Transmission/ T- case question

[Jtaylor28752]

I have a 2002 Yukon 4wd 5.3 i had some issue slipping out of overdrive and not wanting to engage reverse. Drive it that way for months until i could have it rebuilt. Last week it started making a grinding/ whining sound when it changed gears so i parked it had it towed home and messed with it a little bit. When putting it in reverse it would start the whining/ grinding sound without acting like it was engaged but the speedometer was bouncing up and down up to about 15. So after i got all 4 wheels off the ground when in neutral i turn the rear drive shaft and it turns freely but the front one turns also (keeping in mind it's in 2wd mode) the front wheels wouldn't turn just the front driveshaft was under the impression the t- case shouldn't be locked with the front shaft while I'm 2wd? I don't know I'm going to go ahead and rebuild the transmission since I've known for awhile it needs it, should i go ahead and do the t-case as well or what? The speedometer bouncing is what threw me off since the vss are on the t case
Thanks in advance
Justin