Let's talk Cummins - Standard Transmission

[Howsitgoineh]

Good day all!
Hoping to get a bit of insight here from some knowledgeable folks on the great 5.9 Cummins.

I've got a 3rd Gen Dually. It's an 03 with a 5.9 came stock with the auto transmission. 47re or 48 .. not too sure.

I am currently building this truck, and would like to put a standard tranny in it. Based on my knowledge there are a few options;
2 5 speeds NV4500 and G45(?)
And 6 speed G56 and NV5600

I would like to get the NV5600 but would settle for others

I'd like thoughts and inputs on what setups you all run/like/dislike any helpful tips also appreciated.


Next thing is - I have seen some 5.7 Hemis paired with these transmissions - are they the same?? If not, would someone kindly enlighten me on the differences?

I am not a certified mechanic, I just like cars and trucks a lot, and always like to learn.

Thanks in advance all!

- P.B.

 

[sean donato]

None of the gas transmissions are compatible with the cummins, besides the v10 from what I've been told. The gear ratios are all geared for a gas engine and don't suite a diesel very well. Besides that, the diesel options are pretty easy to find.
the getrag g360 was used behind first gen 12v. They aren't set up for modern drive trains in dodges, and we're the weakest of the trans offered behind a cummins.
The nv4500 is an ok trans, and will hold reasonable power reliably. Parts are getting harder and harder to find for it. Whenever the one in my current truck dies it's unlikely to be replaced with another nv4500. Needs gl4 trans fluid, or you'll eat the synchros out of it. Doesnt really hold enough fluid to keep it from getting extreamly hot, small factory input shaft likes to break. 5th gear nut backs off. (There are fixes, but good luck sourcing one of the better shafts now adays) I also don't like the gear spread vs either 6 speed, especially if we're talking towing heavy loads, up hills. 3rd to 4th and 4th to 5th should all be a bit closer to keep from having to rev the engine so hard before up shifting to the next gear. I nearly never reccomend an nv4500 if someone is swapping anymore. I've broken a lot of them, and the one in my 79 f-350 swap has been apart many times, with lots of money dumped into custom gears and shafts trying to make it hold up. Stay under 350hp, and it will have some semblance of a normal life with regular fluid changes. Also, get the later model one with the bolt on shift tower, then you dont have to worry about the shifter poping out while you're driving. Or better yet, just avoid it.
The nv5600 is a nice improvement over the 4500. Higher factory torque input, handles modest power levels well, and the extra gear is a marked improvement for shift points. Expensive to fix, but you can still get parts for it. We'll mostly, usually just swing in a reman, or drop it off to get rebuilt when they are shot.
The getrag G56 replaced it. I'm not in love with the alloy case, or integral bell housing. I've put well over 400k miles on an 07 3500 service truck with a g56 in it, least the truck ever weighed was 9800lbs (give or take.) Regularly was heavier then that, and I towed often with it. Once it got some higher mileage on it, it was pretty sloppy shifting, eventually turning notchy/ hard to get in/out of gear. From what the trans shop said, it was typical for a heavily loaded truck to experience that issue. They can have issues with the bearing race pockets too. I've never been inside one, just easier to let a trans shop with the right tools work on it.
In short, forget the 5 speed transmissions. If you absolutely need a stick shift, get the 5600 or g56. Or if you want a trans that will hold up, just build your automatic. Once properly built they take a lot of power/abuse and keep on ticking. It's been a conundrum of mine since I decided it was time to rebuild another one of my old words and cummins swap it. Grab a 6 speed, or just build an automatic. Either way, you'll have about the same money into the swap vs building your auto.