germanshepherd

this just happened recently. when I accelearte from a dead stop (and only when cold, that initial taking off after truck was sitting for a while) I feel and hear a single thump sound. I can stop and go after that and it does not do it, only the initial time after sitting for a while.
I searched and searched and seeing about the yolk/driveshaft thin and torque converter shudder. From what I read, the shudder is typically not a single thump but more of several in rapid succession?

the odd thing is is that it does not do it after I am already driving and stop and go. any ideas what the issue may be and why it does not do it after the vehicle is warmed up or even just driven for a few minutes when I stop and go? it happens within a second or two of accelearating and not gunning it, just a slow acceleration.
thanks

Hootsworth

Does the thump/thud feel like it's coming from behind you? Also, is it accompanied by a 'bump' feeling when accelerating? If so, your Slip Yoke probably needs to be greased. This is a VERY common issue that happens.

Just grease your slip yoke with teflon grease and you should be good.

Edit: Just to throw in my anecdotal evidence. My truck when I first got it had a very pronounced "bump" when taking off from a dead stop. It would ONLY happen then. The bump felt like it was coming from the drive shaft somewhere behind me. Once they took it in and greased the slip yoke, it went away completely.

germanshepherd

Hi. Hard to tell where its coming from. Will try to narrow it down. If it is the slip yolk, why only when truck was sitting and I accelerate but as soon as I stop and go again its fine. Odd

homer

Hard to say but the first thing that comes to mind for me too is you're getting the slip-bump issue (common on crewcab). Is it a crewcab you have? That would be my first place I'd start though. Hard to say why it's only after sitting.. could be the existing grease warming up but it's really hard to tell. For the cost, I would try greasing the slip yoke though.

germanshepherd

Hi. It is a crew cab.

homer

Here, I've posted the TSB for you. Hopefully that helps.

Hootsworth

I couldn't tell you the exact reason why, but mine was the same way. When I took off from a dead stop, I would get the "bump" behind me. If I had ANY momentum at all, I would not get it.

I would recommend greasing the slip yolk first. It's cheap and something you can do yourself to make it even cheaper.

homer

I agree, it's honestly not a very difficult job to do at all! Could probably do it in under an hour. Make sure to use the e-brake or block the tires for safety of course (you may already know, I just like to point it out ).

germanshepherd

appreciate the tips and TSB info. getting frustrated with this truck. I love it but its also driving me nuts. I got it 3 months ago and nothing but problems with it. now the HVAC system is acting up. makes the grinding squeaking noise when switching from vent to floor or defrost. sounds like piece of foam or something stuck in there. that will go to the dealership or my mechanic and I would not attempt to remove the dash which seems like what is needed to get back there.
its not the blend door since the temp control works fine when changing from cold/hot etc, just the diverters or whatever they are called that sends air to the vents, defrost or floor etc. thats another story. sooner or later everything will hopefully be to where I an enjoy the damn truck.

lewissa81

It sounds like you have a lead on fixing your initial issue, so I'll try to save you some money with your hvac issue.
Don't take your truck to the dealer to take the dash off, they will charge an arm and both legs. You may be right about a piece of foam blocking the mode door. You may also have a bad mode door actuator. Dirttracker18 did a nice little write up on getting the foam out:
https://www.f150forum.com/f4/stuck-v...-guide-277402/
It's quick and easy to do, so don't get intimidated.