Hard Shifting NV5600 Help Needed

S

SixSpeed5

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Joined
Sep 30, 2014
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Hey Guys, bare with me as this is going to be a little long winded, but I have been through quite the process to get where I am.

Background:
2003 Ram 3500 QC/LB DRW 4x4 NV5600
Current Miles: 265000

Horsepower - EST 650RWHP

User Experience: I am a heavy truck mechanic, and very well versed in manual transmission driving.

I bought the truck with 170K miles on the clock, it had a semi-recently rebuilt transmission with unknown mileage and a Sachs clutch.

I got to 260K miles with the Sachs clutch before it started to get weak. It really held up impressively well given the horsepower (Was only able to run Smarty at #5) and heavy towing. At almost the same time part of the shifting mechanism for 4th gear decided to fail. I had always run Redline MTL in my transmission with great results, old transmission was very clean and in good shape when it was disassembled.

I decided to bite the bullet and buy a rebuilt transmission, transfer case, and a South Bend DD-3250-6. At a little over $5000, it was a little (okay a LOT) painful, but I was really hoping I would have smooth sailing for a long time to come.

Transmission came from a local manual-only rebuilder who has been in business several decades, with a great BBB record, and good reviews.

I took the truck to only of the only local shops in town I trust my vehicles with, I am VERY particular about mechanic work. $600 later I had my truck back.

Oil used: AMSOIL Syncromesh

I immediately noticed difficulty in shifting. Not so much a notchy transmission, but more so it just not wanting to go into gear. I figured it was a new transmission, and a new clutch so I would give it a little time. About 200 miles went by and nothing had changed. I had contacted Southbend and they suggested I test the clutch hydraulics. The hydraulics on the truck were only about 8 months old, and was a SBC upgrade. The test showed no real change in shifting effort. One thing I had noticed, is that if you were at a light and it went green, got the clutch in and went for first it would not only resist for a second or two before going into gear, but the truck would roll about 8" or so forward while trying to get into gear and sometimes it would flat out not let you in gear without a considerable amount of force. Both upshifting and downshifting needed to be within ~200rpm to get into gear. Not a great sign. I have 40 year old truck transmissions that shift way nicer than this did.

Going to 350 miles on the new setup and while talking with SBC, they very kindly agreed to send me another clutch assembly.

I took apart the truck myself this time, and I confirmed everything was well installed. The clutch that came out had some funny wear on one disk, which SBC called "questionable" but as I said they graciously sent me another clutch. During this time I had been talking with the transmission rebuilder. I installed the new clutch EXTREMELY carefully and made sure everything was perfect.

Not a whole lot changed, I would say it was 10-15% better but I still wasn't near happy with it. At this point I decided to put some miles on it and see what happens as I didn't see a lot of options. Around 1500 miles on the transmission and 1200 miles on the clutch, the transmission randomly decided it was no longer willing to go into 1st gear without considerable grinding and a big thunk. All other gears remained the same. Something let go in the transmission? Probably something relating to the 1st gear syncro. It will be opened up on Monday or Tuesday.

After talking with the rebuilder, who has been very helpful and sympathetic through the process, they gave me a whole new rebuilt transmission (was actually my old NV5600 rebuilt) to swap out.

I completed that job today, which was as always a lot of fun. I believe I need a few trips to the chiropractor at this point. I inspected everything I could while I was in there, and all seemed pretty normal. I did NOT however separate the pressure plate from the flywheel since getting that dual disk aligned in a lot of "fun". The results were the same as they has been. Difficult to shift, rolling while trying to get into gear, high resistance sometimes etc etc.

I went back to Redline MTL this time around. With no change I went for my last resort, which was installing a brand new set of SBC hydraulics. No change in shifting behavior whatsoever. Plenty of experienced mechanic friends had driven the truck through the process and agreed it is not right, I'm not just being pedantic.

At this point I am very disappointed. Two clutches, two transmissions, two sets of hydraulics and a TON of downtime, time, money and effort lost. I depend on this truck every day for transportation, and for work so the downtime has been terrible for me. I am out of time, out of money, and out of patience. I am scared to use the truck and hurt another new transmission.

My question to the community is what do you think I should do next?

Has anyone installed a SBC dual disk unit and been extremely disappointed with the results?

I know DD clutches are going to shift a little slower due to the mass of two disks, but what I have is excessive and I believe to be harming the transmission.

I genuinely think the only thing I can try is going back to a single disk, but I don't have the money, don't have the time, and don't want the aggressive engagement!

Any help would be hugely appreciated. Thank you for your time if you made it this far! :P
 
Anytime I have had a tranny issue with hard shifting always seemed to follow after getting a rebuilt nv5600. Tons of sbc dd clutches and not one issue with not going into gear. Little slower yes but no issue of going into gear.
 
My 02 is a bit hard to get in gear, but not at all as you describe, and that is with a South Bend DD and a fresh rebuild on the NV5600. My 03 with a Valair DD is very, very easy to get in, but it also has at least 110k on the tranny. Do you have a short shift kit on the truck? I have found that they will make shifting harder, but not to the point you describe.

How does it feel shift wise with the truck off and the clutch engaged? Smooth and easy or still difficult? Where does the clutch engage at? Towards the bottom of pedal travel or somewhere else?

It sounds like you do have not enough travel in the clutch operating fork, do you still have the spacer between the tranny and the slave?

The only other things I can think of is that when you received the tranny, you might have been given the wrong clutch fork that is not locating the throwout bearing correctly (to far rearward) thereby not giving you full clutch disengagement. I rate this as very unlikely, but possible. I don't think a 4500 fork will work in there?

You definitely are not getting enough clutch disengagement.
 
RDPsmoker said:
Anytime I have had a tranny issue with hard shifting always seemed to follow after getting a rebuilt nv5600. Tons of sbc dd clutches and not one issue with not going into gear. Little slower yes but no issue of going into gear.
Click to expand...

I suppose it is a bit comforting knowing that you have had good luck with clutches. I feel like a little slower would be okay, but I feel like I would be really shortening the lift of the syncros with what I have now.


Billysgoat said:
My 02 is a bit hard to get in gear, but not at all as you describe, and that is with a South Bend DD and a fresh rebuild on the NV5600. My 03 with a Valair DD is very, very easy to get in, but it also has at least 110k on the tranny. Do you have a short shift kit on the truck? I have found that they will make shifting harder, but not to the point you describe.

How does it feel shift wise with the truck off and the clutch engaged? Smooth and easy or still difficult? Where does the clutch engage at? Towards the bottom of pedal travel or somewhere else?

It sounds like you do have not enough travel in the clutch operating fork, do you still have the spacer between the tranny and the slave?

The only other things I can think of is that when you received the tranny, you might have been given the wrong clutch fork that is not locating the throwout bearing correctly (to far rearward) thereby not giving you full clutch disengagement. I rate this as very unlikely, but possible. I don't think a 4500 fork will work in there?

You definitely are not getting enough clutch disengagement.
Click to expand...

No short shift kit on the truck, I don't mind rowing :)

With the truck off and the clutch pedal in it feels pretty good, a little snug but what I would expect out of a fresh transmission. Do you want me to check it with the clutch pedal out (engaged)?

I have the pedal adjusted about as far out as I am comfortable, truck starts wanting to move about 4 inches off the floor. Started adjusting from about 2 inches from the floor and didn't change shifting effort.

There isn't a spacer between the transmission and the slave cylinder, and the washer behind the pivot ball on the transmission was removed. When the second SBC clutch went in, a new fork & TOB went in as well. I put in a whole new kit from SBC both times.
 
I just got finished installing a valair dd in mine today. Almost 100mi on it so far and shift effort is just slightly more than stock. Oe replacement hydros appx 8 months old. Is it all gear ranges that are hard to get into or just 1 gate?
 
Did you check the pilot bearing when swapped the clutch? Possibility it could have been damaged when the shop did the initial install. I had the same issues with a single disk. Worked great for the first 10k miles. Then started having trouble with first and reverse that got progressively worse to the point I was having to turn the truck off to get it in reverse. Then out of nowhere it all went to working right again. Pulled the tranny and the pilot bearing was disintegrated. Everything else was fine. I guess it was causing some drag on the input shaft till it completely came apart, then no drag.

Sent from my XT1254 using Tapatalk
 
I have found that an NV5600 is a "notchy" shifting tranny, but gets much worse with dual disc set-ups.
Overall, dual discs add weight to the input shaft, which is harder to slow and the NV5600 does not have the greatest stop rings in the world, in the first place.
Personally, I steer clear of dual discs for the exact problems you are having.

Part of your first post alludes to the fact that the clutch is not fully dis-engaging, or is still spinning when you try to shift.

Another part of your post says that you can't get it into gear from a dead stop, that the truck will actually MOVE before it goes into gear.
This points to the clutch not disengaging.

I'd look at the hydros not fully disengaging, BUT in the end it'll likely come down to the fact that the stop rings aren't up to the task of slowing that much more weight down.

One test you can do is "dump truck shifts", which is no more than disengage the clutch, shift out of gear, pause for a bit, then shift into the next gear.
If this improves the shift, there's excessive gear speed that diminishes as you wait.
If it still "binds", or goes in hard, the clutch is physically not disengaging fully.

If it didn't have stop rigs, you'd be grinding every gear.

The G-56 shifts quite well with dual discs, but it was designed for them.

Mark.
 
May need to install a longer pushrod for the slave cylinder. I usually buy a couple of bolts at different lengths, grind them down to the length I want and do a trial and error run.

Pretty much every dual disc I've used, I've had to do this to because I had similar issues as you mentioned. Made some longer pushrods, stuck them in and now they shift great.
 
6.6lEater said:
Is it all gear ranges that are hard to get into or just 1 gate?
Click to expand...

All gear ranges are difficult. I forgot to mention that every once in a while it will really hang up. Went to church this morning and while trying to pay it didn't want to let me in reverse, then didn't let me in 2nd, I could have used all the force I had and it wouldn't have gone in. Probably would have broken something if I tried any harder. Went back into first, then it let me in 2nd.

homewrecker said:
Did you check the pilot bearing when swapped the clutch?
Click to expand...

Yeah, on the second clutch install it got a new flywheel and a new pilot bearing. On the second rebuilt transmission the pilot bearing was inspected and seemed good.

Mark Nixon said:
One test you can do is "dump truck shifts", which is no more than disengage the clutch, shift out of gear, pause for a bit, then shift into the next gear.
If this improves the shift, there's excessive gear speed that diminishes as you wait.
If it still "binds", or goes in hard, the clutch is physically not disengaging fully.
Click to expand...

If I double clutch properly, ie matching RPMs near perfectly, it goes in and out of gear just fine downshifting and upshifting. Unfortunately it doesn't help me getting into gear from a standstill. That and I would just as soon burn this thing to the ground then double clutch everywhere. But that is what I have been doing since I put the second reman. transmission in.

weazel said:
May need to install a longer pushrod for the slave cylinder. I usually buy a couple of bolts at different lengths, grind them down to the length I want and do a trial and error run.
Click to expand...

Haven't heard of this before, how much have you had to extend them on average?
 
SixSpeed5 said:
Haven't heard of this before, how much have you had to extend them on average?
Click to expand...

Around 1/4 inch or so. I usually start a hair bit long and grind down to right where I like the pedal position and where it releases.
 
SixSpeed5 said:
Haven't heard of this before, how much have you had to extend them on average?
Click to expand...

Around a 1/4 inch or so. I usually start out a hair long (1/2") and start grinding it down till I find that spot I like where it releases and the pedal position is where I like it
 
weazel said:
Around a 1/4 inch or so. I usually start out a hair long (1/2") and start grinding it down till I find that spot I like where it releases and the pedal position is where I like it
Click to expand...

I guess I could try it, I don't have much to lose at this point. How did you determine at what point the clutch was disengaging?
 
I'd take the original rod and find a bolt approximately the same diameter. The hex side of the bolt just grind it to a round shape to fit in the shift fork decently.

On the threaded side of the bolt, just knock the threads down to make it a little on the smoother side. I'd make the bolt about a 1/4" longer than the original shaft with the plastic tip on it.

When you get the newly made rod in there, try to shift into 1st. If it works, it should slide right in. If it is good to go, shifting will be way easier.

If it doesn't work, but feels like it's really close, make another bolt a little bit longer than the other.

Also, if it releases too high on the pedal for your liking, grind the bolt down an 1/8" and go from there.

If this doesn't solve the problem, which I'm pretty sure it will, then there may be some issues going on in your trans...
 
Some places sell a bare, un-threaded rod for making your own all-thread and it is usually stocked along with the all-thread.
I've used this to make the pushrod and it works just fine.

Keep in mind that while the theory of a longer pushrod is a seemingly good one, the very nature of hydro clutch cylinders means that all you're doing is transferring the stroke, you're not really "increasing" anything, just placing it to where it works more efficiently.

A longer pushrod puts the slave's piston shallower in the bore, slightly decreasing the fluid volume on the slave end.
An adjustable master pushrod (some of SBC's slave/master kits have them) is also a remedy and works similarly.

Mark.
 
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