hi there im new to this forum group, and i have a 1990 300 te 4matic and all is somewhat smooth , with her .
Ive browsed most sites and almost all of my symptoms that i have found about my car they are pretty well even across the board for my estate wagon,ha . german qaulity ,

i have found no question like the one i have posted in a few other forums and i have yet to be responded to , so here it is;

i have read in my manual that there is a "test valve" in the engine compartment , which, activates/deactivates the hydraulic funtion of the transfer case , also disabling the load level system hydraulics,
in my query i pose this , in hopes that i can prolong the transfer case 's lifespan(it seems to funtion although i have to bleed residual air in the valve body, to correrct the 4 matic lght) is any one in this forum aware of this valve and any possible damage that may ensue,from prolonged driving in this test mode?
i will have many ohter posts like this one i have a vague idea and i am looking for second opinions sorry for the size of this post