Hey folks. I have this issue where my 2011 Eco S/Crew feels like it's being rear ended during the warm-up / driving period. Generally as the tach starts to fall to normal operating rpm's during cold weather, the truck will feel like it's being slightly rear ended 3 times in a row with about 1 to 1 1/2 seconds apart. Always 3 times. Also every winter since I've had it. I've had it into the shop and of course they can't replicate. Anyone have any idea as to what might be causing this?
Thanks for your help!

 

Have you regapped your spark plugs? A lot of people have tightened the gaps down to .030 on the 2011's and they seem to run smoother.

 

No, I never thought to do that because it feels like it's coming from underneath or from the rear. I didn't think that the plugs could cause it. It happens at a complete stop. Usually at a set of lights. Once it happens, it won't happen again until the truck is cold and I have to stop at the right time it seems to do it again.

 

Transmission. I had one replaced a few years ago that was doing something very similar.

 

why not leave truck at dealership for a night or two and let it get cold then go and start it with mechanic sitting in truck and see if you can replicate issue while truck warms up from the cold start.

 

I have the same issue with my '12 FX4 and I'm pretty sure it's part of the TSB that lubes the slip yoke in the driveshaft. Going to have it done on mine when I take it in for the oil change. Also going to have them reflash the trans ECU because I'm having some hard up shifts and down shifts.

Do some research on the slip yoke TSB, can't remember what the TSB number is. There are plenty of threads on this site about it.

 

I checked out videos for the slip yoke. I don't think that's it. The vehicle is always at a complete stop already when my banging happens. In the videos it looks like the slip yoke clunks when coming to a stop. I'll have to get really good at replicating it so I can take it in.

 

I'm having the same issue. It happens when it's cold. Once it's warmed up it's fine. It feels like the pressure in the transmission is rising and falling really fast. I wonder if it's a selonoid sticking until the trans fluid warms up?

 

I logged in here tonight getting ready to post about something "similar" that mine is doing (first winter for me with my '11 ecoboost). I live atop a large hill. It's a 1.5-2 mile downhill grade before it levels out. During the summer I just pull out of my drive and coast down the hill in 6th gear at 50-55 mph, very low rpms and tap the brakes if I need to coast slower. If I want to go 35-40 mph, such as if there are school buses around or something, then I will click the TowHaul button and it will typically drop the truck into 4th, sometimes third, jumping the tach up toward a steady 2000 or 2500, steady. With this cold weather here in NY my truck is now acting funny when it's cold. It will not coast down the hill steadily. It wants to jump around between 3-4 or 4-5 gears and even if I lock it in a gear, either manually or if I just lock the higher gears out then what it does is it keeps "surging" of sorts. The tach jumps up and down, fluctuation 200-300 rpms every few seconds. Sounds like the truck is almost skipping, but it isn't. It's running smooth. Touch the gas and it's perfect, turn around and drive Up the hill and it's perfect. Do this 2-3x and get it good and warm, and it's perfect again. But driving it cold....it's not right. Going to call dealer Monday.

 

My bad then, mine happens right before I get to a complete stop. Feels like someone bumps into my bumper, kind of "bumps" the truck forward before I stop completely. Pretty sure my problem is the slip yoke thing. Didin't notice that you said it does it while you're already stopped.