Hello all,
I am in the first weeks of ownership of a 2012 F-150 XLT Supercab with the 3.7L V6 (or as I call it, the baby 6). I have been noticing a rather disconcerting "thump" 1 or 2 seconds after the truck stops. I understand that this model comes with hill start assist or something like that, and was wondering if that is what I am hearing/feeling, or if this is something else, like maybe the transmission making that final downshift into first. The only reason I even thought about the latter is that while I am braking, the gear display will drop steadily through the gears to second, but never seems to downshift to first, no matter how slow I get.
Any ideas?

 

Well, in my truck that thump is one of the water bottles rolling around in the bed. But, I'm guessing you have a driveshaft thump that is famous in this gen. Search for "slip bump".

 

Spiky, It's my understanding this bump happens coming to a stop or when taking off, like rolling forward. Is this correct?
I sometimes get a double bump while stopped and I don't know if it's this slip bump thing or something going on in my trans? Torque converter sticking? I just lubed the slip with the Ford grease like 6 months ago. It rarely happens, but when it does, I am not moving at all.

 

Yeah, I am not moving either. However, I think Spiky might actually be onto something. After reading through several of the threads that were returned from a search on "slip bump" not only am I noticing my original THUMP but occasionally some of the others that are mentioned. I had the really hard/stiff downshift on a hilside with a bit of a load on the truck about a week after I got it.
Sometimes its better NOT knowing whats going on....
However, somthing "interesting" going on with the torque converter in the transmision would explain it.

 

The abrupt downshift is the lead frame on the transmission. Depending on the year, there is an "extended warranty" service on this. If it was downshifting somewhat hard while loaded downhill with your foot off the accelerator, this is pretty normal as the truck is trying to use the gearing to slow you down. Not sure if you know about the speed sensor/lead frame issue, but do a search on this one. There's a re-flash available with replacement of the lead frame if you encounter this issue after a re-flash.

The issue I have with this bump "while stopped" being diagnosed as the slip yoke, is that's part of the driveshaft. So if you're not moving and just sitting there, why would you get a bump without moving? To me it feels like something that's supposed to be disabled when idling is not, like a torque converter or clutch plate sticking or something.

 

Yeah, I guess that might be a second too late for the driveshaft bump. If you have a lot of hard shifts, try resetting the KAM by unhooking the battery for 15m. Maybe checking the oil level would be good at this point.

 

Yeah, I was aware of this issue, and need to swing by the dealer to get it taken care of. Planning on trying to get that done next week at the same time as I get an additional key, and the current one reprogrammed -- I am the 5th owner apparently, and I have no idea where the missing key went.

 

I'd bet a cold soda on the thump being the slip yoke. I've had them bump after coming to a complete stop for a second or more. As a test measure, sometimes you can induce the bump. After coming to a complete stop (assuming it didn't bump) shift into neutral and see if it bumps when you do that. Or just pull the shaft and put a good synthetic assy lube, or NeoLube on the splines and see if that fixes it. I think it will.

 

I agree 100% (he beat me to it). I had a "shudder" only when coming to a complete stop; or when taking off from a dead stop. It never happened at other speeds.
it was minimal... but when you spend $20,000 on a 100,000 mile vehicle.... you tend to be "picky".
I had the service manager take a look; he agreed it was slip yoke related.
He kept the vehicle; called me the next morning; and the shudder was gone.

I believe it goes dry after some time.
I may have only been lubed (a temp fix)... but it is fixed for now.
He mentioned something about it being a "two-piece" driveshaft... not sure if that matters.

Best of luck!

 

Now you make me wonder what I really got into -- I paid 16k for a truck with just under 57K. Either I got a really great deal, or I bought somebody else's problems.