Clutch issues w/swapped in NV4500

[arveetek]

I have a friend who has an '88 Chevy 1500 4x4 that originally had a 350 gasser w/NV3500. He swapped in a 6.2L and a later model NV4500. I've helped him get the engine running, but he can't seem to get the clutch to work. I don't know a lot about these systems, but I know that he has a hydraulic setup. The pedal pumps up firm, but it doesn't seem to move the clutch far enough to disengage from the engine. He's pumped and pumped, and bled and bled, but it doesn't seem to help.

What should I check for first? I've never messed with the NV4500 setup. I'm an auto guy, myself.

I'm not sure what flywheel or clutch combo he used.

Casey

[Yukon6.2]

Hi
A guy i know was having the same issue with a GM gasser last year.Turned out he had the clutch plate in backwards.He tried changing the slave,master cyl and line with no luck.
The clutch system is bled differently than the brake system,that may be the problem as well.
Good luck
Thomas

[trbankii]

I know that I had a devil of a time bleeding my clutch when I replaced it the other year. IIRC, the bleed screw is on the side of the slave and I had to jack the passenger front side of the truck up to get the bleed screw to point "up" enough to get all the air bubbles out.

[arveetek]

The clutch system is bled differently than the brake system,that may be the problem as well.


Could you explain further please?

Thanks

Casey

[HH]

Bleed screw is on the top of my slave cylinder. I just opened it up and let the air out. Pumped the clutch a few times and let more air out.

Are the clutch fork and ball in good shape? Installed correctly? Are they the right parts?

[NH2112]

On my Ford you have to fill and bleed the slave cylinder before installation. This is a real PITA, but it's the only way to get something even remotely resembling a firm pedal.

Assuming it's a late-enough model not to have the concentric slave cylinder, I'd remove the master, hose, and slave as a unit, clamp the slave in a vise with the hose port as close to the top as possible, and have someone else hold the master high enough to take any bends or kinks out of the hose while you work the slave pushrod in and out. You'll know when the last bit of air is gone.

[Yukon6.2]

Hi Casey
I'v had the best luck letting gravity do the bleeding on clutch systems.I open the bleeder and watch the fluid coming out for air,close the bleeder and cycle the pedal a couple of times.Repete as nessesary, The first one i tried to bleed like brakes we used two bottles of fluid and never did get a firm pedal.
Sometimes they can be a real pain.
Good Luck
Thomas

[jggiedeman]

I contacted LUK clutch tech folks on my swap. I had a military rig with the 6.2. I installed a 98 NV4500 with internal slave cylinder setup. The clutch they had me buy was not the standard 6.2, 6.5 found on the web. Had everything to do with the length of the bell housing, internal slave cyinder setup and a 6.2 vs a 6.5. So maybe the clutch diaphragm needs to be a certain height. Food for thought.

Sounds easy but I do believe LUK clutch was purchased by another company.

[Drifter]

I contacted LUK clutch tech folks on my swap. I had a military rig with the 6.2. I installed a 98 NV4500 with internal slave cylinder setup. The clutch they had me buy was not the standard 6.2, 6.5 found on the web. Had everything to do with the length of the bell housing, internal slave cyinder setup and a 6.2 vs a 6.5. So maybe the clutch diaphragm needs to be a certain height. Food for thought.

Sounds easy but I do believe LUK clutch was purchased by another company.

I know this thread is very old but how can a clutch from a 6.5 not work on a 6.2? Do you have a part number on the clutch you used?