The only disadvantage I see to your set-up is that when you go into "low" your extremley low. The advantage to having the dual cases is that you can select how low to go. I know your trying to stuff all this in a Jeep, so space is at a premium. I used to have a Chevy Blazer with the SM420, and that 1st gear is a crawler. Fortunatly 2nd gear is low enough to start out in, so you'll have some flexibilty with that.
I think you'll be very happy with your set-up, and you'll get around the disadvantages, and excell with the advantages.
Erik
I actually have atlas4 speed so my gear ratios in the t-case are
1:1, 2.72:1, 3.8:1, & 10.34:1
So I can chose between
Overall
27:1
74:1
103:1
and 278:1
I think this range would be comparabe to duals? I actually was going to do duals, but not having a t-case to start with would have made it too expensive I think? (I got a deal on my atlas) And I couldnt afford the driveshafts becoming shorter with my wheelbase, with the atlas only being 15 or so inches thick it actually lengthened the rear and front d-shafts and their almost interchangable so One spare will work front or rear...
But when I see people on here puting tripple cases in with ratios in the 1---s I was real curious what other people are running and how they like it.... I have not spent much time in the rocks but thats what I have been building my rig to handle...
The sm420 isnt doesnt have od? does it? I know it has an even lower granny than my 465
