well i had shuddering at each shift in my truck, the truck would stuggle up hills, there was a wierd vibration all the time, now i remove the rear driveshaft and drive it in 4 wheel, and the truck has no shudder at each shift and rides like a dream, with no vibration and pulls up hills great. is my rear end on it's way out?

 

maybe pull that dang ol' diff cover and see if you got some silvery oil, broken gear teeth, or other FOD.

 

Thats what the old mans was doin
pulled the cover and it had about an 1/8" of side to side play, it was missin three pinion teeth and the tone ring was fubar. The truck now has a D80

IMO the 70 is a weak rear

 

is there anything wrong with the rear drive line, IE. u joint, center support bearing. You dont have to remove the cover to see those.
Justin

 

That's what i would be looking at real close before i pulled the diff cover.

U-joints can cause the simpton you describe.

 

i bought u joints for it yesterday, there was the tinyest bit of play, but they werent bad, the carrier bearing is good also. im pritty concerned on the rear end.

 

If it does turn out o be the rear (sounds like it is to me) you might want to look into a Dana 80 swap. Much stronger than the Dana 70.

 

Any perceptible play = bad u-joint.

 

distorted rubber in the u joints, and if you can see where the cap has been turning in the yoke, its a bad u joint, rust is another factor, i had 2 broken needle bearings in my u joint and it felt like i had new tires w/o balancing

 

When my rearend went out it had a slight shudder to it but a constant light vibration. I pulled the inspection cover but didn't see anything but I didn't turn it. A day or two later I was crossing a bridge with concrete walls on it and I heard a roar that I haven't heard prior to that, the concrete walls created an echo chamber affect. After I got off the bridge the roar went away, turned around and rolled the windows down and repeated the process loud roar. Went home jacked her up and pulled the inspection cover, nothing till I rolled the carrier, two teeth on the ring gear and one full tooth and two big chips on the pinion. Good luck on it!