My 2001 F150 Lariat Supercrew now has 160,000 miles. Most of those light duty, but recently did some heavy trailering. After hauling several loads of stone, the transmission would slip a little and slightly clunk upon normal acceleration. Took it to my Ford dealer and asked for a fluid flush AND filter change. They called me after the flush was done and realized they forgot to change the filter - said they normally don't do both - (don't believe it). Truck ran fine for a month, now same symptoms again. Been told by some people to drain the trans and replace filter, might be some trash caught up there from flush. It does this about 15% of the time, but is slowly getting worse. Last fluid/filter change was at 125k. Can anyone help?

 

Believe it - they don't drop the pan, they just hook up the machine and replace the fluid.

 

If there is enough junk in the filter to make a difference the trans is already toast.