I cranked up the keys on my 06 chev. It leveled out nicely i think. no real difference in handleing or anything. probably got .75 " out of that.
THEN not to long after that i wanted to run a little taller tire and I bought factory Ford f150 keys (think they were about $50 for the pair) they worked in place of the factory chevy ones and yeilded 1.5" and if i cranked them all the way up prob a little more than 2" but i ran them in the middle of the adjustment. and cleared a 305/65 r17 E no problem.
When i did the f-150 keys i ended up putting air bags in the rear to eliminate the sag when i was towing. Otherwise still no significant difference in handling or ride quality. except after my inner ball joints started going.
THEN i traded it in for a 2500.
