My truck has a mileage of 135,000 miles. It was running fine until today. I tried to go into reverse but it was unresponsive. I had to put it in neutral and push it downhill. When I put it in drive, it had difficulty driving forward and seemed very sluggish. The RPMs were very high while the truck was moving slowly. Also, there is this noise that is noticeable when the engine is running while the transmission is in park. The sounds are similar to those of turbo engines, and are only present in park. The noise seems to be comming from the area under the transmission. I checked the level of transmission fluid and it is okay. Several months ago, I had done the transmission oil flush. Do you have any idea what is wrong with the vehicle? Thank you in advance.
The oil flush may have caused the varnish build up to be loosened up and after driving a few months the clutches have washed out and are slipping. You may have to have the transmission rebuilt or replaced. I recommend having a mechanic inspect your loss of power symptoms firsthand to verify the diagnosis and recommend repairs. Once that is done, an accurate fix can then be performed.