- 1). Raise the Suburban with the jack, place jack stands under the frame and lower the vehicle onto the stands. Use a flashlight to inspect the transmission for leaks. If the transmission has been leaking for a while fluid and dirt will have accumulated over the transmission. It will need to be cleaned to pinpoint the leak.
- 2). Look closely around the service pan. Pan gaskets are the most common leak. These are easy to service and usually a new transmission filter is necessary. Replace the gasket and filter if the gasket is leaking.
- 3). Move to the forward area of the transmission where it is bolted to the engine. If fluid is seeping from here, the front seal has failed, and the transmission must be removed for repair. This usually indicates the pump bushing has dislocated, allowing fluid to leak past the front seal. In this case, the transmission must be removed. Consult a qualified shop for this major repair.
- 4). Shine a flashlight around all of the electrical connectors on the transmission. All of them have seals that must be inspected. If any connector is leaking the repair is internal. Access is gained through the pan and the transmission does not need to be removed.
- 5). Move to the back of the transmission for the final undercarriage inspection. Examine the tail shaft seal where the drive shaft spline fits into the transmission. If this seal has failed the tail shaft bushing should be replaced with the seal. The transmission does not need to be removed for this repair.
- 6). Lower the Suburban, raise the hood and inspect the transmission fluid. If it is milky the transmission cooler is leaking and the transmission will have to be removed for service. The cooler will also have to be replaced. The cooler is located in the radiator. At times the cooler will leak into the radiator and transmission fluid will be in the radiator.
- 7). Remove the radiator cap when the engine is cool. Inspect the fluid for oily, reddish-brown residue floating on top of the coolant. This indicates the transmission cooler is leaking and should be replaced.
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