I have had this impact wrench for about 20 years. It never has been all that good. It had gotten so bad the 3/8" air ratchet was stronger.
Today I needed it to remove the nut from the tillers flywheel. So I pulled it apart and washed the guts in the ultrasonic cleaner. The parts did not show any discernable wear. I reassembled it using ATF. It works at least as good as it did when it was new.
The images here were taken to help in reassembly.
I also opened up the air chisel/hammer and coated the barrel with ATF. Worked better too but I doubt it will continue to do so when it we get warmer temperatures.