NV4500 Odd Pedal behavior

[OK93K1500]

Hello everyone! Recently picked up a 94 heavy half 4x4 with a NV4500 transmission (factory, not swapped). I’ve googled high and low but I just can’t find something that fits the issue I’m having. The pedal binds pretty badly as you near the end of travel. It’s smooth and then the last inch or so you have to push pretty hard and it just sort of lightly “pops” to the floor allowing you to start the truck.

When it comes to releasing the pedal, again, it binds. It “pops” the first inch or so of travel and is smooth all the rest of the way. This makes it insanely rough to start out in first of reverse as it engages through that first inch of travel and usually there’s no way to make it smooth. It’s not sticking to the floor, it’s not spongy and once you’re moving it’s fine shifting between gears. It’s much worse once it’s warmed up, it’s actually smoother when cold. The previous owner recently had the clutch/flywheel/pressure plate/throwout bearing/pilot bearing all tended to, I’ve got the receipts. About 6 months/10,000 miles ago.

Any ideas where to begin? Fluid on the clutch master cylinder is almost black, could it be time to change the master cylinder/slave cylinder? Could it be the linkage to the master from the pedal?

thanks for any tips you can offer!

 

[Supercharged111]

I had a similar situation when I tried purging the fluid on my LT1 (T56). I developed shifting issues which ended up being my pilot bearing. Shortly after I began the purge, the pedal decided at about half stroke it'd turn into a rock. I pushed harder and blew the line. Changed the slave and the issue persisted. Then I yanked the trans, put it back in, and suddenly it worked. Yours has a push style slave like an LS, correct? How hard is it to bleed?

 

[OK93K1500]

It’s push style yes. I haven’t had a chance to try bleeding it. I know they come pre-filled and sealed, not to be bled- not sure if that speaks to whether they are easy. It’s just odd. Drove it tonight and it was fine. Went into several lots, backed up, went forward in low and also 1st, smooth as butter. Over about 2 hours I couldn’t get it to act up once. Until I got home and started maneuvering to get into the garage. Back to slamming, no slip at all. It was either engaged or not, no in between.

Haven’t owned a lot of manuals in my time I have to admit but I’ve never had one intermittently do something like this. There’s either an issue or there isn’t. A bearing has always either been bad or it’s not. Fork is either bent or broke or whatever, or it’s not. Hydraulics are either good or they’re not. Has me puzzled. I’ll have to find the time to yank it out.


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[Erik the Awful]

Your clutch release bearing slides back and forth on the input shaft bearing retainer. If the mechanic who replaced your clutch didn't grease it, it can hang up. Also, wear on the retainer can cause the bearing to hang up and not slide like it's supposed to - RockAuto has it for under $20. Either way, you're pulling the transmission.

 

[OK93K1500]

Your clutch release bearing slides back and forth on the input shaft bearing retainer. If the mechanic who replaced your clutch didn't grease it, it can hang up. Also, wear on the retainer can cause the bearing to hang up and not slide like it's supposed to - RockAuto has it for under $20. Either way, you're pulling the transmission.

Thanks! Last night I greased the fork ball/pivot using the zerk on the bell housing. Also greased the bushings for the clutch pedal. So far today it’s all been like butter, but it’s been intermittent all along so if it shows up again I’ll just bite the bullet and yank it. I’ll update accordingly, I always hate when questions and hard to pin down issues come up and they never get a final update!


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[OK93K1500]

Edit: Don’t know why my phone double posted. Sorry!

 

[OK93K1500]

Just an update for anyone coming along in the future, haven’t had a problem since, so that seems to have been the cure in my case!


1993 Chevrolet K1500 5.7/4L60E
1994 Chevrolet K1500 Heavy Half 5.7/NV4500

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