I have a 2004 f150 4X4 5.4, auto with 142,000 miles on it. All maint done on time to spec. No heavy towing or hauling. Volant CAI, duel exhaust, no chip.

I get a bad shutter at hwy speed on the accelerator when in 4th gear, no gear slipage in any gears. Goes away when kicks down to 3rd. Any Ideas?

Also what are your thoughts on running 5w30 dino for extra protection with high miles. Engine and trans do not leak one bit of oil.

 

I would see if it has any codes for the transmission. Could be a solenoid or something. Kind of sounds like something affecting torque converter lock-up. Others with more expertise in tranmission matters can chime in and maybe give some more insight on the problem. If the oil pressure is still good in the engine, I'd probably stay with what got you 142,000 miles. It's just my opinion, though.

Greg B

 

If the engine runs fine and burns no oil, stick with 5w-20 semi synthetic, and I also concur with the possibility of your torque converter causing trans. shudder. I'd have it looked at.