I have no idea why but it seems that I may be blessed with a rear diffthat is going south. It's making some pretty hard clunks and jerks at times and is the cause of the slight vaibration I have been feeling and now I can hear a slight noise. I could be jumping the gun here, it might only be the u-joints but I kinda doubt it. I am going to have those replaced this Friday but if that doesn't it solve it, it will be rebuild time. My question to all of you is if I should go all out and do a gear swap to 4.10's if my current R&P is bad. I mean I would love to have the performance but I still need to keep it streetable on the 265 tires I have on there now. I would like/plan to go to a lift and bigger tire (maybe a 305/315) in the future. I guess it boils down to if 265's and a 4.10 would still be highway driveable. From all the calculators I have used on the net I would only be seeing about 2300-2400 RPM in OD at 65MPH, does this seem about right?

 

2400 at 70mph with 4.56 and 265/75 or equivlent in the 17inch rim size. Will need chip programmed for it 99+ or -99 use ssgear

4.2 automatic70

 

I jacked the back up and put it on jackstands and turned it by hand and engine. All seemed pretty smooth, I stuck a fence post (for leverage) under each tire and there is a little play in the bearings but not much. The rear diff does make some nosie pretty not terribly bad. There is one thing that makes me wonder. When up on the stands and the tranny in Park you can rotate the rear wheels by hand with a little force. Should this happen? I would think it should be solid and unable to turn or it couldn't hold itself on hill and it does hold itself. Could the rear LS be shot or does it just need some torque against it (ie: tires on ground) to hold itself? At this point I am sort of lost and all I can do is drive it and hope nothing breaks leaving me on the roadside. I do still plan to swap out u-joints which do not seem bad in the truck but sometimes you have to take the driveshaft out to really tell if they are bad. As before it really only is bad and vibrates when you are above at least 50 and I have found the clunk only occurs around 40mph and when RPMS drop down to around 1000. Could this be a tranny problem and not a rear diff problem? Anyways, thanks for any help you can offer but I would say the only thing I can do is to get out there and do some work on her.