Spring is the right time to go through your GM truck top to bottom — and if you're spending a Saturday on it, do the drivetrain and the exterior in the same session. Here's how I run through it on a Silverado, Sierra, or Tahoe coming out of an Ohio winter. Transmission fluid check: With the engine warm and the truck in Park on level ground, check the ATF level and condition. On the 6L80, pull the dipstick and look at the color — it should be a clear reddish tone, not brown, not black. Smell it. Burnt ATF has a distinct sharp odor that's unmistakable once you've been around it. Dark fluid past 40,000 miles with no service means a pan drop is due. On the 8L90, which uses a fill plug instead of a dipstick on many configurations, you check fluid level at the fill port with the transmission at operating temp. Dark or burnt Dexron VI means a drain-and-fill before towing season starts.
Recommended Products
Dexron VI ATF
Search AmazonThe correct service fluid for 6L80, 8L90, 4L60E, and 4L80E applications. If your spring ATF check shows dark, degraded fluid, a drain-and-fill is the right call before towing season. Pick up at least 6 quarts for a 6L80 pan drop. Dexron VI is backward-compatible with Dexron III for older units as well.
Check Price on AmazonChemical Guys 10-Piece Car Wash Kit
$99.99Everything you need for a proper spring decontamination wash on a GM truck. Includes pH-neutral car wash soap, microfiber wash mitt, drying towels, detailing spray, and applicator pads. Well-suited to full-size truck panel sizes and the flat hood and roof sections where road salt accumulates heaviest over a Midwest winter.
Check Price on AmazonBlueDriver OBD2 Bluetooth Scanner
$89.95The spring scan is not optional if you're about to put a trailer behind this truck. BlueDriver reads GM-enhanced transmission codes and live TFT data — the two things that tell you whether your 6L80 or 8L90 is ready for a summer of towing or whether there's a developing issue that becomes an expensive roadside problem in July.
Check Price on Amazon