Thud under gas pedal when taking off

[jking05]

When I come to a stop and then hit the gas I can feel a thud coming from right under or behind the gas pedal under my feet. It doesnt do it every time but most of the time. Of course the dealer couldnt replicate it but wondering if anyone else has it or knows what it might be? They said they checked the suspension but everything was good.

 

[Wayne Decker]

The engine starting back up?

 

[aggiegrad05]

The engine starting back up?

(This was my thought initially too)

 

[jking05]

No the engine is running. When im at a stoplight or stop sign it does it when taking off.

 

[aggiegrad05]

Yes, but when you come to a stop your engine is going to shut off. And as soon as you lift your foot off the brake, it is going to start again which causes a slightly noticeable nudge in the pedals.

 

[Deadman]

Thats that stupid auto start stop

 

[Cigarguy]

I get the same thing. It’s most definitely not the auto stop/start. I spent 12 years in the car business. Many of those as a service manager. The auto start is blatantly obvious. This is more muted than that and feels like someone tapped the floor once with a rubber mallet.

 

[Wayne Decker]

Did you run over someone who was carrying a rubber mallet? Just a thought.

 

[Deadman]

I get the same thing. It’s most definitely not the auto stop/start. I spent 12 years in the car business. Many of those as a service manager. The auto start is blatantly obvious. This is more muted than that and feels like someone tapped the floor once with a rubber mallet.

I deleted my auto start stop junk so I don't know what that crap even feel like anymore! lol

 

[NukeLife]

Yes. I’ve felt it every so often. Very distinct solid mechanical thunk. My dealership couldn’t replicate it either. I’m leaning towards a torque converter issue.
Maybe it would be easier to replicate pulling a trailer? More load on it?

 

[osteodoc08]

Engine or transmission mount?

 

[jking05]

Exactly its not the auto start stop. My engine doesnt always shut off when I stop and its obvious when it does. This happens with the engine running and it does feel like a rubber mallet tapping right under the pedal when you take off.

 

[duneslider]

Does it do it in 2h and 4a? Just curious if it is maybe a drive shaft clunk. Usually it isn't noticeable but sometimes there is enough play to get a clunk.

Could be a loose mount too, engine or transmission. (This would surprise me on something this new)

If you start rolling without pressing the gas pedal does it still do it? Or just hitting the gas from a stop?

 

[jking05]

Its 2WD. Just hitting the gas from a stop and it doesn't do it every time. It almost feels like something is catching right behind the pedal and slaps the floor when its pressed down more.

 

[Deadman]

Its 2WD. Just hitting the gas from a stop and it doesn't do it every time. It almost feels like something is catching right behind the pedal and slaps the floor when its pressed down more.

Floor mat? rubber boot?

 

[Cigarguy]

I almost liken it to slight play in a driveshaft that gets bound up when torqued (if that makes sense).

 

[firstford]

I have the same thing, funny if you ask the dealer they say, we can't reproduce it and this is the first time anyone complained about it.

 

[Andrew Roth]

I have a 2017 F150 as well with the same power train (gen2 3.5 w/10spd) and it does this thud too when you first step on the gas. I will describe it like a loose tennis ball in the bed of the truck. Bouncing into the tailgate on accel. I even had to get out and look and see if I had something loose rolling around. Kind of seems like it might be related to the front suspension becoming unloaded on accel.

 

[Artie]

I almost liken it to slight play in a driveshaft that gets bound up when torqued (if that makes sense).

So possibly a u-joint? Did I just date myself with that... I assume they still use those but what do I know.

 

[Soliyou]

This is not the same generation but could be a similar issue: