bcher

I recently had trouble with my 2008 FX4 shuddering when downshifting from overdrive. I tried reading several posts some said try a bottle of Dr. Tranny. I went to Ford and bought a 4oz bottle of Friction additive modifier for $6 problem solved for now. Though this might help someone with the same problem.
Thanks

justinkobus

Have you ever changed your plugs and coil packs? When I would drive my truck and about 45 mph and lightly step on the gas it would start to buck a little bit and shutter but once it down shifted it would go away. I changed my plugs and the problem was gone. The check engine light will not come on when this happens bc it's a low volt misfire and the computer can't read it. I thought it was my transmission but it wasn't, I hope this is helpful

zmadams

Same thing happened to me. When the torque converter would unlock in 4th it would would shake just for a half second. Trans pan drop and trans filter change solved the problem.

FANGS99

Try adding some friction modifier to the trans fluid.

Jet A-1

I'm glad I ran across this thread. I have the same shuddering issue. It happens when in overdrive, when the truck is "lugging" along at highway speed and the rpms are maybe 1500 or so. Step into the throttle just a touch and BAM, it shudders like it has a dead miss. I was thinking plugs at first (God knows when they were done last) but when you give it just enough gas to drop down a gear or disengage the O/D on the button the problem disappears and the truck accelerates as good as ever. Very strange. No doubt the plugs should be done so I guess I should do that regardless. It isn't throwing any codes either. I was going to see if the Predator programmer could raise the lockup rpm so maybe I could eliminate the shudder that way. I guess a transmission fluid and filter change wouldn't hurt either. What part number is the Ford friction modifier?

wolfy53

Jet it's your plugs. Mine did the exact same thing. New plugs fixed it. Fortunately I found this out on mine on the test drive. 98k miles the plugs were way way worn out and about 5 times the gap as specified.

I'm not a fan of adding friction modifier to dirty old trans fluid. If you don't know when it was changed last then I'm sure it's time. Me I always do a complete flush followed by a filter change. Good maint in my opinion fixes a lot of issues. Good luck. Keep us posted on what you do

Jet A-1

I should have followed up here sooner. The shuddering I was experiencing was indeed the plugs. I should have taken pictures to show but the gaps on the old plugs were easily twice that of the new ones! It's a wonder it started at all. It runs with a whole lot more get up and go now.


Having said that I'm going to get the trans fluid and filter changed before towing season gets in full swing.