I have a 02 suburban z71 I got a while ago and I've done a lot of work on it has 258k on it now I've done the power steering pump, fuel pump, knock sensors(relocated), front brakes, LF wheel bearing, alternator and serp belt it has all stock drivetrain from my knowledge with mostly highway miles on it as the first owners used it to go from arizona to Washington. I was wondering if anyone on here on here with a bit more experience and info on these trucks would let me know of anything else I need or should do to bullet proof it before I go on a road trip the transmission shifts pretty clean but from 2nd it takes a sec to shift and it doesn't feel like its slipping just taking its time if that makes sense

 

I would change tranny fluid & filter, front/rear diff & trsnsfer case fluid, and brake fluid

 

I would change tranny fluid & filter and rear differential oil; if 4WD also do front diff & transfer case fluid.

Personally I wouldn't do a brake fluid change.

 

At that mileage I wouldn't do a full fluid and filter swap on the transmission. I would just do a drain and fill. The fresh fluid has enough detergent to clear the filter a bit and it will also clean up some gunk as it absorbs it into the fluid. flushing or swapp[ing the filter at that mileage has a higher likelyhood or doing more harm than good. I would also change the fluid in both differentials and the t-case, that can only help. Brake fluid should be changed... but make sure that all of the bleeder valves will open and have an extra wheel cylinder or 2 ready for the rear brakes before you do it. Also if they haven't been done in 100k replace the shocks. You will get better gas mileage.