Dr_Nelson

I just recently got this 2013 F150 XLT 3.7L 2WD. Now, I noticed these intermittent vibrations. They feel like driving over highway rumble strips and last for 1-2 seconds max. They come and go both in the city or on the highway. Most of them seem to happen around 1600 RPM.
I suspected any of my three u-joints on my 2-piece driveshaft, or maybe the center bearing. But those look and feel tight. But it seems that I have play in the transmission output shaft. Very similar to this guy: If I take my hand and wiggle the driveshaft, I can feel and hear that there is play in the output shaft while the U-joints seem ok. Also, the output shaft and the u-joints are bone dry, no leakage at all, which makes me believe that the output shaft seal is doing OK.

Questions:

1. Does play in the output shaft cause that kind of intermittent virbrations?
2. Does this fix include parts that can be replaced without taking apart the transmission? E.g. a bearing that needs to be pulled out?
3. Has anyone done this before?

I am planning to replace all three u-joints and grease the slip yoke anyway, just waiting for it to not rain or be not that hot.
And my apologies if this had already been covered in another post. Happy to look there if you point me there; couldn't find anything.

Any feedback appreciated!

Dr_Nelson

Anyone?
Or how can i move this thread under "Engine/DriveTrain Talk"?

Barry_Vee

I have not pulled trans yoke on 6r80. Know little about them. But...Maybe some old school observations can help.

You may already know all this. Driveshaft yoke typically slides through an oil seal and bushing style bearing and onto a splined tail shaft (with a sloppy fit) inside the back of the transmission. What keeps it spinning true is the bushing, and to some extent the oil seal. Oil seal will go out after excessive bushing wear leads to excessive yoke wobble. When that happened I’d change just the oil seal until that became frequent and then the bushing too. Let it wobble long enough and the bushing will eat into the yoke requiring replacement of it too.

Before Changing anything maybe pull the drive line, check U joints real close, inspect yoke-bushing bearing surface, grease the spline inside the yoke, put it back in and see if anything changes. (Mark the driveline so it goes back in how it came out).

Oh, make sure vehicle isn’t parked with the front up hill or tranny oil will pour out when the yoke is removed. Be ready for that anyway.

My bet is on the driveline steady bearing though.

Dr_Nelson

Thank you Barty_Vee!

The auto parts store only had two of the three u-joints. I went ahead and replaced the front and rear. Part for center comes
Monday (i have a 2013 XLT RWD with the two-piece driveshaft). Truck has 145k miles and they looked factory.

one of the u-joints had this plastic worn out:



Should look like this:



I took her for a test drive hoping there wouldn’t be any more intermittent vibrations, but it still was there.

i may end up going to ford and have them look at the output shaft bearing and get it replaced as I don’t know how to do that. Just looking at the output shaft i have no clue where to even start:




And it definitely has audible and feel-able play.

First, i am going to replace the u-joint at center bearing first, although I don’t think it will eliminate the intermittent vibrations.

Barry_Vee

Glad you found & fixed a bad U joint. Looks like your output shaft has a bolted flange vs a sliding spline and that makes absolute sense for a two piece unit now I think about it.

When an axle moves up & down driveline length increases/decreases to accommodate for the dimensional change. That is what the sliding spline is for. I forgot with a two piece driveline that sliding spline is associated with the rear shaft. There might be a boot over it too.

Here is a picture of my one piece driveshaft where it enters the transfer case. The yoke (rusty part) simply slides off a splined output shaft once the driveshaft is disconnected from the differential. Looks like your front yoke is attached to the output shaft with a nut. The shinny black and scrubbed looking rust portion at the oil seal is What slips in and out as my axle moves up & down.

Cleaning & lubing the spline with grease can solve clunks and vibration problems.

Dr_Nelson

Yup, exactly. The boot is roughly in the middle, close to where the center bearing is. As you can see, it was not bone-dry:



I cleaned and greased the yoke with this teflon lubricant, but intermittent vibration is still there (not as frequent, though. So, i assume replacing the bad u-joint has helped a little).


I did not use this toothbrush after in my mouth

Dr_Nelson

Does anyone know what size the Output Shaft Flange Nut is?
And do I need a special socket for that or will a 12-point deep socket do?
(see item #1)

Dr_Nelson

OK, I am buying a micrometer/caliper to measure that nut.

Joah52683

Did you ever find out your problem? My truck does the same exact thing. I have the same truck and can not figure out what is causing the vibration.

tmitchell009

Check your u joints.