a little past the limit. Very, very small amount. Put the whole thing together and found out what happens if you pass the limit. The clutch would not disenguage properly. Not enough reach with the fork and throwout bearing. Shifting was very rough. It was easier to shift without the clutch. This clutch had a mechanical linkage setup which would not work properly with the flywheel cut too thin. A fraction past the limit. I have not seen but have heard numerous stories about flywheels blowing apart because of being cut past the limit. Big rig stories. It is not worth the aggravation if there is any question about the flywheel. Replace it when in doubt.

Jakegypsum // Ford fleet, soup to nuts.

 

beginning in late 85, there is adjustment in the hydraulic clutch. get your self looking up under the dash to the passenger side of the steering column.you will see a rod coming out of back of slave cylinder that connects to clutch pedal linkage. this should have a nut setup that is on the THREADED rod. loosen this and spin the rod until you get freeplay if you have none( if you have none, you will go through clutches more rapidly, since it is not fully releasing the pressure). if you want more pedal travel, spin it the other way.
i put the adjustable rod in my 85, it is about 15.00 dollars.before i bought the truck, the previous owner put in a clutch at 15,000 miles, i put one in at 26,000 and needed another at about 40,000. this is when i found out about the adjuster !! i got 70,000 or so miles out of next clutch.

 

Jake, I hear ya on that. We had a 75 Frieghtliner conventional about 10 years back we ran as a local truck. It had a 903 Cummins with a 5 and a 4 trans. what a handful to drive. lol. Manual steering gear to boot. I finally got the hang of leaving the aux in 3rd range and just shifting it like a 5 speed (sorta) That brings back some memories. Take it easy!

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

Oh Man Brad, I hear you on the 5 and 4. We had a 73' International 2010 Fleetstar straight job truck. 549 V-8. 5 speed trans with a 3 speed trans/transfer case. You had to be a master to shift that thing. No syncromesh at all. If you missed one gear slightly, you would be pulling that sucker over. Downshifting was a separate art. Then there was the higher gears you would shift from 4 low to 5 low. Then shift back to 4 high, then shift to 5 high. We used the transfer just to split the gears. We never used all three. That really got out of control. The old girl did move out though. She was a drywall boom truck and I can say that I did have her up to 90 mph at one time. Never again! It took me a long time to learn how to shift that thing. We also had a Ford Lts-80o with a 5 and 3. It was the same type of truck with a 391 under the hood. It was under powered big time. Nothing like running through 8 gears to get to 35 mph. City driving was real tough. Lol. Times and trucks have both come a long way. Jake.

Jakegypsum // Ford fleet, soup to nuts.

 

I hear that Jake. My Dad's personal truck is a 97 Peterbilt 379 (classic style may have the numbers wrong) With the extended hood and the american classic interior package. It is total air ride with an air ride cab and the unibilt sleeper. Rides better than my F350. lol. It has a 3406E Cat (575hp) with a fuller 15 speed. Shifts better than most pick ups I have driven. The 15 is good for pulling the flatbed like he does but I still prefer a 13 speed for the closer gears and it feels like the final drive is higher. As long as it isn't a super 10 (stupid 10?) I am happy. Take it easy Man.

Brad Godkin
1986 F350 CC/SRW
6.9liter/C6

 

Brad, Yes, the new big trucks are unbelievable. I was thinking the same thing as I was reading your posting. The new big trucks do ride better than a lot of the pickups. You gotta' love the air ride trucks of today. They ride better than some of the higher quality cars that are out there. Smooth.

Jakegypsum // Ford fleet, soup to nuts.

 

For the guys talking big trucks, I can't tell you how many Spicer clutches that I get get back because the customer said " It don't want to work right for my customer, so, it must be a defect in the pressure plate, so, I need another one !" Most of the time, it's how you adjust the clearance at the stop clutch...period ! And, if they would actually read the wall size chart that comes with EVERY Spicer boxed clutch, they would know that you have to apply grease,by hand, to the stop clutch surfaces. This blows there mind when I mention it and actually show it to them in print ! But back to Ford pickup's, Before I talk about the adjustment, I first will say to install the 3 dollar reinforce plate at the clutch master for ANY Ford truck, even if there isn't a problem....you will need it in the future anyway. Now I need to give RGAZ credit for this next comment, the adjustment is done by removing the cross shaft lever under the dash and repositioning it so as there is no slack between it and the pushrod/clutch master while the pedal is in the resting position, thats if the 3 dollar plate doesn't take care of all your shifting problems. A new lever is 12 dollars. I beleive all of this only applies to 87-91 year models, older and newer have other provisions such as the adjustable push rod which is for the older models. What the 92 and newer have to offer, I dont know. As far clutch chatter, if resurfacing the flywheel doesn't cure it, replace the flywheel with a brand new one (tried,tested & trued).
Phil

 

[font size="1" color="#FF0000"]LAST EDITED ON 02-Mar-01 AT 02:41 AM (EST)[/font][p]Raul:

I'm embarrassed to have to quote Billy Joel to you, but "You may be right!" I've got to conjure on this somemore, but you may have a point on the relationship b/w pressure plate and flywheel staying the same after cutting. I want to go look at my old p.plate, if I still have it.

Phillip: RGAZ made other contributions, but it was Billyb. who told how to adjust the concentric (this means around the input shaft, in this case, right?) hyd. clutch, wasn't it? Billyb.--thanks a MILLION. I haven't remembered to check this out when I've had my "grubbies" on yet, but I will soon!

Phillip: Can you give me some more detail on this "$3.00 plate?" What does it do--is it a shim of some sort, or a reinforcement, as you imply? What is the FoMoCo name for it and what, exactly, do it do?

Thanks all,

BigSix