While going to pass another vehicle a few nights back, my truck did something that gave me a pretty good scare.

I was doing around 60mph when a slow-moving vehicle pulled out a little ways ahead of me, so I let off the gas for a few seconds until an oncoming car went buy, then I floored it to pass the car. Well, normally the truck just downshifts and I can pass with ease. Not that night...it didn't downshift, just seemed to bog for a few seconds (3-4 seconds), then it did a made a really nasty clunk and finally downshifted.

I wanted to make sure it wasn't a fluke thing, so I tried it again yesterday...same situation. It won't happen if I'm already on the gas and then pin it, only from no throttle to full. And it only happens when I'm cruising above 57mph. I was already driving for around a half hour when it first happened, so the truck was up to normal operating temperature.

Not only is it a horrible clunk noise (that you can feel throughout the whole truck), it scared me because I didn't know if I was going to be able to get around the car I was trying to pass. It bogged for a good 3-4 seconds before it made that horrible noise, and eventually downshifted.

So is this a known problem? Has anybody else experienced this? The earliest I can make it to the dealership is next week...so I won't be able to have it looked at until then. I'm just a little nervous because I'm making a trip to the dunes this weekend (4 hour each way) pulling my quads (around 4000lbs). I picked this truck up because I didn't trust my old F-250 with the 6.uh oh anymore...the last thing that I need is another one to worry about.

Oh yeah, it is a 2010 Lariat with the 5.4 if that matters.

 

There is a TSB for a harsh 1-2 upshift, harsh 2-1 downshift. A harsh downshift into 4th gear at highway speeds 45-70 MPH.

My truck has done the harsh downshift to 4th gear 2-3 times in 22,000 miles. I haven't had an opportunity to take mine in yet. This sounds like what you might be experiencing. I would have the dealership check to see if this TSB pertains to your truck.

 

Mine has done this and it feels terrible.

 

The first time mine did this, it shifted so hard that I thought I had just been rearended.

 

Are most of you experiencing this problem with the 6sp trans or is it a problem with all? My 09 has the 4.6 2v and 4sp tranny with 28000 miles and it's always been sluggish to down shift. Seems like I have to floor it to make it happen. If I'm trying to get on a highway and I need more speed I have to stomp on the pedal or it'll just stay in the gear it's in and take forever to accelerate. Today I needed the extra go power to pass a slower vehicle and it dropped gears hard. It made a bang and it felt like something hit me from behind. Is the TSB for the 4sp tranny also?

 

idk but i have the same truck as you and i have the same problem

 

My tranny has the hard 1-2 shift, plus the shift points are too low. Feels like it's slipping too. I get three nudges when I come to a stop, a thump when I take of from a stop and shutter at 40 mph. Truck is currently in the shop and I'm told their replacing the PCM (second time replacing it) because it won't accept any programming. Gave them two TCM numbers on tranny issues when I put the truck in. Currently the 4th day it's in the shop.