Little Blue 82

[Ray Cecil]

Ray, I can't say about a mechanical clutch.

With hydraulic there is a spring inside the slave that keeps slight pressure on the throwout all the time.

Yes, it is better for a bearing to be constantly spinning than accelerating from 0-3,000 (or whatever your shift point) and back to zero all the time.

The feel will get better and the sweet spot wider as the friction disc beds in.

Jim, I should have know better. Of course Gary has a nice factory adjusment procedure for the mechanical clutch linkage.

Although Jim, it seems to be suggesting that there be some freeplay before engaging the throw out bearing.

[ArdWrknTrk]

Jim, I should have know better. Of course Gary has a nice factory adjusment procedure for the mechanical clutch linkage.

Although Jim, it seems to be suggesting that there be some freeplay before engaging the throw out bearing.

Could well be.

Like I said I don't know the factors involved in the mechanical linkage clutch.

The 460, 6.9 and H.O. with external slaves all have a spring in them.

I'm more familiar with cable&arm for mechanical clutch release.

Don't really see the pivot mounted to frame and bell housing as keeping any kind of alignment, so maybe there is freeplay because of that?

 

[Ray Cecil]

Jim, I should have know better. Of course Gary has a nice factory adjusment procedure for the mechanical clutch linkage.

Although Jim, it seems to be suggesting that there be some freeplay before engaging the throw out bearing.

The Ford Service manual gary has posted specifies 1/2" to 2" of pedal freetravel before pressure is felt from the pressure plate. This, if I understand it correctly, suggests that the throw out bearing should not be engaged fully to the pressure plate fingers when pedal is fully retracted.

Also, just an observation. The old throw out bearing was basically toast. No grease left, dry as a bone, and the balls were rattling around. Im surprised it hadnt grenaded.

So, I am of the opinion, the less spinning it does, the longer it will survive.

Gary, Jim, Dave, Cory.....anyone else want to confirm my findings? Thank you.

[Ray Cecil]

Don't really see the pivot mounted to frame and bell housing as keeping any kind of alignment, so maybe there is freeplay because of that?

Possibly. Although my pivots and zbar are in excellent condition showing nearly zero play. Cory has sent me a spare pivot ball for the zbar he took off his truck. The rest of my linkage system is excellent as well, very little play. I find the mechanical clutch to be nice and easy to work with. Im not sure what advantages a hydraulic clutch bring....maybe it helps with the "feel"? Less strenous on the knees maybe?

[Gary Lewis]

The Ford Service manual gary has posted specifies 1/2" to 2" of pedal freetravel before pressure is felt from the pressure plate. This, if I understand it correctly, suggests that the throw out bearing should not be engaged fully to the pressure plate fingers when pedal is fully retracted.

Also, just an observation. The old throw out bearing was basically toast. No grease left, dry as a bone, and the balls were rattling around. Im surprised it hadnt grenaded.

So, I am of the opinion, the less spinning it does, the longer it will survive.

Gary, Jim, Dave, Cory.....anyone else want to confirm my findings? Thank you.

All of my experience has been with mechanical clutches, save for Big Blue. And I was always taught to have at least 1/2" travel in the clutch pedal before hitting the throwout bearing. As that appears to be in keeping with the shop manual, I'd say that's what you should have - at least 1/2".

[ArdWrknTrk]

The Ford Service manual gary has posted specifies 1/2" to 2" of pedal freetravel before pressure is felt from the pressure plate. This, if I understand it correctly, suggests that the throw out bearing should not be engaged fully to the pressure plate fingers when pedal is fully retracted.

Also, just an observation. The old throw out bearing was basically toast. No grease left, dry as a bone, and the balls were rattling around. Im surprised it hadnt grenaded.

So, I am of the opinion, the less spinning it does, the longer it will survive.

Gary, Jim, Dave, Cory.....anyone else want to confirm my findings? Thank you.

How old was your throwout?

35 years or more?

It's not the spinning that kills them, it's the sudden 0-3500-0-3500-0-.....

Balls skid in the races. The acceleration forces are huge compared to moving as fast as the engine changes speed, and even then there is no 0-650, or whatever.

It's similar to torquing a rod bolt. (Which is essentially stopped twice per revolution)

Come on Ray, you must have a lot of engineering background given your occupation.

[salans7]

Im not sure what advantages a hydraulic clutch bring....maybe it helps with the "feel"? Less strenous on the knees maybe?

Basically. I prefer a solid feel to my clutch, and I hope my F350 ends up feeling more solid than my Ranger because man do I hate the way my Ranger's clutch feels.

 

[85lebaront2]

Im not sure what advantages a hydraulic clutch bring....maybe it helps with the "feel"? Less strenous on the knees maybe?

Basically. I prefer a solid feel to my clutch, and I hope my F350 ends up feeling more solid than my Ranger because man do I hate the way my Ranger's clutch feels.

Having had vehicles with mechanical linkage clutches (1964 Falcon w/260 V8, 1966 GT350 w/Cobra 289) hydraulic (1958 F100, 1961 Mercedes-Benz 220Sb, 1963 Jaguar E-type) and cable (1965 Corsa 140 hp, 1980 Omni 1.7L, 1986 Plymouth Turismo 2.2, 1987 Horizon) I have mixed feelings.

Both the Falcon and the Shelby experienced failed Z-bars, in both cases one of the ends where the lever attached to the tube, the tube split on the tension side of the weld. The Corvairs were famous for snapping the ball off the front end of the cable (you have to see the way it was run to fully appreciate why it would break. Suffice it to say the ball did not swivel in the fork on the pedal and would fatigue fail the cable. Omni and Horizon (Turismo is a sporty Horizon) the cable worked well, but the self adjuster being plastic tended to "pop" and leave you with no clutch. The Hydraulic ones worked very well, but were prone to the same issues as brakes, water + brake fluid = rust.

Of the three, I like the cable system the least, it is stiffer and has less "feel" to it. Hydraulic ones I had usually worked very reliably, mechanical, in good condition with all the little "bearings" in the linkage are great, but bad motor mounts will cause no end of problems.

One item not addressed is the actual pressure plate design. There are three that Ford has used over the years, the Borg and Beck three finger coil spring apply design, The Long, three finger semi-centrifugal and various diaphragm spring styles.

The advantages and disadvantages of the three:

Borg and Beck style, advantage is high holding power and smooth action apply and release.

Disadvantage is high load holding and releasing particularly in slow moving traffic.

Long semi-centrifugal, lower spring pressure than Borg and Beck style, but clamping force increases with engine rpm.

Disadvantage is similar to Borg and Beck, but easier to work due to the centrifugal portion of the clamping force. Adjustment is critical, Shelby clutch specified 3/4" freeplay at 5000 rpm, and it did decrease as the rpm climbed.

Diaphragm, good clamping force, easiest to hold in as the diaphragm spring essentially goes "overcenter" as the clutch releases.

Primary disadvantage, clamping force weakens as the disc wears so the more worn the clutch is, the greater likelihood of it slipping.

[Ray Cecil]

All of my experience has been with mechanical clutches, save for Big Blue. And I was always taught to have at least 1/2" travel in the clutch pedal before hitting the throwout bearing. As that appears to be in keeping with the shop manual, I'd say that's what you should have - at least 1/2".

Bill, Shaun, Jim and Gary,

Thanks for the advice and opinions.

Gary, I think I will follow the factory advice as you have.

Jim, thanks for calling me out and keeping me on my toes. Im not a degreed engineer. Two year CAD degree, but I do work circles around some "degreed" engineers. The clutch was replaced in 2004 by the previous owner. I am assuming the throw out bearing was replaced then. The pilot bearing was in good shape, but I replaced it and the RMS anyway. I dont think I want to debate on throw out bearing longevity, and how to maximize it. Im going to do what the factory suggests.

 

[Ray Cecil]

Bill, Shaun, Jim and Gary,

Thanks for the advice and opinions.

Gary, I think I will follow the factory advice as you have.

Jim, thanks for calling me out and keeping me on my toes. Im not a degreed engineer. Two year CAD degree, but I do work circles around some "degreed" engineers. The clutch was replaced in 2004 by the previous owner. I am assuming the throw out bearing was replaced then. The pilot bearing was in good shape, but I replaced it and the RMS anyway. I dont think I want to debate on throw out bearing longevity, and how to maximize it. Im going to do what the factory suggests.

On another subject. While removing the transfer case, I noticed near the fill hole its embossed "ATF Only". Its an NP208.

So, I pull the drain plug expecting ATF, and gear oil comes out. I remove the tcase from the transmission and there is nothing, no seals separating the tcase fluid from the tranny fluid. Of course, the 4 speed uses 80-90. So I assumed Id fill everything back up with 80-90.

Why would the tcase say ATF only? There is no way you are going to keep ATF out of the transmission case if you fill the tcase with ATF.