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Hard Shifting NV4500, less than 2 years on clutch

And when You go to the parts store for the new slave cylinder, stand on the parts counter persons head, until they fully understand that they are looking up that part for a diesel.
Might be best to check with the transmission shop for a slave cylinder, or even a clutch rebuilder shop.
They should know better than anyone what it takes for this clutching system..
 
New slave is in and no real difference. The master was replaced in late 2017/ early 2018, I guess I could replace that too as the last piece of the chain as per @Husker6.5 's suggestion. If that doesn't fix it then I'll have to take to the experts. Will overfill by 1 quart when the fluid arrives on Monday but that feels like wishful thinking at this point. Bellhousing was solid when I had it out and I can see the slave is lined up with the clutch fork through the inspection hole.

Transmission came from High Gear out of Memphis, TN. They use cores as I believe production of the NV4500 ended around 2007, but it's all new internals and cryogenic treated to boot.

Also FYI for anyone doing a transmission swap/ upgrade: The bellhousing bolt pattern (of trans to bellhousing) for '93-'95 GM NV4500s is different than '96+. Don't know if that was to accommodate for the external slave cylinder or just more infinite wisdom from the geniuses at GM

@Twisted Steel Performance is the master w/ adjustable rod a custom creation of yours or an aftermarket upgrade?

Also may be a silly question, but for the cap of the master cylinder, do you want the bladder type thing inside the cap to be squished in when putting on the cap or sticking out all the way? Or does it not matter
 
DieselAmateur said:
New slave is in and no real difference. The master was replaced in late 2017/ early 2018, I guess I could replace that too as the last piece of the chain as per @Husker6.5 's suggestion. If that doesn't fix it then I'll have to take to the experts. Will overfill by 1 quart when the fluid arrives on Monday but that feels like wishful thinking at this point. Bellhousing was solid when I had it out and I can see the slave is lined up with the clutch fork through the inspection hole.

Transmission came from High Gear out of Memphis, TN. They use cores as I believe production of the NV4500 ended around 2007, but it's all new internals and cryogenic treated to boot.

Also FYI for anyone doing a transmission swap/ upgrade: The bellhousing bolt pattern (of trans to bellhousing) for '93-'95 GM NV4500s is different than '96+. Don't know if that was to accommodate for the external slave cylinder or just more infinite wisdom from the geniuses at GM

@Twisted Steel Performance is the master w/ adjustable rod a custom creation of yours or an aftermarket upgrade?

Also may be a silly question, but for the cap of the master cylinder, do you want the bladder type thing inside the cap to be squished in when putting on the cap or sticking out all the way? Or does it not matter
Click to expand...
There are a lot of places that do free diagnostics and estimates.

Its often worth a trip for an educated guess.

If the price is right, I have them do the work. Anymore, I most often have them do the work. But I may check more than one shop.

I still hate having shops work on stuff. The extra stuff I would do never gets done - but as evidenced by the Tahoe - nothing ever gets done here anymore.
 
New master cylinder went in this evening...and it's no different. If anything it's worse! I didn't think the master would be the problem and this shows it wasn't. I have now replaced everything in the clutch and transmission system, with the exception being the clutch line, which was also new with the previous master in late 2017/ early 2018 so I don't think there's an issue there.

Also overfilled by 1 quart with OEM fluid and of course it didn't make a difference.

The hard shifting happened a week or so before swapping transmissions. When I pulled the bellhousing and saw the fork pivot ball stud was snapped off, I figured this was the reason the clutch wasn't fully disengaging. However with everything else replaced this issue hasn't gone away.

The only 2 things that are different from when the clutch was previously working fine are:

1) the long snout pilot bearing

2) the adjustable throw- out bearing

I'm suspicious of the throw out bearing for the following reason: When I adjusted and set the bearing, there were extra threads sticking past the bearing face. I called the folks at Novak and asked about this feature and was told that this shouldn't interfere with the clutch.

here is the stock bearing on left that came with the south bend clutch kit, Novak adjustable bearing set to spec on the right

IMG_0938.JPG


Does anyone think this could be getting in the way of the clutch fully disengaging?

Is there any way the long snout pilot bushing could be interfering at all?

I know for a fact the slave cylinder moves, I can see it through the inspection hole in the bellhousing when I block the clutch pedal with a piece of wood. I don't think it's moving as far as it can though, as I don't see the fluid in the master cylinder drop too much and clearly something is stopping the clutch from fully disengaging.

@Twisted Steel Performance, I know your bearing was adjusted even larger than mine, but did you have any exposed threads like my bearing does?

Everything possible has been loaded and fired in the parts cannon with no change in result, so I don't know what else it could be aside from something already present in the system. Thoughts?
 
I'm still leaning towards an internal issue with the transmission with either shift rails/forks or with the linkage. How are the bushings on the shifter shafts? Any binding? With the TO bearing on the right, it should make the fingers on the clutch move even further away to release when the fork moves forward. A "new" reman doesn't necessarily mean everything is right internally with the core they started with or the new parts they used.
 
I'll reach out to High Gear about the transmission, they allegedly dyno test all transmissions according to their website...

And the protruding threads from the adjustable bearing don't hit the pressure plate fingers, they are smaller in diameter than the opening and go past/ through the fingers. I don't hear any rubbing/ grinding/ binding when stepping on the clutch. The clutch sifts fine with the truck off, and shifts slightly better while driving, but when moving it tonight I had to literally shut the truck off and put it in 2nd after being in reverse as I couldn't shift with the engine running
 
No, I wasn't commenting on the protruding threads hitting anything, I know they fit inside the circle of the clutch fingers. I was commenting on the position of the TO bearing face itself being further forward than the South Bend bearing, and how that will give you more release for the same travel of the clutch fork. It does not sound like you have a clutch release issue, it sounds like you have an internal transmission mechanical issue causing your shifting issues. And, dyno testing before it goes out the door doesn't mean diddley if something goes wrong after it's been installed and used in the real world shortly thereafter. Jasper claims to dyno test their automatic transmissions before they ship, but I still wouldn't put one in a vehicle I intend to keep. Same with their motors. Just saying, something that passes before shipping doesn't mean it will last after install and use for a bit. JMHO.
 
Fork is brand new too. Literally everything is new.

@Husker6.5 I appreciate your perspective on the transmission itself being the issue, any outside opinion is helpful with this issue. The folks at High Gear have already emailed me back so at least their customer service is ok

One thing High Gear recommended that I didn't think of is the flywheel. That wasn't replaced and could be original to the truck as far as I know. I have no frame of reference for how to check whether a flywheel is "good" or needs resurfacing/ replacing. If anything, I thought a worn flywheel would prevent full engagement of the clutch, not prevent disengagement?

The only reason I'm reluctant to throw in an adjustable rod is I've already spent way more than anticipated and nothing is resolved. I've had fine results in the past with the stock master, rod, t/o bearing etc, so I'm not sold that one upgraded stock item is the solution yet.

I'm still skeptical of the new/ different parts, specifically t/o bearing and possibly pilot bushing. Anyone have an opinion on whether a worn flywheel could be part of the problem here too?
 
I doubt its a shift fork issue, the NV4500 was not know for those issues. The only time I have seen one develop an issue was on a trans I rebuilt or my buddy's dodge. It sat for 6 years after I rebuilt it. Once He got it up and running for his son it would have issues down shifting after going into 5th. But would Up shift with no issues all the way through the gears. I found I could get it out of 5th gear but the sticking 5th gear fork would keep it engaged just enough to cause it to lock out the rest of the gears. After a few weeks it worked its self out and has been fine. Must have gotten surface rust from sitting.

And for what's its worth we have installed 100s of jasper Engines and Transmissions and only had one give us a problem. It had a bad lifter tick when it got hot so the dyno had no chance to catch that one. They had a new engine to me next week and payed me to install it. Id install a jasper reman in anything without hesitation.

The only time I've seen a flywheel casus a release issue is if its been machined and did not get properly shimmed back to the proper location on installation.

This sounds like a hydraulic issues to me. I usually bench bleed the master and slave together then install it in the truck. That seems to be the only way it get all the air out. Even a pressure bleeder doesn't work on this system. Now that I think about it the last GMT400 clutch issue I had ended up being the pedal its self. It was so worn out it wouldn't push the rod in enough. I ended up getting a complete assembly from the junk yard.
 
I agree it sounds like a hydraulic issue, but I don't know what else to do about it. I'll crawl under and bleed the slave again tomorrow for funsies but it's starting to feel like insanity doing the same thing and expecting a different result. Maybe I'll load up one more thing for the parts cannon and get a stainless braided line and pull master and slave and bench bleed.

FWIW the owner at High Gear thinks it's the flywheel. I really don't want to go through it all again but with my luck it probably is literally the last piece in the chain. Wasn't budgeting for a $700 south bend clutch kit and with the credit card maxed out the extra $320 for the flywheel didn't seem worth it at the time. Of course gotta learn the hard way to do flywheel when doing clutch especially when health/ age of flywheel is unknown.

I know I've already mentioned it, but no one thinks the extra threads protruding from the adjustable throw out bearing are a potential problem? As already stated I can see the slave travel when looking through the inspection hole in the bellhousing. Can't see the end of the slave hitting the fork with pedal all the way up, and when blocking pedal all the way to the ground I can see the end of the slave pressed into the dimple on the fork. So the fork is moving, just doesn't seem to be enough, even with the bearing adjusted 1/4" longer than stock. And I'm wondering if the threads are stopping full travel of the slave, causing my issue.

Is there any other symptoms I can look for that would indicate a worn/ concave flywheel? Noise, vibrations, etc?

thanks for everyone's input on this, it's quite maddening and I sincerely appreciate everyone taking the time to chime in
 
Its hard to diagnose something like this without feeling the pedal for myself. All I can suggest is to bench bleed the clutch system and see if that works. Ive had to do that to just about every hydralic clutch system I've ever repaired. A pressure bleeder does a good job on most, same goes for back filling. But the GMs always give me issues.
 
@Rockabillyrat when done bench bleeding what do you use to hold the slave in place (keep rod from fully extending) while handling and installing the clutch hydraulic system? I've heard that letting the slave extend too far out can let air into the system, and of course I probably lost in the mess of my shop the little plastic strap that came with the new slave
 
I've never had an issue installing them into the truck without the strap of anything else holding it in place. When bench bleeding it though you need to strap it with something when you pump it. A large zip tie will do the job if you want to hold it.
 
DieselAmateur said:
I'll reach out to High Gear about the transmission, they allegedly dyno test all transmissions according to their website...

And the protruding threads from the adjustable bearing don't hit the pressure plate fingers, they are smaller in diameter than the opening and go past/ through the fingers. I don't hear any rubbing/ grinding/ binding when stepping on the clutch. The clutch sifts fine with the truck off, and shifts slightly better while driving, but when moving it tonight I had to literally shut the truck off and put it in 2nd after being in reverse as I couldn't shift with the engine running
Click to expand...
What is it doing? Is it not disengaging? Is it grinding when ypu try to shift?

Is thete a way to verify the throw out bearing is moving the proper amount?

I have only had to change a few clutches or clutch parts.

The biggest issue I ever had wad bleeding the clutch.
 
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