Thump when stopping and sometimes when taking off

[Ellison Brown III]

My 2011 XLT (175k mi), which I've only owned for a couple of months, has a pretty consistent 'thump' (it's somewhat muffled or muted) when coming to a stop, and only happens just as the vehicle has quit moving (not as you are slowing down). It's just one single thump that you sort of feel in the floorboard, no other lurching forward or late downshift type of sensation at all - just the thump. It will also do it occasionally when taking off from a stop, too. Just as you are taking off. Same thing - one, single thump.

I thought it could be the 'slip bump' thing, so I removed the driveshaft and greased up the splines with a PFTE grease, but it seems to make no difference.

I'm assuming I'm not the only one with this symptom, so I'm hoping someone here has some ideas! Thank you, as always!

Driveshaft was my thought as well. Had that issue with a truck before. But it’s not your problem; wonder where your issue is stemming from.

 

[Bolt snapper]

Yeah, I'm at a loss. The transmission mount could be the problem, but I almost think no. I'm not even coming in for a stop in a hard torque condition when it happens. I brake for two blocks like the old man that I am and unless I completely release the brakes just as I stop, it's gonna do it almost every time now. And a sound / feel like that that comes through the floorboard could be coming from anywhere - front, rear or middle. My rotors are slightly warped, and I'm wondering if that isn't what's going on: The brake pads are shifting at the stop due to the slight change in the rotor shape right at the stop. I'll probably see if they can be turned, since rotors are insanely expensive for these trucks.

 

[thereheis]

Following. 2010 Expedition King Ranch doing the same thing.

 

[Fastcar]

Yeah, I'm at a loss. The transmission mount could be the problem, but I almost think no. I'm not even coming in for a stop in a hard torque condition when it happens. I brake for two blocks like the old man that I am and unless I completely release the brakes just as I stop, it's gonna do it almost every time now. And a sound / feel like that that comes through the floorboard could be coming from anywhere - front, rear or middle. My rotors are slightly warped, and I'm wondering if that isn't what's going on: The brake pads are shifting at the stop due to the slight change in the rotor shape right at the stop. I'll probably see if they can be turned, since rotors are insanely expensive for these trucks.

Usually if you feel it in the steering wheel it's a front suspension issue. Under your ass or feet rear end/drive line issue. But.. as you just described sounds like something is unloading. Have you gotten under it with a bar and a light to check for anything loose?

 

[Bolt snapper]

I've crawled around with a light and pulled on things with my hands - haven't used a prybar. I'm not sure where I'd pry? But you're absolutely right - it is under the floorboard (not through the wheel), and that's the best description: unloading. One out of every twenty times, you feel it a little on takeoff, too, but not as predictably. It's almost every stop

 

[Fastcar]

Try this. Start it up, put it in 2wd, One foot hard on the brake, one foot on the gas, Hard on the gas and then quickly off the gas see if you feel it. Not just a little blip on the gas pedal, bring it up to stall.
Do this outside away from people.

 

[Gussy-Larry]

I would check the rear diff support bracket. There is a bushing in it that wears out and causes the thump. FordTechMaculoco has a video on how to replace it.