Thump when stopping and sometimes when taking off

[Bolt snapper]

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!

 

[Fastcar]

Might be a engine mount or trans. mount.

 

[Dennis_H]

Might be a engine mount or trans. mount.

That's where I would start. Have had that with a transmission mount that was bad. Also check bushings in suspension. Son's F150 (yes completely different suspension) had a bad leaf spring bushing and it felt just like that. May be a control arm bushing on ours.

 

[Bolt snapper]

That actually makes a ton of sense, especially after looking at the design of that mount. I'm wondering if it can be "buffered" by filling it with polyurethane sealant, strips of rubber, etc., without having to replace the transmission mount right away?

 

[Yupster Dog]

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

Check swaybar and end links.

 

[techdude99]

Agreed. Common issue with loose swaybar ends link bolts and sometimes the related bushing "D" clamp bolts. Check with a torque wrench.

 

[Dade34]

There's also a known issue with the lubrication of the drive shaft spline going into the transfercase/tranny

 

[Tradman2018]

Yes- My 2013 F150 had the thump too. Almost always happened upon coming to a stop. I read on a Ford forum that it was a well known issue that essentially stemmed from the drive shaft having an occasional tendency to bind where it came into the transmission or another location and would thump/pop. There was a bushing kit to alleviate the problem but I just put up with it. May or may not be the OP's issue.

 

[gimmesomecoffee]

Observe underneath the car while somebody in the driver's seat holds the brakes while shifting between drive and reverse. (to calm your nerves, chalk the wheels or raise wheels off the ground)

I had the infamous rear diff mount thump that was very similar to what you described. Relatively easy/straightforward fix.

 

[Dade34]

Here's a good video on the drive shaft fix
https://www.youtube.com/watch?v=0jT4qnPFCs8

 

[BlackBetty]

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.