well I have a 98 sidekick 2wd, roadmaster baseplate, towbar, etc. we hooked up and took off-- looking in the back up camera I saw the front of the kick go to the right then to the left, I stopped and did this again with someone outside looking. sure enough the front wheels went left the right over and over, with a lot of violence, bang-bang-etc. I had the front end {toe in -out] adjusted, could this be some other adjustment?
thanks
larry

Tow bar level?

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tow bar have any slop in the connection allowing sidekick to drift left and right?   it shouldn't.   

If it is tight then you have some loose steering components or bad front tires?

I assume you left the key in the position that the steering column was unlocked.  If you don't you can have this situation.

u mean if the tow-bar is not level it will this?

everything seems to be correct with towbar height,tire pressure, toe in/out, I heard about caster?

 Yes , if the caster is off it will not tow correctly.
Here is an old trick:
 Take 2 bungee cords hooked to the steering wheel. Pull one out the passenger side door and close the door on it.
Do the same on the driver side.
The idea is to mimic a light hand on the wheel as if you were driving rather than towing.
 You don't want the cords super tight  but they must have some pressure.
Try towing again....