Retro51, you should get the trans from the donor too, as they are both controlled by the PCM. Simply taking the trans out of the equation will require some reprogramming and the need for a VSS (Vehicle Speed Sensor) box of some sort. The OBD-2 computers watch all kinds of stuff. Yours may want to see feedback from anti-lock sensors too. Just want you to have a handle on what to expect.
Doctasuds, the viscous BorgWarner AWD unit in the Astro resists even small differences in front/rear driveshaft speeds in a big way. Many folks with that unit run 8-10PSI more air in the front tires to get the diameters more precisely matched. This reduces rolling resistance. Could get you 2-4 MPG hiway. The best way to do it is to do roll-down tests on a flat smooth road somewhere and see wich combo rolls the farthest. Mikey
