I have a 2000 Ford F-150, 5.4L, 2-wheel drive truck with an automatic transmission. Very soon after the truck warms up, I get a 1 to 2 second flute/squeak sound when the truck upshifts in all gears except first to second gear. It always happens when driving up hill or accelerating on level ground. I’ve talked to local mechanics and they’ve never heard of this in an auto transmission. They suggested I look for vacuum leaks. Found none. Totally perplexed. Anyone out there who can advise me? Mahalo!
Have you checked the fluid level? If you have not done so I would have the transmission pan removed, the fluid drained and replace the transmission filter. Fill it with the proper tranny fluid and see if the sound goes away. I have heard torque converters make a similar sound when the transmission fluid was low.
Sorry, I forgot to mention that the trans fluid level and color is normal. I have 100,000 miles on the truck. Last trans fluid change was at 30,000 miles due to other work being done on the truck at that time. Could it be he trans filter causing the problem? Thanks again.