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

 

talk about brutal.

is there still any possibility its something internal? i know its rebuilt.. but it almost sounds like a synchro is still not working properly. did you try doing a flush to see if any buildup or metal shavings came out in the fluid.. it almost sounds as if its binding internally and not so much clutch related..

its a long shot.. but i know with for example my volkswagen when you change the clutch etc its reccomended to realign the shift fork on the trans.. now im not 100% familiar with the trans in these yet.. but.. im wondering if you maybe need to adjust the shifter linkage for the shifter itself and this could be causing it to resist going into gear and not be an internal issue at all?

sorry im not much more of a help just thought id pitch in anything relevant i could think of.

 

was the sacs clutch a dd or a single the dd shift slower

I have not been into the 5600 so I could be off on this

on the 4500 you can take the top off and shift it manually with a bar make sure it works easy in all directions if it does then it might be in your shifter assembly

just a thought

 

My truck was down for three months while I rebuilt the NV5600. Not putting down the power you are, 400-450hp. After the rebuild which I did, I can barely shift the thing. I was a heavy equipment mechanic and too am confident in doing this type of work. I pull a heavy horse trailer (20,000lbs) and thought that was the problem when it broke and locked up in two gears. Luckily it broke in the driveway backing up to the trailer. My single disc clutch (carbon/kevlar) clutch was just about done and because it was so grabby I went with the SB dual disc. I flat out love this clutch, it's butter smooth. I already had the HD hydraulics and now my wife can drive the truck again, except she can't shift it, and neither can I. So back to the rebuild. It locked up because the original syncro's had 1/8" holes right below the tab. That's where they broke, in several pieces and wadded up on one side of the sycro gear effectively locking that gear up. The new syncro's didn't have the hole, and the tabs were slightly wider. Also... about half of the little springs under the ***** were broke when I took it apart. I didn't have a way of checking it, but I believe the new springs are stronger than the old ones I took out. The wire diameter looked bigger but I didn't have any way to measure it, nor did I really care at the time. I know when I tried to shift the slider by hand it was nearly impossible. I think that is the problem. That whole spring, ball and gear piece is a stupid design. I don't know what I'm going to do if I can't fix the shifting issue economically. I don't want to pull that tranny out again, that was a lot of work, and down time. I'm thinking at this point if I pull it out again I'd like to install the new Eaton Procision Dual-Clutch 7-speed transmission, which isn't for sale yet, it's that new. Ref: (Procision Dual-Clutch Transmission)

 

I'd pull it and rebuild it if any fluid other than the dodge or gm brand specific oil for these nv's are used the tranny goes to ****