Hello! I just installed a new Sachs flywheel and clutch on my 1995 Chevy 1500 4x4. Got everything back together, filled up tranny fluid and gear oil, bled the clutch till no air came out and it still won’t shift while the engine is running. I can get it into reverse with a little grinding when in 4H, but that’s it. The stick moves freely when the engine is not running. Checked the master cylinder and it is moving just fine. I have checked and did not install the clutch plate facing the wrong way. Any other guesses on what I can do before I have to drop the transmission again and redo the whole install? Thank you very much in advance 
The clutch master cylinder may be leaking internally and not applying enough hydraulic pressure to operate the slave cylinder. While watching the slave cylinder have someone operate the clutch pedal to see if the slave cylinder operates thru it’s full range. If not, the master cylinder is leaking internally and requires replacement.
Tester
Is it a new pressure plate? Does it have stronger springs? Your current master or slave cylinders may be tired or leaking.
Could be something wrong with the pilot bearing too. except for not disengaging, does the clutch pedal feel normal? does it have the usual inch of free play at the top and does the friction point feel about right?
It is also possible that you have the wrong clutch assembly, i.e. the movement of the pressure plate or the clutch plate thickness might be off. Maybe a bad throwout bearing too.
It is a new pressure plate, I’m not sure if the springs are stronger. I will check the master cylinder function tonight. I really appreciate it.
Keith the kit came with a new pilot bearing and throwout bearing. Yes besides not disengaging the clutch does feel right. I got the new clutch kit and new flywheel from O’Reilly’s auto-parts and they said that they were the right parts for my make and model vehicle.
Just because O’Reilly’s says its the right one doesn’t mean that it is the right one, or that the parts in the box are the correct parts. I had this issue once with a car. It was an 86, but there was a small change made in the clutch design from the 85 model. Turned out that my car was a very early 86 that was made in 85 and guess what, the 85 clutch fit, or so I thought.
I bought that clutch kit from AutoZone. A few years later, and about 100k miles later, I put a new engine in it and decided to replace the clutch with a factory clutch. Turned out that AutoZone had their numbers backward. I have also found the wrong parts in some boxes, i.e. I ordered left and right calipers for one car, the boxes were labeled for left and right, but when I got home, I had two lefts and no rights.
How would I check to make sure that I got the right parts?
You might check at various sites, like rockauto.com, also see if Sachs has a site that lists part applications. A wrong part would be a good first guess, as @keith said.
Checked the Sachs catalog and I was sold the right parts.
From reading what I can find since it wasn’t the wrong part it is either the master/slave cylinder, or fork. Is that correct?
Try this, Shut off the engine, but have the truck pointed in a direction that you can drive off in. Put it in second gear, push in the clutch and start the engine, then let out the clutch to the slip point, but let it slip for a few seconds, maybe up to 5 seconds. Then see if it begins to work correctly.
When you start it with it in first gear on flat ground, holding the clutch down and releasing the parking brake, does the truck start to creep?
Thanks Keith I will try that tonight as well. Yeah, it pulls forward with the clutch pressed down after I let off the brake.
Looks like I will have to try those things tomorrow night. My “shop” is in use tonight and my “assistant” is unavailable will post to let you all know what the outcome is. Thanks so much guys for your help so far!
That’s what it sounds like to me.
If the clutch pedal operates through its full range, but the slave end doesn’t move through ITs full range, than you have an internal leak in one or the other.
It’s customery to change both, because the piston seals are both exactly the same as far as wear and age. If one is leaking internally, chances are that the other is on its last legs too.
I had the same problem, but I knew what I had done, I put the disc in backwards.
I desered every minute of misery taking the trans back out and fixing it.
If it’s the slave cylinder, hydraulic fluid would leak out of it each time the clutch pedal is depressed.
But you’re not going to believe this. My clutch master cylinder just failed today. Pulled up to a stop sign, stepped on the clutch pedal to put in it first gear, no go.
Guess what I’ll be doing tomorrow?
Tester
I’d change slave cyclenders everyday compared to cooling fans that wont come on when they are supposed to.
Have you tried pumping the clutch pedal quickly several times before trying to shift? If that works, it’s an indication that the clutch master (or slave) cylinder needs replacement or they still contain some air. I think the first thing I’d do is bleed it again. Also, there may be a separate mechanical adjustment in the linkage between the slave cylinder and the clutch release arm.
Tester that sucks man I’m sorry to hear that. On my way to the shop to try and figure this out. Will check in in a few hours and let you all know how it’s going.