NV5600 issues/do I need a new clutch?

[Van-go]

Backstory…
My NV5600 was rebuilt (local shop Corey Transmission did a good job with that part)
I pulled transmission back in March of 2026 and got it back a week or so ago. Took a while to find a shop to rebuild…
I noticed the flywheel/clutch had become somewhat rusty but saw I still had decent life on my SBC dual disc. Decided to roll on with it.
Got everything buttoned up but truck was pulling full force with clutch all the way in. Wouldn’t go into gear from neutral with clutch pressed in. Narrowed it down to clutch being rusted together.
Started it in gear and got to 3rd or 4th (driving with clutch pedal fully pressed FYI)
Gave it the beans and clutch freed up from being seized.

Where I’m at now…
Clutch is slipping in pretty much every gear. Drove it back home in the grass in 4 low so it wouldn’t slip constantly.
Anyone ever had luck with getting one to grab again or should I go ahead and pull the transmission again and do the clutch?
Am I dumb to think it just needs to be cleaned like a brake rotor?

 

[Darkbloodmon]

Lucky of me to stumble on this post with my plethora of experience with this transmission and its issues.....

Figuring out the issue is hard to do without getting eyes on it(pulling it), by that point if the problem isn't staring you in the face during your inspection you'll have nothing but uncertainty if you put it back together. I'm speaking from experience as someone who's pulled my NV56 in my driveway 3 times with the help of friends chasing an issue that ultimately isn't resolved despite being drivable.

Before pulling it try checking the hydraulics for full travel, you can check the release fork for its travel by pulling the slave off and manually pushing the end of the fork, granted you won't get full travel but the point is to feel for binding on the portion that you can push. You can stick a bore scope through the hole where the slave mounts to and visually check the condition. If you want to parts cannon it before pulling, new hydraulics would be just about the only thing to throw at it until you pull it. Since you mentioned rust, the floater plate could be dragging in its slots and not re-seating on clutch release. Constant clutch actuation could help unstick it, if its the problem.

This excerpt on hydro testing is from South Bends "New" Website :

1. Check that the reservoir is full, and there are no leaks around the master cylinder on the firewall, or at the slave cylinder at the bellhousing.
2. On units with adjustable Master Cylinder rod (HYDX1.50 and HYDX.750) Make sure clutch pedal is 1/2"-3/4" above brake pedal.
3. If these two steps check out, before you remove the transmission, you can manually test the clutch with an "H" bar style steering wheel puller. If you do this with the truck running, make sure to block the tires, and all safety precautions are taken. DO NOT step on the clutch pedal with the slave cylinder removed.
4. Now remove the Slave Cylinder from the bell housing** and attach the steering wheel puller in its place. Using the threaded rod of the puller, tighten it by hand into the clutch release fork, where the slave cylinder rod would normally go. Tighten it as much as you can with your hand, then using a wrench turn the rod in 7/8ths of an inch and stop. With the truck running and the puller on, see if it shifts into gear. If it's working fine the hydraulics may need to be bled or possibly a new system needs to be installed. If the problem doesn't change or gets worse, then the transmission will have to be removed. A fluid change on the transmission could be in order.

** With the slave cylinder removed, make sure the clutch fork is able to move between the pressure plate and bellhousing 1/2in-3/4in. If the fork is pinned up against the bellhousing, or the free travel is more than the measurement provide then the transmission will have to be removed and clutch inspected.

If you have the means and the time to pull it and inspect it you might as well have a new clutch on standby ready to go in if you don't see anything glaringly wrong. Make sure the input shaft splines are clean and clear as well as the clutch disc splines. If you want to try reusing the south bend dual disc, I would clean the rust off the flywheel, floater, and pressure plate with a scotch brite on the mating surface and LIGHTLY scuff the disc's pucks with the scotch brite. Dust everything off and wipe it down the fly, floater and pressure with brake clean.

I say all this under the assumption that the transmission was rebuilt correctly.

My .02: if you like the South Bend Dual disk you have and haven't had any issues out of it; then stick with it. you got lucky. South bends dual disks for the NV5600 are notoriously crappy alongside their Koyo Clutch release bearings which are known for premature failure. If you need a clutch I'd recommend Valair, according to the people that have switched from a south bend dual disk to a valair they say its a night and day difference in noise, driveability and ease of operation. When I get the time I'm hoping to put my issues to rest with a Valair dual disk. I do not recommend south bend dual disc products for the Dodge/Ram Diesel Pickups. I had a South bend HD dual disc organic and it never shifted right, the plates dragged for the longest time on shifts and the rattle from the floater was terrible.

Hope this helps.

 

[Van-go]

Lucky of me to stumble on this post with my plethora of experience with this transmission and its issues.....

Figuring out the issue is hard to do without getting eyes on it(pulling it), by that point if the problem isn't staring you in the face during your inspection you'll have nothing but uncertainty if you put it back together. I'm speaking from experience as someone who's pulled my NV56 in my driveway 3 times with the help of friends chasing an issue that ultimately isn't resolved despite being drivable.

Before pulling it try checking the hydraulics for full travel, you can check the release fork for its travel by pulling the slave off and manually pushing the end of the fork, granted you won't get full travel but the point is to feel for binding on the portion that you can push. You can stick a bore scope through the hole where the slave mounts to and visually check the condition. If you want to parts cannon it before pulling, new hydraulics would be just about the only thing to throw at it until you pull it. Since you mentioned rust, the floater plate could be dragging in its slots and not re-seating on clutch release. Constant clutch actuation could help unstick it, if its the problem.

This excerpt on hydro testing is from South Bends "New" Website :

1. Check that the reservoir is full, and there are no leaks around the master cylinder on the firewall, or at the slave cylinder at the bellhousing.
2. On units with adjustable Master Cylinder rod (HYDX1.50 and HYDX.750) Make sure clutch pedal is 1/2"-3/4" above brake pedal.
3. If these two steps check out, before you remove the transmission, you can manually test the clutch with an "H" bar style steering wheel puller. If you do this with the truck running, make sure to block the tires, and all safety precautions are taken. DO NOT step on the clutch pedal with the slave cylinder removed.
4. Now remove the Slave Cylinder from the bell housing** and attach the steering wheel puller in its place. Using the threaded rod of the puller, tighten it by hand into the clutch release fork, where the slave cylinder rod would normally go. Tighten it as much as you can with your hand, then using a wrench turn the rod in 7/8ths of an inch and stop. With the truck running and the puller on, see if it shifts into gear. If it's working fine the hydraulics may need to be bled or possibly a new system needs to be installed. If the problem doesn't change or gets worse, then the transmission will have to be removed. A fluid change on the transmission could be in order.

** With the slave cylinder removed, make sure the clutch fork is able to move between the pressure plate and bellhousing 1/2in-3/4in. If the fork is pinned up against the bellhousing, or the free travel is more than the measurement provide then the transmission will have to be removed and clutch inspected.

If you have the means and the time to pull it and inspect it you might as well have a new clutch on standby ready to go in if you don't see anything glaringly wrong. Make sure the input shaft splines are clean and clear as well as the clutch disc splines. If you want to try reusing the south bend dual disc, I would clean the rust off the flywheel, floater, and pressure plate with a scotch brite on the mating surface and LIGHTLY scuff the disc's pucks with the scotch brite. Dust everything off and wipe it down the fly, floater and pressure with brake clean.

I say all this under the assumption that the transmission was rebuilt correctly.

My .02: if you like the South Bend Dual disk you have and haven't had any issues out of it; then stick with it. you got lucky. South bends dual disks for the NV5600 are notoriously crappy alongside their Koyo Clutch release bearings which are known for premature failure. If you need a clutch I'd recommend Valair, according to the people that have switched from a south bend dual disk to a valair they say its a night and day difference in noise, driveability and ease of operation. When I get the time I'm hoping to put my issues to rest with a Valair dual disk. I do not recommend south bend dual disc products for the Dodge/Ram Diesel Pickups. I had a South bend HD dual disc organic and it never shifted right, the plates dragged for the longest time on shifts and the rattle from the floater was terrible.

Hope this helps.

I appreciate the input. The 5600 shifts perfectly since I broke the clutch loose (it didn’t shift right before the rebuild/before i ran it out of oil) was pretty tough to shift out of 3rd gear lol
I don’t plan to keep truck forever so I ended up going a somewhat cheap route and opted to have SBC refurb my clutch.
Hopefully I don’t have any issues with it, now I’m nervous

Figured if I’m going to pull it out again, I might as well have a new clutch sitting there to throw in.

 

[Shreddinlettuce]

I appreciate the input. The 5600 shifts perfectly since I broke the clutch loose (it didn’t shift right before the rebuild/before i ran it out of oil) was pretty tough to shift out of 3rd gear lol
I don’t plan to keep truck forever so I ended up going a somewhat cheap route and opted to have SBC refurb my clutch.
Hopefully I don’t have any issues with it, now I’m nervous

Figured if I’m going to pull it out again, I might as well have a new clutch sitting there to throw in.

Does it have a pressure plate with ramped plastic wedges (self adjusting) those can ratchet down too early causing problems

 

[Shreddinlettuce]

Most clutches are rebranded from 3 of 4 manufacturers

 

[Darkbloodmon]

Does it have a pressure plate with ramped plastic wedges (self adjusting) those can ratchet down too early causing problems

Not on a south bend dual disk unit, the technical design is pretty archaic. There current dual disks use a different design for the floater plate. Currently the "ears" have a plastic cap on them that slots into a provision on the fly wheel with a dowel pin aligning it and dampening the oscillation.

Previously their dual disk floater plates were aligned with a dowel from the flywheel and the fly wheel had plastic bumpers where the "ears" of the floater could move back and forth oscillating with the engine speed.

 

[Darkbloodmon]

I appreciate the input. The 5600 shifts perfectly since I broke the clutch loose (it didn’t shift right before the rebuild/before i ran it out of oil) was pretty tough to shift out of 3rd gear lol
I don’t plan to keep truck forever so I ended up going a somewhat cheap route and opted to have SBC refurb my clutch.
Hopefully I don’t have any issues with it, now I’m nervous

Figured if I’m going to pull it out again, I might as well have a new clutch sitting there to throw in.

Hoping for the best with it. Do you over fill the trans fluid? It helps with the shifting and the rear end bearing lubrication.

The trans fluid can be hit or miss, some units like a certain type over others depending on wear and tear and it can significantly affect the shifting, even more with a dual disk with the additional moving components.

 

[Van-go]

Hoping for the best with it. Do you over fill the trans fluid? It helps with the shifting and the rear end bearing lubrication.

The trans fluid can be hit or miss, some units like a certain type over others depending on wear and tear and it can significantly affect the shifting, even more with a dual disk with the additional moving components.

I put in 7 quarts of amsoil syncromesh.
When I drained it before rebuild it had about one quart of super sparkle mystery fluid. Hahaha

 

[Darkbloodmon]

I put in 7 quarts of amsoil syncromesh.
When I drained it before rebuild it had about one quart of super sparkle mystery fluid. Hahaha

That'll do it, Take everything below with a grain of salt if your transmission was working fine the way you had it filled.

I'm looking through my notes with a calculator. 7 quarts(US) is 14 pints(US). That's too much fluid and could cause some shifting issues.

Factory fill(without coolers) is 9.5 pints or 4.75 quarts, add a one quart over fill for 5.75 quarts or 11.5pints

I use dual trans coolers on my case that add a combined 1 quart fluid capacity. 5.75 is my factory specified fill with the coolers. I do an over fill quart brining me up to 6.75 quarts or 13.5 pints.

7 quarts assuming you don't have coolers is too much.

On my first rebuild from Standard Transmission and Gear in Forth Worth Texas, they mistakenly instructed the diesel shop who re-installed it to over fill it to 9 quarts, and it could barely shift. I drove 70% of the way from Charlotte NC too Fort Worth TX in 6th gear for them to warranty it out and rebuild it.

I'm not planning on any major failures, but if I do get some glitter I'll probably save it for powder-coating the rebuild with some flake.

 

[jeepinmatt]

I put in 7 quarts of amsoil syncromesh.
When I drained it before rebuild it had about one quart of super sparkle mystery fluid. Hahaha

That's like the only fluid note expensive than Amsoil.

 

[Noel]

You probably just need to get a couple jacks and put a clutch in it. I got a trans jack at the house if you wanna borrow it @Van-go

 

[Van-go]

That'll do it, Take everything below with a grain of salt if your transmission was working fine the way you had it filled.

I'm looking through my notes with a calculator. 7 quarts(US) is 14 pints(US). That's too much fluid and could cause some shifting issues.

Factory fill(without coolers) is 9.5 pints or 4.75 quarts, add a one quart over fill for 5.75 quarts or 11.5pints

I use dual trans coolers on my case that add a combined 1 quart fluid capacity. 5.75 is my factory specified fill with the coolers. I do an over fill quart brining me up to 6.75 quarts or 13.5 pints.

7 quarts assuming you don't have coolers is too much.

On my first rebuild from Standard Transmission and Gear in Forth Worth Texas, they mistakenly instructed the diesel shop who re-installed it to over fill it to 9 quarts, and it could barely shift. I drove 70% of the way from Charlotte NC too Fort Worth TX in 6th gear for them to warranty it out and rebuild it.

I'm not planning on any major failures, but if I do get some glitter I'll probably save it for powder-coating the rebuild with some flake.

Shop that rebuilt it said to over fill with 2 extra quarts. I can siphon some out if needed I guess

 

[Van-go]

You probably just need to get a couple jacks and put a clutch in it. I got a trans jack at the house if you wanna borrow it @Van-go

Hahahaha come hang out. And you can use your jack I stole this afternoon.