1999 Tahoe issues..this is getting old

[99 Mob Mobile]

I have a 1999 Tahoe 4x4 LT with currently 143,425 miles on it..7500 miles on a new motor.which i had to replace this spring..Wasnt thrilled but it did have around 135k..The chain "somehow" got stretched in the transfercase so my 4x4 doesnt work but its going down to have that repaird next week..

i currently have 2 other problems..if i can fix them i might hold onto this truck alittle bit longer but if i cant fix these problems its Gone..

A have a Driveline vibration that i cant quite figure out where its coming from..I've put all new U joints on.along with new monroe Shocks..it only happens right around 50-60 and its getting worse..you know that sound when someone in the back of a car rolls down a window all the way while the rest of them are shut and you hear the wind making that obnioxus thump thump thump noise?Thats Very simular to what my vibration is like..a very simular noise but not that loud..but its annoying adn its defintly noticable..I've shifted it into nutral.. downshifted into third and it still makes it so i know its coming from the driveline..I was told that it could be my tires..i have Michelin 245's LTX M\S which are very nice tires..I've driven other vechicals with bad tires..broken bands etc and thats more of a Shake than anything else..I feel nothing in the steering wheel at all..I can hear it more than anything..

Yes all of my windows are rolled up..I talked with some other poeple an dthey suggested it was a U joint..I replaced them.. its still there..poeple have ridden in my car and they ask if i have a bad U joint..Thats really what it sounds like.. a Bad U joint..but its not..The balencing weight on the driveshaft is all there..I've grabbed the output shaft adn it all seems tight..if i drive over 60 i really cant hear it..

Is it possible i have bad bearings in my Transfer case? I would like to think if i did it would cause my seals around the output shaft to leave but everthings dry..its not tight tight if i push on the head of the driveshaft by the output shaft..but it sthe same as my 2001 Yukon Xl and i have Zero vibrations or hums..

it seems like its just slowly getting worse and worse adn its driving me insane..its as tight as a rock where the driveshaft goes into the rear end..its not there..Any suggestions? anyone had a simular problem?

I'll have the garage check out all of my bearings and replace anything thats loose when they repair my transfer case so my 4x4 works..but i got afeeling that isnt going to solve my problem..if it doesnt i dont knwo where else to look..

Second issue thats really annoying me is a thumping clunking noise I get on the front end between the speeds of 15-35 and after 35 its gone..I tried moving my CV Shafts to see if they were loose and they are as tight as a rock..my front differntly fluid is full..I've shut the engine off and shifted it into nutral and its still there.. I notice that it alot louder after i drive it after its been sitting awile..I notice it most in the morning when i head off to work..Could it be my tires? they have about 10% tread left..but i would think if i had a broken band i would really notice it at higher speeds or see it..

Its all beyond me...if you need to ask me anything feel free to do so and if u can think of anything please let me know..

[777stickman]

Maybe swap wheels & tires with a buddy just for a test. That would eliminate some of the ?'s.

[99 Mob Mobile]

Good idea..I can just swap the ones on my Yukon..I just had those put on 9,000 miles ago..I'll try that tomorrow