NV4500 clutch problems

[woody80z28]

I swapped a NV4500 in my truck in 2011. Been a few years and lots of miles with no problems. The past few months it has given me some trouble. The pedal started to get harder. Didn't notice it at first cause it was gradual and I've got 3 other stick cars I drive. Master blew out so I replaced it. Slave blew out so I replaced it. Yesterday it feels like the slave blew out again (no pedal and no disengagement). I've got to get it in the garage and get a look.

What do you think could be causing some of these issues? Lately the pedal felt normal for about 3/4 of the throw and then really heavy the last 1/4. Needs the last 1/4 to shift in gear from a stop. I'm thinking maybe a fork problem? The pressure plate is heavy, but not crazy. It's a Napa "Heavy Duty" replacement that my buddy recommended who does a lot of towing. Always worked great for me towing too.

Just looking for some ideas on other things to check. Thanks

 

[Chewy1576]

I was having the same problem after swapping in my NV4500. It was a worn throwout bearing. When I had the transmission out, I replaced the fork, clutch, and pressure plate as well. The clutch pedal moves smooth as butter now.

 

[Blackwater]

I may can help with this. I have did a NV3500 MG5 swap to NV4500 MW3 using my TBI 350 in my C1500. I did make a mistake that I did not consider when I did my swap. First things first. What truck is the NV4500 is being transplanted into? Is the original engine being used and what is it? Which NV400 is it (MT8 or MW3)? lastly, what clutch are you using?

 

[woody80z28]

Not sure about the codes, but it's an external slave trans out of a 94 K3500. My truck is a 94 K1500. Original engine block, now rebuilt as a Vortec 357. I think it's this clutch, but I'd have to dig out an old receipt to be sure: https://www.napaonline.com/en/p/NCF1104902

 

[L29Sub]

Once the transmission is out, check the input shaft snout. The area where the throw out bearing slides can wear and cause what you describe. A few transmissions had aluminum snouts. If you find aluminum, swap it out for steel. Forget exactly what transmissions had the aluminum...? Worn steel causes the same issue.
The clutch pressure plate may be causing your problem. Also check the fork and pivot ball assembly. The ball will eventually cut through the release fork. Easy to replace once trans is removed. Use correct high temp lube on fork and throw out bearing snout as specified. Removing the snout is easy. Be sure the front trans seal is installed before assembling. And the slave cylinder could be galling up? Moisture settles out in vehicles that are not driven regularly.

 

[Chewy1576]

^^^^^

I'm fairly certain my input shaft is well worn and needs to be replaced now too. The bearings are probably shot also and the seal is leaking.


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[woody80z28]

Forgot to post back, it was the fork and pivot ball. Totally screwed. Ended up doing a whole clutch kit since it was only another $75 more than the throwout bearing only. Stock replacement 1ton clutch should be fine for what I need and it's way more wife friendly. The old Napa HD clutch was pretty heavy.

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[Blackwater]

That be the NV4500 MT8. I agree with the others. The old one looks bent.

 

[L29Sub]

The fork is bent, but it's related to the pivot ball wearing thru the fork and binding it up. Genuine GM forks are discontinued and becoming rare.
Common enough problem and may be the reason for going to rams head release.
Whereas the fork/ball bind thing allows a long failure curve, rams heads can just fail at any time without warning. Using cheap aftermarket clutch release parts is begging for a redo.
Two OEM parts that really dig into one's wallet are ramshead assemblies and GM late 454 mini starters...PG260?! Damn! My starter just quit. I stuck a PGMR on it and it works same as the 260, but no provision for the heat shield. Tube headers are going to cook that thing! Oh well...easy to replace....

 

[Blackwater]

Ok, If the fork components are becoming rare then in my personal opinion its time to swap to the internal slave cylinder. It actually a very simple but time consuming swap. GM went to the Internal slave cylinder in 1998 when the NV4500 MT8 was changed to the MW3. Differences are the slave cylinder and clutch change. Inside the gear ratios changed. you now have a 5.56 first and reverse gears. Now first and reverse are now synchronized. Other then that, they are the same. Hell I have a 2004 LQ4 bell housing attached to my 1993 5.7. Are they different? Yes and No. They kept the same 1958 bolt pattern but added an extra one at the top.

For you to swap to the internal slave, you need: Hydraulic line for the new slave. This one is shorter and flexible because instead of being on the passenger side it will now connect to the drivers side. Slave Cylinder with throw out bearing. A 1998 one ton clutch. You can use the original flywheel that came with your truck.

Remove the transmission. Remove clutch. Note: you cannot use the old clutch. the new one has a thinner pressure plate. Remove flywheel. Note: If it can be turned and stay within specs then that is $35 at the local machine shop. Remove pilot bearing/bushing. Note: This is always good practice. There are pullers for this that you can rent from your local Autozone or Orilliy's. Remove fluid from the Master cylinder. Note: This is important for the next step. Also, if you don't want brake fluid to eat your paint on the fender then have a catcher and a quick clean-up ready. Remove the pin that holds the hydraulic hose to the master cylinder. This is where catching fluid is important. Connect the new hose and replace the pin. Route the hose in a place where the exhaust or anything else will effect the hose. Install new polite bearing/bushing in the back of the crank. Install flywheel and torque to specs. Please do not use German torque specs. Install disc and pressure plate. Use alignment tool to alien disc by centering and pushing the tool up as far as you can. Install slave cylinder to the transmission. Stab the transmission. Torque bell housing bolts to specs. Install the rest of the components, cross member, shifter, transfer case (if 4x4) and drive shaft. replace any fluid lost in the tranny.