Been wanting to do this for a long time and finally did.  Basically its my truck with 245/75/16 Tires and 3.54 rear with Nv4500 Vs Nv5600.

 

The chart shows me shifting at 2000RPM in every gear then picking up the next gear at the same MPH that the last gear was going at 2000RPM.  The numbers between show the RPM drop between gears, as in 4th to 5th on the Nv4500 drops 500RPM.  

 

Its interesting because the 3rd to 4th gap on the Nv4500 is actually less of a jump than 2nd the 3rd, but because it is still jumping a vast RPM at a higher speed, the truck can't cope with the lower RPM and high load of high speed that it encounters, so it "feels" like a huge gap.  When you compare it to the Nv5600, it definitely is a big gap.  From 15-50 there is exactly 2 gears worth on the Nv4500 and exactly 3 on the Nv5600.  Quite a difference.  However, I am not sure but based on the chart do you guys with Nv5600's feel a slight "gap" between 5th and 6th?

 

 

"felt"  is  a good term...    at least with  my   bone stock  cummins.        But,   I've been driving this  00   for  10 years too.        Now  that  I think I have  the   'feel'  for this  truck,  both  overloaded and  empty,   I'd say  it's  about  perfect for the way   IT HAS TAUGHT ME HOW TO DRIVE IT.  

 

My first experience  with  a  diesel pickup  was   a   1996  dodge 5 speed,   I  guess  at the time  I didn't  'dread'  or despise  the  transmission,  I just learned to   operate the vehicle  so   it wasn't     dogging it..   When the 2000 came along,    I found quickly  that  the cummins  didn't have to be  pushed quite as hard to   progress through the gears.. without much  thought.  but  that is  ME.   Others will  have different  results!!   

If the  od is used as  a  gear  'after  acceleration is  done'   then  the  'jump'  isn't  nearly as noticeable.      But,  put a guy or gal  behind the exact same truck  and  if they  short shift  into od  whilst still   going up a hill,  loaded,  into a nasty head wind..  and  they'll  cuss the very transmission as being   'way to  wide'.

As for me,    I got the  nv5600  almost ready to  put into the  97.        I don't  hate the   4500,  but  I am  spoiled  by the  first  5 gears of the  5600!

After having both……………..I like the NV5600 better for towing by far.  Empty, it doesn't matter.

I have liked my 6 speed since day one and 6th gear always just felt like another gear to me, though I try to run it at no more than 50% throttle with the 5th wheel on(15k #). The only experience I have with the 5 speed was on my 96 with the V10. It would only pull my other 5th wheel(12k #)on dead flat ground in 5th and I hardly ever used it while towing. Not sure that s a fair comparison. 5th on the gasser always felt like an OD, where as on the Cummins 6th just feels like another gear to me.

Edited January 13, 201411 yr by dripley

There are times with I want the NV5600 6th to be a .85:1 and times I wanted it to be a .70:1, or higher. It's why I really want a 7 speed with a .85:1 6th and .70:1 7th.

With my current 245/70R19.5 the .73:1 is great empty at 70-75, but it would be nice if it was a little lower with a camper hooked up. 5th with these tires is improved for pulling big grades.

Mine as you see in the chart is around 68 at 2000 rpm. Its perfect pulling the trailer since at 70 its at 2050 so I never have to downshift no matter the hill. Bad thing is that means I run very excessive rpm when unloaded. The Dana 80 has the option for 3.31 gears, nothing lower but that would make it much better unloaded.

Yeah I like 2000 for hill pulling, only the steepest of grades on high(5-6K+) and hot (75+) days require a downshift if I am towing the TT, which puts me at about 18K GCW and towing a big barn door.

I really do enjoy pulling with the six speed. I towed a couple of times with a buddies 97 cummins and NV4500. It felt like I was always shifting because of that gap between 4-5. Couldnt find the sweet spot at some speeds. I have to agree with AH64ID about the 7th gear. I really like the six speed for towing but I wish I could have an extra OD for just cruising empty. Maybe a gear vendors someday....

The lower rears don't always result in improved mileage.  Even with the lower rpm's, there are other factors involved………….gear leverage, electronic timing at certain rpms, etc.  IIRC, AH64ID, I believe, said the 3rd gens "stock" retard the timing around 1800-2000rpm.

Timing starts to fall off at 2,001 rpms, and is really low by 2,200 in the cruise region.

I really do enjoy pulling with the six speed. I towed a couple of times with a buddies 97 cummins and NV4500. It felt like I was always shifting because of that gap between 4-5. Couldnt find the sweet spot at some speeds. I have to agree with AH64ID about the 7th gear. I really like the six speed for towing but I wish I could have an extra OD for just cruising empty. Maybe a gear vendors someday....

That's weird since the 4th to 5th shift is the same mph and stuff as the 5th to 6th shift yet even smaller gap, so you shoulda experienced the opposite. The od on the 5600 is also numerically lower which would make it even worse.

Maybe it was the difference of rear ends??? Mine is a 3.55 and my buddies was the 4.10 gearing. That alone would not make my example very good because the trucks were not consistent that way.

 

I cant really explain it but I just very much enjoy towing with the NV5600 over the NV4500. Feels like I have more control over acceleration and deceleration.

 

Maybe I am just crazy too

 

Who knows!!??

Edited January 14, 201411 yr by Ilikeoldfords

I  just  realized,  my  Toyota pickup   5 speed  has   dang near a perfect   gap  all they way through the gears..        ring ding ding  all they  way  up to  5th.          I  have  just over 2000 miles  on it  since  I bought it  last month....  

 

   I now  know  why the  clutch pedal pad is  missing!  ha...   worn off!        I truly believe the   starter motor  has more torque  than the actual engine!   but,  it's perfect for  what I need it for!

I  just  realized,  my  Toyota pickup   5 speed  has   dang near a perfect   gap  all they way through the gears..        ring ding ding  all they  way  up to  5th.          I  have  just over 2000 miles  on it  since  I bought it  last month....  

 

   I now  know  why the  clutch pedal pad is  missing!  ha...   worn off!        I truly believe the   starter motor  has more torque  than the actual engine!   but,  it's perfect for  what I need it for!

My first ever new vehicle was a 1987 Toyota pickup.  Regular cab, 5 speed, 2WD and no air conditioning!!  Come hell or high water, that little truck with the 22R four-banger always got me 30-32mpg on the highway.  Sold it with 180,000 miles on it to an amigo that did part time landscaping.  Never saw it after that.  Just prior to selling the Toyota, is when I bought my '99 Dodge Ram 2500 with the Cummins.