5 Speed Or 6 Speed?

[JSmith]

What is the big difference in 5sp vs 6sp? Is one better than the other? Is the 5sp available with the HO CTD?

 

[FATCAT]

Go with 6-speed

From what I know, the 6 speed can handel more tourque and power than the 5 speed, and the 6 speed does not have the "5th" gear nut problem due to the main shaft not being fully splined. The 6 speed should also be smother shifting due to the additional gear.

If I had the chance, I would have goten a 6 speed, but it was not offered in 1997.

 

[kchristopher]

The extra gear is in the middle, so the gear splits are better with the 6 speed. In 2001, the 6 speed was required with the HO and not available with the other engines.



Having driven both, get the 6 speed.

 

[TomGolden]

As I recall reading somewhere, the input shaft on the NV5600 in the 2001 HO trucks is slightly thicker than the input shaft on the earlier 6 speeds available on 1999 & 2000 trucks. Also, compared to the 5 speed gear boxes, gears 1 & 2 are identical, and supposedly 6th gear is identical to 5th in the 5 speed trannys, and gears 3, 4 & 5 are a little closer together than 3 & 4 in the 5 speed trannys, so it's better for towing.



I have always loved shifting my own gears, and the more the better so that was one of three factors that made me get the 2001 HO Cummins.



Tom

 

[kchristopher]

Here are the ratios that I've cut/pasted from a popular OD manufacturer's website:





NV4500-



1st 5. 61

2nd 3. 04

3rd 1. 67

4th 1. 00

5th 0. 74



NV5600-



1st 5. 63

2nd 3. 38

3rd 2. 04

4th 1. 39

5th 1. 00

6th 0. 73



Comparing the 6 to the 5:

As you can see, 1st is practically the same. Second is slightly lower. Not much, but it you can tell it is easier for 2nd gear starts in the real world (personal experience). Notice the huge difference in the 2-3 split. Ever try to make a 2-3 shift in a 5 speed going up hill pulling a load? If you wind it out to 2500 rpm, the speed drops to just under 1400 rpm, almost a 50% drop. In a 6 speed the drop is to 1500. It's a difference you can really feel. On the 3-4 shift, the 5 speed goes from 2500 to 1500, the 6 speed from 2500 to 1700. Then you get a 39% drop to get into direct drive. O/D is practically the same.



I've rounded figures and there may be some math errors here, but you can see what I'm getting at.

 

[Dfeland]

6 speed is VERY large!

The 6 speed trans physically is WAY larger than the nv4500 maybe in the truck they look similar but get them out on the ground together and the 6spd should be in a semi! Most shops, in fact I would say all dodge dealers do not even have a press big enough to get the big boy apart. I have seen two replaced and they just exchanged them out even though it was only a syncro problem. Go with 6 definately!