2001 1500 5.9 4x4 235xxx. I was driving a 4 hr trip on cruise control at 75 mph. Then she decided she had no gears. Stopped immediately checked fluid which was alittle low. Added some. When i turned the truck of an it sat I'd get all my gears back for bout a min then nothing. So i changed the filter an strained the fluid which was pretty brown almost black but not burnt. There was barely any metal shavings in the fluid or pan. The biggest sliver was bout the size of this letter (I) I drove home the four hours no problems at all. Got up the next day to drive it an it all started all over again. My question is can i completely drain an put brand new fluid in. Ive heard all my life that you cant do that and if you do you will mess up the trans. Please help.

 

Actually, yes, you can, and eventually you will have fairly nice, clean, fluid in there. Doubt it will solve your problem though....... Probably have a sensor failing, would hurt to change the governor pressure sensor, and solenoid, next time you are in there.

Also, there IS a danger that the contaminants in the fluid are what is keeping the trans working........ Given that you have 235K miles on it, you have already done REALLY well. It is probably time to start saving for the rebuild.