Rotate your tires front to back and see if the bouncing follows.

Buy some motor flush and 6 qts of cheap oil,a cheap filter, 5 qts of good oil and good filter.

Add motor flush and let idle according to directions.

Drain oil & remove filter, once oil stops dripping out, pour a qt of oil into engine with oil plug removed. You will be amazed how much more nasty oil comes out.

Fill filter with cheap oil and install it. Replace plug and pour in 4 qts of cheap oil.

Drive this for a day or two and repeat steps except use the good oil & filter.

FYI Use 5W-30, Purolator, Bosch or Fram tough guard filters. Look up filter for a 2000 S-10 4.3liter 4x4. It is 1" longer for more filtering capacity.