Thanks to all for the heads up about lisas tahoe .pdf. Very informative.

If you move the tranny forward ANY distance the driveshaft yoke will be pulled that much off of the transmission tailshaft. There is no and ifs or butts about that! Now whether or not a 1" or ? will make a difference is the question. I do know as your rear suspension goes from neutral to toward fully compressed and decompressed (your air born) your driveshaft yoke will pull even further away from the tranny tailshaft. The yoke is made to slide back and forth during rear suspension events but if it gets to far out and becomes disconnected from the tailshaft then you just chucked a driveshaft and could easily frag the backend of your transmission...or transfer case if 4x4. I have seen this happen many times but is typically caused by failed ujoints. Aint that a good day....waste your transmisson/transfer case over some $20 ujoints that people are too lazy to grease or replace when they are showing signs of failure.