automatic tranny overfill

[Steve M]

I took my truck in last week to have a rim replaced under warranty. While I was there I told the mechanic about the oil level in the rear end being a little low. He apologized and re assured me that 1" below the fill hole is not a problem and topping it off with Valvoline full synthetic GL5-MT1 75w-90 is also not a problem. I think he might have redone his PDI... When I got the truck back, it felt like a brake was dragging. Even at 65mph I was into the throttle to maintain speed. Mileage was down 2mpg. This morning I decided to check each wheel for a dragging brake even though they all felt about the same temp after driving around town. While nosing around under there, I noticed a few spots of oil on the hitch receiver. To shorten the story, my transmission was 1.5 quarts overfull and the fluid was full of air. I syphoned the level down to normal. Just another thing to check for low power and mpg... Symtoms are dragging, mushy or erratic shifts, harsh engagement when put in gear, and signs of fluid blown out the vent. Vibration is also a sign of air in the fluid.
The mechanic is a very nice person and owns a HO/6spd 4X4. I contribute this to a forgivable oops.