What are the signs of a dirty transmission filter. When is it time for a transmission filter change?
Shouldn’t be any signs, most transmission filters are changed by age instead of fluid color.
It is recommended that the transmission filter and fluid be changed every 12,000 miles according to the manufacturer. for 3/4 ton trucks and larger. Every 15,000 miles for 1/2 ton trucks.
Use Dexron lll(r) or its superseding fluid type.
Check the level of the fluid at least once a month. The fluid level should be checked with the engine at normal operating temperature and running. If the truck has been running at high speed for a long period, in city traffic on a hot day, or pulling a trailer, let it cool down for about thirty minutes before checking the level.
- Park the truck on a level surface with the engine idling. Shift the transmission into P and set the parking brake.
- Remove the dipstick (on newer models, you may have to flip up the handle first), wipe it clean and reinsert if firmly. Be sure that it has been pushed all the way in.
- Remove the dipstick and check the fluid level while holding it horizontally. All models have a HOT and a COLD side to the dipstick.
Transmission Filter Change and Fluid 1988 GMC 1500
- The fluid should be drained with the transmission warm. It is easier to change the fluid if the truck is raised somewhat from the ground, but this is not always easy without a lift. The transmission must be level for it to drain properly.
- Place a shallow pan underneath to catch the transmission fluid (about 5 pints). Loosen all the pan bolts, then pull one corner down to drain most of the fluid. If it sticks, VERY CAREFULLY pry the pan loose. You can buy aftermarket drain plug kits that makes this operation a bit less messy, once installed.NOTE: If the fluid removed smells burnt, serious transmission troubles, probably due to overheating, should be suspected.
- Remove the pan bolts and empty out the pan. On some models, there may not be much room to get at the screws at the front of the pan.
- Clean the pan with solvent and allow it to air dry. If you use a rag to wipe it out, you risk leaving bits of lint and threads in the transmission.
- Remove the filter or strainer retaining bolts. On the Turbo Hydra-Matic 400, there are two screws securing the filter or screen to the valve body. A reusable strainer may be found on some models. The strainer may be cleaned in solvent and air dried thoroughly. The filter and gasket must be replaced.