Clutch won't disengage after driving under load

[Chewy1576]

Today I was pulling a 27' travel trailer over a mountain pass. Starting out and for the first 15 or so miles on fairly flat roads, the clutch would disengage and transmission shifted just fine. When climbing the pass and shifting between 3rd and 4th, it became harder to shift. It felt like I was fighting the RPM shift limiters because the clutch wasn't fully disengaging. Anyone know what would cause the clutch not to disengage after driving for a while? This isn't the first time it's happened either. It happened when hauling a load a gravel and trying to work the truck into a tight back yard to unload.

The transmission is an NV4500 swapped in place of an SM465, NV4500 master/slave cylinders, Jegs flywheel, Hayes 12" super truck clutch, NV4500 throwout fork and SM465 throw out bearing.


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[Chewy1576]

Also, would the clutch not disengaging keep the engine from running? It also won't start...


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[Justin S]

by not starting, are you saying it won't turn over? Even if it wouldn't disengage, you should still be able to start it in neutral, unless its stuck in gear internally for some reason

 

[Chewy1576]

It does turn over with the clutch pedal depressed, and there is fuel coming from the injectors. I'm thinking no spark is keeping it from starting and running. I have already replaced the ICM, next may be the coil.


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[Justin S]

So you're having multiple issues at once then. I remember you had another thread with the clutch issue, I know you said you tried bleeding it out multiple times, but all I can think is that for some reason maybe the fluid is getting too hot and causing your issue?

 

[Chewy1576]

You may be thinking of another thread. I recently replaced the SM465 master and slave cylinders with a sealed set for the NV4500 for this issue, but I guess that wasn't the problem. I'm still running the SM465 throwout bearing with the NV4500 though. I think possibly that bearing is not allowing the clutch to apply full pressure to the flywheel and it's slipping. I was running 3000-3500 RPM in third gear climbing some long hills. I was at the top of a hill and trying to shift from third to forth when I noticed the clutch wasn't disengaging anymore. That could generate enough heat to just bond the clutch plate to the flywheel. Then the motor cut out as I was doing 50 MPH. I got it to start again and tried to get moving but it died again. That was the last I could get it to start.


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[77Impala]

First verify that there is or is not any spark. If spark then check fuel pressure. Might check all fuses as well.

 

[Chewy1576]

Had a few minutes to test a few things today.

After sitting for a few days to cool off and recharging the battery, it still won't start. Hooked up a timing light to the #1 plug wire and as I suspected, no spark. The distributor isn't more than a few months old and I replaced the ICM Saturday. I picked up a new Accel coil and spark plugs today and will be replacing those when I get more time. I'm doing plugs too because the one I pulled on Saturday to check for spark before the battery died was almost black. There were periods of time I was running really rich while I was figuring out the tuning so it probably should be done.

 

[Chewy1576]

The culprit was the ignition coil. Replaced it with a new Accel SuperCoil and it fired right up. Took it for a test drive and it shifted fine too so I'm completely lost on that. I'm still going to have it looked at though. I don't think that throwout bearing is the right one or set up right.


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[Chewy1576]

Put some miles on the old truck today. Starting out this morning everything was fine. It went in and out of gear just fine. As the day went on and things heated up, specifically this last half hour driving home from work, it became harder to go into 3rd or 2nd gear. I even tried reverse and just heard gears grinding. The clutch isn't releasing the flywheel and the input shaft is still spinning. Also during the bottom third of the clutch pedal travel, it sounds and feels like something is grinding in the pedal.


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