[mikeyman]

it only changes the angle of the driveshaft. i've had a 5" block out back and had ZERO problems. you could always get it lengthened if you are really worried about it. it doesnt wear down your transmission any more than normal, UNLESS you are trying to turn bigger than maybe a 33" tire with stock gearing. I would suggest getting a trans temp gauge first, (aftermarket or get a denali/caddy cluster) I have one and I can tell when the trans is getting hot.
when wheelin, your trans will start to get hot if you are spinning your tires ALOT and going nowhere (mudding). the important thing is to get some speed everynow and then to run some air through your trans cooler (if equipped) or even shut off the truck for a few minutes and let her cool down. With a gauge on it, you'll be able to tell when your getting hot and shouldnt need an aux. cooler. if you have one stock. it may help some but not if you aren't moving. i used to get sh!t from the parents back in the day about offroading and how it burns up the transmission. that was because they heard stories from people going mudding and blew their tranny because they got stuck and just kept spinning the tires trying to get out and the trans overheated to the point of catastrophic failure. those are the dumbasses of the world. but if you know what your doing and how to do it, you should be ok.
make sense?