Haha, it's easier for us to sit around talking about it that to actually check I guess. Based on jastutte's observations I'm guessing that either there's slop in the motor to seat drive interface, or the motor itself isn't secured properly. It definitely weird when you're not ready for it and it shifts just slightly without hitting the stop. That weightlessness moment messes with the inner ear.

Funny side note. A few months ago I was under the truck and noticed a gnarly-*** pair of vice-grips still clamped to the one nut that's not captive on the driver's seat. Probably been there well over a year, since I was trouble-shooting a non-heating seat heater.

 

I forget about it until I dont. Then remember I need to take a look on the weekend. Then get busy and forget about it.
Now this thread comes up to remind me, but I dont have a free weekend, so if it slides too far, I will forget to check again next weekend.
The cycle of little fixes.

 

My rocking seat was caused by a broken plate on the seat motor. With the damaged plate the adjusting screw has play. I couldn't find the actual photo so I got this one from the google.

 

I'm thinking my issue is related to the motors/mounting brackets or related parts.
thanks for the photo.

 

I had this many times in an old '04 I owned. Luckily I bought an LR extended warranty for the truck at the time. Each time I brought it in, probably 3 times, the dealer had to replace the seat frame because a weld had cracked, at least that's what they told me. I'm sure this is the same issue that everyone else is having. It's not the bolts. Inspect the frame if you want to fix this. Hopefully it's not a hard fix if you know how to weld.

 

My passenger seat does this, Im pretty sure it's from my daughter kicking the back of the seat over the years.....maybe I'll pull it out someday and look? On the list that seems to be getting longer these days....

 

so, this was the issue. the plate broke off and the screw shaft had fallen at an angle to the floor board. that is why the seat was rocking at the front up and down. i moved the seat forward to take off the plastic finisher peice on the side of the seat and then when i moved it back the the screw shaft wedged against a screw/bolt under the seat keeping it from moving back all the way.

today i lifted up the seat cushion and ziptied the top frame to part of the side frame. this keeps the front of the seat from rocking up and down but allows the seat to be moved forwards and backwards.

i can post photos later of the zip ties if anyone wants to see the hillbilly fix.