Hi oil fans! Mom handed down her pickup to me. 2002 Silverado 1500 4wd, 40k miles. Do I need to change the ATF and/or Diff fluids? This truck was kept in a heated garage for the first 8 years and the next 4 in an unheated but well-protected garage. Should I think about changing either of the ATF/Diff fluids or is it still fine? Any advice (provided it's not "now give the truck to me!") would be very welcome. TIA.