Clutch Issue after clutch issue!

[Cecoda]

Hey I'm Cecoda. New to the group! Glad to be here!

I have a 79 Chevy with a nv4500 in her. Worked good for 3 years. Then my buddy gave me a mini starter. I took the slave off to make it easier and to not break it. Put the starter in and put the slave back in. Then the clutch fork wasn't moving enough to disengage the clutch. Just got a 70 Gmc so I drove that instead. Replaced the master, slave, and had a braided line made. Same problem. Now we come to last night. Pulled the trans out, replaced the fork, throwout, ball pivot, clutch, and pressure plate. Now it will move! After months! Buutttt it is wrong. The pedal is just in the bottom half of the travel. The first half has a lot of pressure but when it hits half way the pedal feels like it should. When I pull the pedal out. It is either fully engaged or fully disengaged, no in-between.Things to note: the new clutch is a 12" and the last one was 11". Cutch fork ear spring on the new one was slightly a different design. And Finally, the throw out was slightly different as well, it wasn't solid on the rear side like the old one, but the front side is the same.. What are yalls thoughts?

[Rickysnickers]

Welcome. I am going to move your post to the appropriate forum. This is currently in the pre '47 area.

[kwmech]

Why did you replace the clutch when it was working fine and confuse the problem. Sounds like air in the hydraulics. I doesn't take much air to create a problem in these systems as it only takes a couple of air bubbles to make you pull your hair out.

[Cecoda]

I was taking the transmission out anyway for the fork and throwout so I put a clutch in too. This truck has been sitting in my shop for months and on my day off I'll work on it. I have bled and bled and bled that line and it wouldn't push the fork in enough to engage the clutch. So I decided the problem was internal.. I take the trans out, put it back in with new parts and now the hydraulics push the fork all the way in like it should. But I'll bleed it again just to be safe. The slave was out for a couple days while I was working on it.

[Cecoda]

@Rick Thank you!

[geezer#99]

From what you describe I think you have the wrong throw out bearing.

[Cecoda]

Can you explain to me what makes you think it is the throwout?

[geezer#99]

Because of where the pedal sits.
Likely you have a short tob.
You need a long one.
Pic in here.


http://67-72chevytrucks.com/vboard/s...d.php?t=332574

[Cecoda]

I see. My old throwout bearing and the new one are the same size but that is a big difference in the picture. I wonder if I have been running the wrong one all along. Though that picture is from an sm trans not a nv trans

[79vette]

what method are you using to bleed the clutch?

Is the TOB you are using the one which came with your clutch kit? Or is it different one you got from somewhere?

[Cecoda]

The tob that came with the kit. Also I have bench bled, in truck bled, and thanks to the custom hydraulic line I can basically bench bleed it while in the truck. Spent many many nights making sure there was zero air.

[79vette]

ok. It sounds like you have all the correct parts installed then. As long as you are using the matching pressure plate and bearing from the kit it should be good.

You mentioned you also replaced the fork. Any chance you might have used the fork from a mechanical linkage clutch by accident? It is a different length and shape from the hydraulic fork, and probably would not work right. Is your bellhousing original to the truck?


The best way I have found to do square body hydro clutches is to just install all the new parts dry. Connect the hoses, leave the slave cylinder unbolted from the bellhousing and fill the reservoir, and slowly press the rod into the slave cylinder. Then let go and allow it to fully extend under spring pressure. Do this 10 times or so while checking to ensure there is still fluid in the reservoir. Let it sit for 10-15 min and any remaining air will bubble out of the master cylinder and you should have the clutch completely bled. My 88 R30 has a factory hydro clutch, my 86 K5 was retrofitted to a hydro clutch with stock parts, and my C3 Corvette has square body clutch hydraulics and this method has worked great on all of them.

If you do try to bleed it some more, I would just unbolt the slave cylinder and slowly push the rod in and let it extend back out 5-10 times. At that point you should have no air in the system.

[Cecoda]

Everything transmission related is a 93 chevy in this truck. The fork was the exact same shape and size just had a slight difference in the ear spring but still held the tob good. I think this may just be a stout clutch and I haven't driven the truck in a couple months (though my daily is a mechanical clutch, so I dont think it is unfamiliarity). I think I'll drive it around for a while and see because I still have my suspicions. Thank you guys for the help!😁