This problem is on my 2006 F350, 6.0, 4x4. Bought it last month.
95% of the time my alignment is spot on- barely have to touch the wheel. Occasionally, it will start to pull to the drivers side. As I correct, the tension increases in that direction until something finally gives and it "jumps" back to the passenger side. I replaced both tie rod ends a few days ago and that made the jump less severe, but the underlying issue is still there. When I feel this problem starting and I'm at low speeds I can yank the wheel to the passenger side and stop it. I can't find anything on here, or elsewhere, that matches this description.

After tie rod ends my next theory is worn ball joints, but I want to vet the theory here first. I'm thinking the worn ball joints allow the wheel to camber out slightly (maybe when I hit a rut/pothole/bump/etc.), and it continues to give in that direction until it reaches the mechanical limit, then jumps back to realign with the trucks forward movement. I jacked up both sides and tried to rotate the tire back and forth vertically, but couldn't make it happen (used a tire iron and then a 2x4 for leverage). I may be way off here.

Has anybody encountered a similar problem? The guess-and-check game gets expensive pretty fast, so thanks in advance for any help.

 

Front axle U-joints. When they start to intermittently bind, they cause exactly what you are describing. The symptoms will slowly and gradually get worse to the point you will not feel the truck is safe to drive.

Word of caution, they will likely not feel like they have excessive play. If you take it to a shop and ask them to check the U-joints, they will pry on them to see how much play they have. In order to properly diagnose this failure mode, you have to pull them out and inspect the needle bearings under the caps.

 

Thanks Thomabb-

I replaced the drivers side U-joint yesterday. The needle bearings in 2 of the caps were corroded and crumbling. Never done this before- the link below made disassembling/reassembling a heck of a lot easier, despite the differences from '04 F250 to '06 F350.

2004 F250 Ball Joint Replacement

I'm on the road for work, so these were far from ideal conditions. I'd love to wait until I get home in a few weeks to replace the passenger side front axle u-joint. I'm guessing it will be in similar condition. Anybody know if that is ok, or is replacing 1 of 2 bad front axle u-joints and driving around for a few weeks a really bad idea? I'll post in a couple days with an update on whether this cleared up the steering drift and jerk problem. Either way, replacing the front axle u-joints needed to be done- thanks again.

 

Update - It's been a few weeks - still holding strong, no signs of the problem described earlier. Replacing the u-joint did it. Thanks thomabb- owe you a beer.

 

Glad things worked out. Thanks for reporting back.

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