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Thoughts on the Drivetrain associated with the 6bt Cummins diesel trucks

SpeedlabDan

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OK so I'm leaning towards a 6bt swap but the Drivetrain is up for debate. My first choice would be an Ally 1000 but the associated engine adapters then tcase adapters are pricey not to mention tcm.

So, what about the driveline behind the engine in a 4wd? Is it a 727 or version of? What tcase? Right side drop? Is it strong enough for a tow rig? After all this is a 3/4 or one ton donor vehicle.

In the interest of cost, I think this could be a good option. Just tossing around the idea, let me know what you guys think or if you have used this combo in a Gm.
 

1977k5

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The trans depends on the year.

89-93 have right hand drop NP205's, 94-02 are driver's drop NP241's.
 

Kay86K5

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According to my understanding, there are adapters out there...but most of the dodge tranny's were 29 spline output. But ORD sells a 29 spline input conversion for 205's.

I would rather find a 6bt with a dodge NV4500 behind it, and then just work on adapting your GM205 to that...sounds like the easier way to go

Others that have done the swap (or are doing the swap currently) will probably post up. I decided to go 8.1/GM NV4500/GM 205 in my crew cab instead of the Cummins route, so I don't have much experience with the details of the Cummins swap
 

SpeedlabDan

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According to my understanding, there are adapters out there...but most of the dodge tranny's were 29 spline output. But ORD sells a 29 spline input conversion for 205's.

I would rather find a 6bt with a dodge NV4500 behind it, and then just work on adapting your GM205 to that...sounds like the easier way to go

Others that have done the swap (or are doing the swap currently) will probably post up. I decided to go 8.1/GM NV4500/GM 205 in my crew cab instead of the Cummins route, so I don't have much experience with the details of the Cummins swap
I was on board with the 8.1 swap but I'm hoping for better fuel eco towing with the diesel and my truck was originally a 6.2 so it has diesel roots haha.
I also want to stay automatic with some sort of overdrive so the nv4500 is out
 

Bent77

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Is the 904 the automatic that came behind these? The 205 mates to those. The 205 I am using cam from a 6bt/auto.

The spline input was different as mentioned above
 

nvrenuf

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The 727 was the trans used with the 6bt / 205. My understanding is the 904 is the smaller Dodge auto trans.
 

Bent77

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The 727 was the trans used with the 6bt / 205. My understanding is the 904 is the smaller Dodge auto trans.
So I did more Google fu and got factory 618?


So I vote Allison or 4500
 

obijuank5

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Dodge automatics are 23 spline up until 2007.5 and the dodge 205 with 23 splined is relatively easy to adapt to each other. 23 spline is kinda weak though for how much power it might need to put down.
 

Kay86K5

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I was on board with the 8.1 swap but I'm hoping for better fuel eco towing with the diesel and my truck was originally a 6.2 so it has diesel roots haha.
I also want to stay automatic with some sort of overdrive so the nv4500 is out

Understandable. For what it's worth, towing mpg with a Cummins will be relatively the same as towing 8.1 mpg. Where diesel beats the 8.1 in mpg is empty driving. My 99 cummins gets about 17-18 empty, but towing with that turbo spinning a lot, it's closer to 11-12. Sure the 8.1 will only get 10-12 empty, but even with a 10k load behind it, it'll still get 10, haha. Just more FYI is all.

I'm all for cummins swaps...I heavily considered it with my crew cab, but with my uses for the truck and everything else considered, the 8.1 fits my bill better
 

b454rat

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My understanding is if you want an Allison behind a Cummins, there is no way for the trans ECM to talk to the motor. I've read than you need torque management even on the Allison, the Cummins just makes to much torque down low....
 

SpeedlabDan

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Understandable. For what it's worth, towing mpg with a Cummins will be relatively the same as towing 8.1 mpg. Where diesel beats the 8.1 in mpg is empty driving. My 99 cummins gets about 17-18 empty, but towing with that turbo spinning a lot, it's closer to 11-12. Sure the 8.1 will only get 10-12 empty, but even with a 10k load behind it, it'll still get 10, haha. Just more FYI is all.

I'm all for cummins swaps...I heavily considered it with my crew cab, but with my uses for the truck and everything else considered, the 8.1 fits my bill better
Yeah I have heard that about the 8.1 that way its just gonna be more work I think for swap
 

SpeedlabDan

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My understanding is if you want an Allison behind a Cummins, there is no way for the trans ECM to talk to the motor. I've read than you need torque management even on the Allison, the Cummins just makes to much torque down low....
That's why I mentioned the tcm. It's a stand alone controller for the torque management etc. Destroked makes one and a few others but the adapters on both ends are really spendy
 

Kay86K5

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Yeah I have heard that about the 8.1 that way its just gonna be more work I think for swap

Not necessarily...the 8.1 swap is literally a bolt in affair into a square body. Cummins swap actually requires a bit more fab work. Both are bitchin swaps though
 

SpeedlabDan

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Not necessarily...the 8.1 swap is literally a bolt in affair into a square body. Cummins swap actually requires a bit more fab work. Both are bitchin swaps though
Good thing I'm a fabricator over a mechanic haha honestly the biggest reason I'm Goin back to diesel is bc it has big fuel fill necks :haha:
 

SpeedlabDan

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So I did more Google fu and got factory 618?


So I vote Allison or 4500
I like the Ally the best but it's a really expensive venture. The trans is also gonna cost over 1500 used I'm just hoping a dodge 1ton Drivetrain is worth picking up just to be lazy even if I'm fabbing up mounts and cross members. Unless of course I come across an 8.1/ally/tcase in a wrecked truck or something
 

SpeedlabDan

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Dodge automatics are 23 spline up until 2007.5 and the dodge 205 with 23 splined is relatively easy to adapt to each other. 23 spline is kinda weak though for how much power it might need to put down.
Aren't the 23 spline units in dodge 1tons?
 

sweetk30

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med duty trucks could be had with cummins and Allison trans all as 1 unit .

we have a 2007 f650 at work with that combo
 
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