how do you like that dual disc?
i also have a 04.5 3500 SRW nv5600, been thinkin about the same setup, just wondering how smooth it is?
dont really know why im askin seening as i usually only use it to start, and float the rest of the time hahah
The dual disc is the only way to go for a work/tow rig...the performance single disc offerings, like the SBC OFe are too grabby and cause pretty rough jerking when trying to back up a load and they tend to grab pretty hard on takeoff. I had an OFe for a little while (about 35k before the pressure plate warped), and mine wasn't toooooo bad; but a friends was a harsh engagement no matter what.
The dual discs are seamless and smooth, just like OE; except they will hold regardless of load/horse power. I had one of the older offerings, and with the four levers...the rotating mass (the only thing that would make a difference in the speed of engagement) is the same between a diaphragm and lever versions...in other words, the comment about engagement speed was incorrect. The only thing the 3850 does over the 3250 is cause more clamping force and a little stiffer pedal, which the latter is alleviated by the use of upgraded (i.e. "12-valve") hydraulics. Again, mine was an older model, and it rattled...sounds like something is going to come out from under the truck when you push the clutch pedal in...but that was normal for them. They have made improvements to make them less noisy now from what I understand. There is no notable difference in shift speed between a OE and dual disc.
As far as twisting off input shafts...they make billets for the NV4500/NV5600 to prevent that. I was only running a Smarty JR on tow when I toasted the OE clutch...turned out I had a faulty OE clutch disc that was only touching in three spots about the size of a 50 cent piece. The funny part was I had 180k miles on that clutch disc without any issues, then toasted it within five minutes.
If anyone is interested: I still have the flywheel (surfaced once), OFe disc (looks new), and warped pressure plate; if someone wants to try installing a OFe disc with a stock pressure plate. Free, just pick it up near Reading, PA (weighs about 75#s, so shipping isn't going to work). On second thought...I better make sure I still have it.
For those running the NV5600...if the shifting becomes sticky or really notchy, change the fluid. I had to change the fluid (synchromesh) in mine about every 25k miles to keep the shifting feeling nice (to me).