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Something Different, Swapping 6 for 5, 2 for 1
In a 3rd Gen Ram, ever thought of swapping an NV5600 for an NV4500? What about a top-of-the line dual disc clutch for a single disc unit?
KORE’s Hemi-powered Ram 2500 race truck uses blueprinted Blumenthal NV4500 five speeds and South Bend single disc clutches. After a bunch of successful races with this truck, we decided to take the next logical step and upgrade (that’s right, I said, “upgrade”) our CTD-powered Beast to the same transmission and clutch.
For years the Beast used a tried and true NV5600 and South Bend dual disc clutch. Bulletproof. Zero problems – ever – except when the transmission caught fire after I rolled the truck at the Parker 425 in 2005. It took four fire extinguishers to put it out. And that time when the Banks Sidewinder motor was in it, running propane, nitrous and a turbo too big to imagine…
Anyway, all hard core race, prerunning and towing duties were easily handled by the NV5600 and South Bend Dual Disc clutch. So why change?
Well, first of all, I hate the NV5600. It’s a heavy, cumbersome, Pigosaurus. When I bought the truck new in 2002 I thought, “She’ll shift better after she breaks in.” But she never did. To no avail I tried every trick synthetic lubricant on the market. Shifts were always rough and forced – as if the synchros were worn out. This was compounded by the fact that with a six speed transmission, you have to shift more often because the ratios are closer. This is fine for towing - but we only tow a 10,000 lb. trailer with a race truck on it. Pretty light by CTD standards.
Prerunning a race course off road in a big, properly-equipped diesel can be really fun, but not when it feels like a tow rig. A bunch of shifting for only 10 to 20 mph speed differentials is annoying. Another annoying thing is stabbing the throttle and waiting for the drive train to spool up. When I want to kick the truck sideways, I want the truck to respond immediately.
This leads me to MOI – Moment Of Inertia – friend and foe, depending on what you want it to do. Lots of MOI is good when you’re sled pulling and you don’t want your launch to be affected much by this thing called, “gravity.” Spin something heavy and it won’t slow down easily, spin something light and it will slow down quickly. Conversely the heavy object won’t speed up fast, but the light object will. This is your clutch and flywheel in action.
A heavy flywheel and clutch is great for towing. When the motor revs up, the clutch is released slowly then the truck accelerates slowly and without incident. The heavy flywheel spins, helping the motor turn circular momentum into forward motion.
But what about when you’re not towing? Like when you’re on off road, on a big, silty hill climb with a sharp turn in the middle of it? The hill is steep, you’re losing power and you need to down shift to make the turn – but if you down shift, you will lose your momentum and slow to a crawl before the shift is complete, then you’ll dig yourself a hole and never escape the hill. You can remain in the higher gear and hope that the heavy flywheel will keep the motor spinning without stalling – or, using your light weight Blumenthal wide-ratio five speed NV4500 you can leave it in gear, stab the throttle at the apex of the turn and power through with the tires spinning due to your trick, superlight South Bend flywheel and single disc clutch assembly.
This is simply a different way of doing things. It's great for off road because the drivetrain becomes much more responsive - and the NV4500 weighs a couple hundred pounds less than an NV5600. It's great for city driving because you don't have to shift as often. This would also be an excellent retrofit option to replace an automatic transmission. Better mileage, better mileage, better mileage.
The entire procedure is pretty simple. Without the cross member fabrication our team can do this in under two hours - in the field.
I drank a cold coke and took photos while our Crew Chief installed these parts. I thought I would share this with the TDR.
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