Is there any possible way to measure or check the clutch disc thickness on an 84 F250 without removing the transmission? The trans shop is telling me my clutch is cooked because he measured the thickness of the disc. I haven't asked him if he removed the trans to do that but I can't imagine he would just to measure the disc on a whim that I might have the disc replaced. He says I need a new clutch, slave and master but I have a feeling the disc is fine and he's just telling me it's bad to sell me a clutch.

I'm pretty dumb when it comes to manual transmissions so I don't really know what symptoms are of a failing clutch but currently I am having a hard time shifting through gears. From what I read it can be air in the system or just a maladjusted clutch.

 

That would be a neat trick... I'd take it someplace else...

 

1980s trucks have firewall issues. The firewall will flex where the clutch master mounts. This causes a loss in travel by at the disc, making shifting more difficult. The firewall can crack, which makes the problem worse and adds the possibility of misalignment of the master with the linkage on the pedal side, causing the master to bind. Add rust to all this and it just gets worse.

This outfit sells a reinforcement.

ford firewall page

A clutch gone "bad" from a worn disc will slip in the higher gears. If yours is not slipping, and you get a positive engagement when shifting, your disc is fine. (by that I mean if you raise the revs just a little while shifting, when you let the clutch out, the clutch does not slip, the engine returns to the correct rpm and you feel a little kick in the back)

 

I am like standard trans illiterate. Right now, when I depress the clutch pedal at a stand still and shift into gear, when I let up the pedal about 1/2" or less, the truck starts to move. This tells me the clutch is ok, or am I wrong?

I'm thinking I need to start with an adjustment. I also crawled under there and it appears the slave cylinder is wet so maybe I have air in the system and a bad slave but I really have no idea where to start with diagnosing.

I think I'm at a dead end with this trans shop. I might not know much about these systems but I have a feeling they just want to sell me a clutch.

 

Is the slave cylinder wet with hydraulic (clutch/brake) fluid, or is it engine oil that has got down there?

The clutch shouldn't be engaging so close to the floor; some master cylinder push rods are adjustable, which will correct this, unless you have a firewall issue.

Forgetting the firewall for a minute, if the clutch plate was worn out, the pedal action would be higher, not lower like yours......& anyway, the plate can't be accessed to measure without a complete strip down.

 

So lemme ask a dumb question: when a clutch is "engaged", is the pedal down, or up? I'm assuming it is when the pedal is up.

And with a correctly working system, how far should the pedal travel from the floor before the vehicle starts moving?

 

Engaged: Pedal up, clutch disc clamped to flywheel by pressure plate, allows vehicle to move.

Disengaged: Pedal down, clutchy bits not touching, no vehicle movement.

Engaging so close to the floor might indicate insufficient disengagement, or a situation close to it. That can cause difficult shifting, and difficulty getting into gear at rest.

 

I personally like a clutch that engages close to the floor, at least in a car - it lets me pivot my ankle and not use my entire leg, that can be nice in rush-hour traffic.

 

Hydraulic systems have no adjustment unless you have replaced the master cylinder pushrod w/ an adjustable one.

If this is an '84 and needs to be squashed to the floor, check for a broken plastic pushrod retainer clip and then for firewall flex.
If the clip is bad and the pedal arm is okay it's a two minute $4 fix.