Rear Shocks

[Gottmud]

I put the truxxx levelling kit on my truck 2 months ago. I am very very happy with the results, but I have some observations that need some answers.

Once the levelling kit was on (35" Toyos), I levelled the front to manufacturer specs. The whole truck sat 41.25" floor to bottom of fender, all the way around. Yes, i also did the measurement from center of hub to bottom of fender to manu specs. I measured the truck at the weekend, and everything has dropped 1/2" exactly all the way around. It know seems i have a hollow sort of a creaking sound coming from the rear of the vehicle only when its cold. Once the truck warms up, it goes away. Maybe shocks ????
Once they get warm from working, they pressurize maybe, and the noise goes away ??????. It is not the truxxx kit, that I know.
Anyone else have those sort of problems yet...