boohoops

To begin, yes I have used search and have found too many results about shuddering but none sound quite like my situation. Everyone's seems to happen at low speeds or during turns or from a stop. Mine occurs at cruising speeds.

Recently noticed that at speed, when the truck (2004 F150 5.4 4x4) downshifts from 4th into 3rd to maintain speed (say going uphill), and back into 4th it'll do a shudder that feels almost like I'm hitting a rumble strip. At low speeds it doesn't exist so I'm not sure if it's the rear end clutch packs but I don't want to rule that out just yet. Everything seems to work just fine the rest of the time... Any ideas?

Newfiedan

Check the usual suspects like bad u joints, drive shaft out of balance etc. Fyi the u joints are staked into the driveshaft and they require a special tool like a hole saw to remove them. I had mine removed and heavy duty ones installed with grease nipples. A lot cheaper than fords answer which is replacement of the entire driveshaft.

BLUENGRAY05FX4

Have you noticed the problem when you start stepping on the gas, say around 45mph? I thought my transmission was hunting for the correct gear, but it turned out to be a missfire... I recently replaced the sparkplugs and it is gone. It definitely feels like the transmission is shuddering when it does it.

-Greg

StanF

It could be a ton of things. I had the same issue and have done quite a bit of research. Two main reasons come to mind:

Inspect/test your COPs (coil on plugs)

Try Lubeguard Dr. Transmission Shudder Fix
http://www.oreillyauto.com/site/c/de...0444&ppt=C0207
I tried it, and it actually solved my issue. Your results may be different.

Possibly also your spark plugs.

boohoops

Thanks guys, I'll definitely be checking that stuff out this weekend. Thankfully it's not my dd haha and fingers crossed it's nothing major