Engine/Transmission (1998.5 - 2002) 5 or 6 speed???

[RyanB]

Hey All-



I am in the works of doing a cummins conversion into a 1989 GMC 1-ton Dually. I am building this truck for everyday driving/truck pulling/drag racing. I am putting a 12valve into it and a manual transmission. My question is which trany to go with? I was really wanting the NV5600 because of added strength seeing I am looking at putting around 500-600HP to the ground but I am also thinking about for drag racing and pulling... . do I need that extra in between gear or will it be a pain? I can bet both trany's from my supplier and there is a $1000CDN difference. For the extra $1000 I figure it will be worth getting the 6-speed just for the added insurance of strength.



What do you all think???

 

[dresslered]

I would say go for the 6-speed for the best driver/worker/RV. Or, go with the 5-speed for pullin'. Or, go with the automatic for drag racing. Sorry I wasn't much help, but each has its special application.

 

[Cowboy Medic]

I've driven both. They are both good transmissions. The clutch you put in it will be a factor long before the tansmission itself. Realistically either should hold up just fine. Make sure if you go five speed that it has the fully splined main shaft. Everyone has preferences on why one might be better than the other. Realistically if it is me I would go with the five speed and put the difference into a better clutch. The extra gear in the six speed is nice if you are pulling heavy. Running around town or whatever, I don't think it makes a difference cause you are not getting up to the highest gears. Drag racing, yes an auto would be better but very spendy as well. Six speed is an extra gear to row through and that costs time.



Overall I say five speed and the difference into making sure you got a good clutch, maybe even a dual disc. I think you will find it to be the best compromise to all of your goals.

 

[NVR FNSH]

5spd unless you find a really smooth/easy shifting 6spd. With the power you're planning you won't notice the gaps between 2/3 & 3/4 on the 5spd.



Brian

 

[Hohn]

I feel the opposite. My 6-speed shift great, and you WILL notice the gaps between gears-- some of them are substantial. With the 6-speed, you won't have to wind it out to shift, and it seems like you always have the gear you need.



Go with the 6-speed, and if you don't like the shifting, put in some MTL.



jlh

 

[BBarry]

Go for the 6spd. Mine has 70,000 on it with the factory fill and shifts better than the 5spd I had. I think I can row through the 6spd as fast most other trannys. I agree that you will notice the gap in the gears with the 5spd altough I think the 6spd could use about 3 more gears.

 

[NVR FNSH]

My 6spd shifts only marginally better that the T-18 4spd in my CJ-7. My 5spd shifted much better. And the NV5600 was replaced under warranty and has MTL in it.....



If he's really going to get 500 HP to the ground the gaps in the 5spd won't be his problem. I agree that the 6spd is great for towing but the 5spd works pretty darn good.



Brian

 

[DDT]

I had a 5 speed and it took a dump. I called NV gear and was told the nv5400 will not last pulling heavy in 5th. Now the nv5600 you can pull in any gear as heavy as you want. This is what I was told. Since I pull heavy I put in a new 5600 and like it better than the 5 speed for pulling. I think for raceing the 5 speed would be faster, one less gear to shift, But I don't see why you can't skip every other gear. I am not a racer so don't take my thoughts for fact, just a guess.

 

[Wiredawg]

Go 6spd....

Go 6 spd: you can haul heavy and if you put SBC clutch in it; you can launch in 3d gear to beat the 5spds.



Wiredawf