Drivetrain problems, need help

[Zee]

Hey Calgary Jeep Association, I need to pick your brains a bit.
 
I have an unlimited rubi w/ 4.5" lift, 1" body lift and nth tummy tuck. I am noticing some vibes now, especially upon acceloration between 40-80km/hr? Nothing major but enough to have me concerned.  
 
I checked the front dive shaft, there is some play in it but I can't determine weather it is from the output yoke of the T-CASE or the slip joint on the shaft. (I grabed the shaft and pushed up and down and there was some play)   Has anyone else expierenced this? What could be wrong?  
 
Where should I go to have a quality built shaft made?  
 
The rear shaft seems fine but I would like to get a proper Double Cardan style, where can i have one made up locally? Do I have to remove the dampner?  The pinion angle has been adjusted but I guess not to it's optimal angle.
 
Another strange one, when I am comming to a stop and push the clutch in and basically coast in roughly 1 to 5 km/hr there us a rattling noise from the rear? Kinda' like when I expierenced a bad driveshaft problem.  I know this explanatoin is pretty vague but I think there is something wrong with the rear diff. The locker works fine but I think it may have something to do with the limited slip
 
Question:  When a rubi has one tire on ice andanother on dry pavement, shouldn't the limited slip engage and prevent the tire from slipping and accelorate normally?  I noticed last night when I was leaving work my right rear tire was spinning like crazy, same as my old Dana 35 inmy old jeep. Not to sound stupid but can someone explain how this device should work in this type pf situation before I take itto the dealer.  I have changed the fluid and added the proper friction modifier additive from the factory.  Could there be something wrong?  
 
Thank for all of the help,
 
Zee

[yjpaul]

I dont understand how your front driveshaft would have anything to do with anything, if your not in 4 wheel drive going 40-80 km/h.  It should have nothing to do with your forward velocity.

[Zee]

yjpaul,

The front driveshaft still rotates, I do not have hubs on the front diff to disconnect the front driveline.

 I am thinking that my double cardan joint on the front shaft has some problems. What I am asking with respect to the front shaft is can there be some play?  Mine feels pretty loose at the slip joint and at the T-Case output?  The u-jounts look and feel like they are ok.

Is "play" normal on the front driveshaft?

[Bnine]

DSI (Drive system inc) is the best place in town to get a CV built.

They can redrill you dampner and install a cv on it.

Honestly I'd get that done first. You are pushing close to 7 inches of lift over stock from pinion to t-case output. Thats a lot even for an unlimited.

DSI can look at the front shaft while you have it in there. The center section is likely worn. Common problem. They will rebuild the front shaft for you for 150-200.

hth