Originally Posted by ihatebarkingdogs

How is Reverse? Does the car back up normally? I assume this is a 4+3 transmission?

Originally Posted by jv9999

How many miles on the clutch and trans? Smell anything burning? Been servicing the OD unit every 10K or so? Any odd noises?

Originally Posted by MatthewMiller

I don't think it's clutch hydros, because the default mode for a clutch is to be full engaged. The hydraulic release system's failure mode is usually the opposite: they don't fully release the clutch when you press the pedal down.

Originally Posted by 84 4+3

True. Do you think if the slave got too hot it could be hanging up in its bore? The pedal feel completely changed when this happened. Maybe pressure plate...

Originally Posted by MatthewMiller

As in, maybe it's not returning all the way back after you let the clutch pedal out? It's possible, I suppose. I was going to suggest that the pressure plate spring (is it diaphragm on those? not sure) might be doing something funky. The thing is, either of these explanations assumes that the fundamental problem is the clutch slipping. I would have thought you would smell it burning as much as you were "on it" when this first occurred. But maybe not. I can't think of anything that would give the clutch pedal a strange feel and disconnect the engine from the drive wheels in the way you describe that did not involve the clutch slipping.

Originally Posted by ihatebarkingdogs

By "topped out" do you mean that you had 'high' RPM when you shifted into 2nd? If = yes, I think the pressure plate hung up from centrifugal forces. I had it happen with a Borg and Beck 3-finger pressure plate in one of my early cars I had in High School (late 60s). I've heard of centrifugal-release occurring with diaphragm clutches, but it has never happened to me.

If it does it again, or begins to do it frequently, and high RPM is the factor causing it, the pressure plate will need to be replaced. Diaphragm spring pressure plates are susceptible to being bent or distorted during installation if the bolts aren't very carefully, incrementally, tightened. If it got distorted during installation, this behavior at high RPM could be a result. Another possibility is that some bit of material broke off and lodged in the pressure plate not allowing it to engage.

I'm with Matthew Miller: If it was slipping, you should have smelled it on the way to the house. Unless the friction material is non-organic, ie metallic. In that case it would just smell "hot".

My guess is that you will be taking the clutch apart for inspection. Something went wrong.

Originally Posted by ihatebarkingdogs

I don't use a star pattern on clutch pressure plates. I feel that the pressure plate is distorted less by going around it rather than back and forth across the entire diameter of it with the "star pattern". I go around every-other bolt 1/2 turn for the first three, then go to the other three and 1/2 turn every other bolt. Repeat until tight-ish, and torque to final. Think of it as a 'spiral-down' instead of a rocking back and forth. With the spiral the next bolt tightened is only a few inches from the one with the most load on it (the one you just did). With the star pattern, the next bolt tightened is almost straight across from the last bolt tightened. The load is transmitted across the entire cover, not just the few inches of the same side.

I was curious as to what the FSM says, so I looked in my 85 FSM:
"Install a bolt in every hole and tighten down evenly and gradually until tight to avoid possible clutch distortion. (Cover loads are as high as 1-1/4 tons.)" So the FSM doesn't get very specific either.

I doubt these parts are delicate enough to be sensitive to what bolt pattern is used to tighten them is as long as the bolts aren't just rammed down with an impact. I think some little bit of something broke off and got lodged in it. I think it will be obvious what happened when you take it apart and conduct a CVI. (Close Visual Inspection).

Originally Posted by Tom400CFI

I had a clutch in a Camaro that did a similar thing: I launched it at the drag track (on street tires so by "launch", I'm talking 2.0x, 60'), hit 2nd with a flat foot shift and something "let loose". I babied the car back to the pits and began trying to assess what went wrong. By then, it seemed fine, so I staged again, and on the launch it was as if the clutch wasn't hooking. I was like slipping....but jerky and rough. Weird. I got out of it right away and babied it down the track, back to the pits. Loaded it up and headed home. I made it about 1/2 way home and she let go all the way. I coasted off the hwy, into a parking lot and called for a ride. Later, Picked it up w/a trailer, took it home and pulled it apart.

The verdict? The splined/hub part of the clutch disk had ripped out of the outer part of the hub and was spinning somewhat freely inside the outer hub. I'd guess that initially, it tore apart, and then caught on the roughly torn metal "spokes"...and that is why I was able to drive it again. IDK why it let loose for good, driving home on the highway....but it did. I needed a new disk.

Originally Posted by Tom400CFI

I had a clutch in a Camaro that did a similar thing: I launched it at the drag track (on street tires so by "launch", I'm talking 2.0x, 60'), hit 2nd with a flat foot shift and something "let loose". I babied the car back to the pits and began trying to assess what went wrong. By then, it seemed fine, so I staged again, and on the launch it was as if the clutch wasn't hooking. I was like slipping....but jerky and rough. Weird. I got out of it right away and babied it down the track, back to the pits. Loaded it up and headed home. I made it about 1/2 way home and she let go all the way. I coasted off the hwy, into a parking lot and called for a ride. Later, Picked it up w/a trailer, took it home and pulled it apart.

The verdict? The splined/hub part of the clutch disk had ripped out of the outer part of the hub and was spinning somewhat freely inside the outer hub. I'd guess that initially, it tore apart, and then caught on the roughly torn metal "spokes"...and that is why I was able to drive it again. IDK why it let loose for good, driving home on the highway....but it did. I needed a new disk.

Originally Posted by MatthewMiller

That happened to me at an out-of-town autocross with Danny Popp riding shotgun. But mine let go suddenly and completely and never pretended to work again. I know what you mean though - when removed from the car it took a lot more than just hand pressure to spin the hub inside the disk. Based on the most recent posts by the OP, though, I really doubt you could lay down black strips if the hub were broken in the disk.

84 4+3, to me the big wild card in this equation is that overdrive clutch. After watching this video, I now understand why IHBD was asking how the car feels in reverse. Does the problem feel the same when the car is in OD vs not? There are the clutch packs in there to worry about as well as that front bearing that can disintegrate if it's installed with too much preload. That said, none of this would explain the weird pedal feel.

Originally Posted by InfomanSS

Any updates, 84 4+3? I was planning on getting the same clutch kit, so you have my attention. :-)