Rotating the Driveshaft?

[SCAR911]

Well every video of every tech I watched on how to replace the pinion seal all marked where the drive shaft connected to the flange and marked where the flange went into the diff, so that's what I did and I have zero issue. Maybe it's a myth and maybe not, but it takes seconds to mark to make sure you won't have a weird issue.

 

[Domin0]

Got under the truck this afternoon to see what I could do. Ended up lubricating the slip yoke, which I’m glad I did, and rotating the driveshaft clockwise twice in 90° increments. I noticed changes in the speeds at which the vibrations seemed to occur, but no solution. Ran out of daylight and willpower, so I’ll perform the last 90° change tomorrow.

Under light, I also noticed that there was some light marring left by the shop that dropped the driveshaft, seemingly from whatever tool they used to remove the bolts. I wouldn’t think something so minor matters, but don’t suppose this would have an impact on anything?

 

[New recaros]

90degs twice? You’re right back where you started.

 

[Domin0]

90degs twice? You’re right back where you started.

 

[RogueClimber]

90degs twice? You’re right back where you started.

 

[Highwayman]

IMHO you're chasing your tail.....

Thats not damage in the picture and would have no issues with balance, its cosmetic.... If there's not dents or dings, its fine. DS are a balanced assembly and the F150 assembly line doesn't do some super special procedure throwing it on, I can guarantee that. Marking the DS is done if you actually SEPARATE the DS by putting new U joints in and not just slipping in and out of the truck.. Think of it as a wheel and tire its balanced, it doesn't go out of balance or suddenly cause a vibration because its not 100% bolted back up to the hub in the original position it left the factory.

If you want to stop running in circles and need confirmation, pull it and take it to a driveshaft shop.... They'll tell you in 5 minutes if its out of balance.

 

[New recaros]

Just go 90deg’s as FT1 stated.

 

[New recaros]

View attachment 446027

I know what you’re thinking, but 90 deg’s is the correct amount. 180 deg will just cause the vibration again. It does sound stupid. Guess I need to write better.

 

[Domin0]

I know what you’re thinking, but 90 deg’s is the correct amount. 180 deg will just cause the vibration again. It does sound stupid. Guess I need to write better.

Last rotation to go would be the same as a single 90° turn in the other direction from where it started, so that’s my last bit of hope before considering @Highwayman ‘s suggestion.

 

[Domin0]

Making a fool of myself here, but hopefully it helps someone else in the future if they find this thread. Per the dealership, their senior master tech was unable to identify any issues with the driveline, and pointed to "heavy cupping" of the OEM KO2s as the cause. Prior to this, I had the tires RF balanced as soon as I felt the vibration as a means to eliminate them as a possible source (it didn't help), and did not even know that cupping was a thing. Based on a few other threads, this doesn't seem like an uncommon issue, and after dropping the PSI from 38 to 35, I've definitely noticed a reduction in the vibration at all speeds.