Tranny & T-case Info

[cbrandt]

Here it go's. I have been thinking about this project for about 10 years (ever since I fell in love with a 79 GW...) I want to build a Cummins powered GW. I have purchased a Cummins 4Bt (the 4 cylinder version of the 6BT that Dodge uses) a TH475, NP205, and a narrowed Dana 70. All I need now is the FSJ..
I am now rethinking the tranny and T-case selection. I think this project needs an overdrive, a 700R4 comes to mind. The engine adaptation is easy, but my T-case selection becomes a bit tougher. The 205 I have now is divorced so I can put it behind anything. But I like the thought of the NP241 that Chevy uses behind the 700R4. This is an integral mount with the tranny and has a pretty good low range. I would like to know if anybody has done a 700R4 swap into a FSJ ?

Also looking fo a ratty donor to work out the details of the swap on before I cut into the beautifl 91 that have waiting to purchase...

[bigjeepguy]

I would say use a stickshift, to get a good stout overdrive,(you want overdrive)a 6BT is governed at about 2600 rpms, and in my truck top speed in direct drive, running it to the max is 65, and it should not be run like that for long stretches, automatics and Cummins diesels do not mix my dad works at cummins, and knows someone who swapped in a 3.9 and bolted it to a TH-400, the tranny was gone in under 50,000 miles, and on his company truck with a heavily modified 5.9 that pulled 4000 rpm ate a C-6, built to be used behind engines over 600HP in 40,000! however his new company truck, a97 dodge with a 5 speed has eaten 4 trannys, but it weighs about eight tons. the 205 and the dana 70 are good coices, probably overkill with a 3.9 though, but for an auto with overdrive, a 4L-80E would probably be the best, jet builds them for 700 lbs/ft, which a 3.9 will probably not be packing.

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Jonathan landon
1973 J-4000 3602v ,TH-400
Dana20,Dana 44's