Truck has done this 3 times now. Its only done it going up hill since thats when it downshifts and holds the lower gear for longer. But here it goes:

Driving uphill, doing 70-75 and it downshifts to 4rth Id assume and RPMs jump to 4000. After about 1-2 minutes, I get a tapping sound coming from the passenger side. As soon as I let off the gas and coast a lil bit, noise goes away. Ive parked as soon as this happens and noise is gone.

Its not pinging, not sure if Im losing power since I let off the gas as soon as I get that noise. No CEL, running motorcraft 5/20 and motorcraft filter...temps have been mid 80s and truck isnt overheating. Only does it when revved up for a while...cant duplicate it parked cuz of the rev limiter.

Could this be a dirty/sticking lifter? Any known fixes for this? I dumped some Marvel Mystery Oil in the crankcase hoping it helps. Anyone run into this before?

Thanks!

 

I recently bought a ranger with a stuck lifter issue. From what I heard, its from engine sludge (Which WAS confirmed after removing valve covers). I've been told to use an engine sludge treatment (Found at any parts stores). If this doesn't help, could be a collapsed lifter in which case it needs to be replaced. Not sure if cam needs to be replaced with lifters,

 

i have this issue also
but i been living with it because i just put this engine in and i know there no sludge in it
i dont feel like taring into it yet though
but i will need to do it at some point in this engine's life span -- but im waiting untill i can get an aftermarket cam also

info ive found on the issue

you do need to replace the lifters if any problems with them
the lifters are not rebuildable
the cam dose not have to be replaced unless damage is found

hope it helps

 

added some marvel mystery oil and problem went away