Replaced my 79 12a with a rebuilt 85. Used the 85s clutch disk/plate etc but now installed the clutch feels different. Instead of feeling resistance at top then as depressing the resistance stays consistant or even gets less when the pedal is completely depressed, now it feels like its getting harder the farther it goes down. Almost like pressing a spring instead of moving something.

It still shifts but it feels as if the clutch is only halfway depressed and the syncros are working overtime. I have to put a bit more umph when I shift to get it to fall into gear and there is a slight grinding.

I bled it but no help. Is th e throwout bearing different or something that I should have changed?

 

Which car did the flywheel come from? The 79 flywheel uses a 215mm clutch and the 85 uses a 225mm clutch. You can go 79 disc to 85 but not 85 disc to 79. Also, the flywheel needs to match the engine rotating assemby.

 

The clutch and flywheel matches the engine. I have the 85 clutch and flywheel that came with the engine. I'm just wondering if maybe the slave cylinder travel should be different or maybe the throwout bearing is different or something that would explain this.

 

In rod we trust.

 

You are pressing a spring, that's what all those fingers on the PP are.
I would check the slave cylinder. I don't know why but they tend to self destruct. I carry a rebuild kit wherever I go. I had one die and when I pulled the piston, it was ground down at a 45 degree angle.

If your clutch pedal sticks to the floor, that's usually the master cylinder. If you have to replace either part, buy them new, don't waste time rebuilding one you don't know how many times it has been honed out.
If you use silicone brake fluid, it also helps with the absorption of water which causes the corrosion in the first place.

You are still using the '79 tranny? Since the slave cylinder attaches to that, it's the same one you had. How much play do you have at the top of the pedal? If it is a lot, the clutch isn't releasing all the way. I thought '79s were very slightly different in their master cylinders in that and an FB one won''t fit without a little massaging but I don't know if the inerds have changed.

Did you change the pilot bearing? If it has self destructed like they all seem to do, this might be why you're getting some grinding when shifting.

 

Reused everything and kept the 79 trans. I did have quite a tough time getting the engine to back up to the trans. Hope I didn't damage anything but othere than the clutch feeling it drives like a champ. If I do a bit of rev matching while shifting I wouldn't know anything was wrong except the initial puting it into first or reverse from a standstill.

There really doesn't seem to be any play till resistance in the pedal begins. I drive 5 other manual trans vehicles and know what that feels like. It just feels like its pushing but not succeeding in its goal and pushing against an object that won't move correctly. I have just replacing a slave just for the heck of it. Its not much money but if I replaced a part every time I suspected it might be the problem I would be flat broke.

Is there a way I can test the slave? On my vette it is bad when it starts leaking but there is no fluid build up or anything. So I just yank the rod out of it and see if it still looks normal?

 

Did you use a clutch alignment tool? If not and you let the tranny hang while the input shaft was in the clutch, you can bend the clutch framework and that results in some weird issues. Also, if it wasn't aligned right, you could have destroyed the pilot bearing but since ever rotary I've change the clutch or engine on has had only the worn outside frame of the pilot bearing, that might not be an issue unless the needle bearings are in the process of destroying themselves.