Hydra-Matic 4L80-E & ZF 4HP 24E
Park vehicle on level ground. Apply parking brake, and run engine at 750 RPM for several minutes. Shift gear selector through all ranges and return to Park.
With engine idling, withdraw and wipe dipstick. Replace dipstick in filler tube, withdraw again and check fluid level. Fluid level should be between MAX and MIN marks on dipstick. Add fluid if necessary. DO NOT overfill.
NOTE:Transmission fluid temperature MUST NOT exceed 122 °F (50 °C) when checking fluid level on ZF 5HP 24 transmission.

ZF 5HP 24
Park vehicle on level ground. Apply parking brake. Wait at least 2 minutes. Ensure transmission fluid temperature is less than 86 (30 °C). Start engine and verify idle speed is 600-750 RPM. If idle speed is incorrect, repair as necessary.
Shift gear selector from Park to Drive and wait 3 seconds. Shift gear selector from Drive to Reverse and wait 3 seconds. Shift gear selector from Reverse to Park and wait 3 seconds.
With engine idling, remove filler plug on right rear of transmission. Fluid level should be level with bottom of filler plug hole. Top off as necessary using Essco ATF LT 71141. DO NOT overfill.
Install filler plug and ensure transmission fluid temperature did not exceed 122 °F (50 °C). If transmission fluid temperature exceeded 122 °F (50 °C), let cool and repeat this procedure.

Answered by Dave H (expert)
13,682 answers provided