This is for the land cruiser since not a lot of activity is seen on the LC page, you still might be able to help. Started about a year ago and has continued to get worse. When you hit a bump going any speed above about 30 (like a highway overpass or a crack in the road) the whole car starts to shake violently. If you arent paying attention or you have one hand on the wheel it can be a big shock and the car will try to dart one direction. This typically happens more when the right front wheel hits the bump but still happens with either side. I had the dealer take a quick look while i was getting an oil change and they said nothing looked out of the ordinary but something is obviously wrong.....Any insight?

 

May be a few things but I cant say just one. Alignment would be my first guess. My chevy has a similar problem but its when I turn one way it sometimes turns very sharply with ease because of the pore ability to align the thing. Maybe bad axles? Cant really say for sure. someone on here may be able to help more

 

Sounds like a rack problem...buishings,inner or outter tie rods maybe?

I would check here:http://forum.ih8mud.com/
http://forum.ih8mud.com/100-series-cruisers/

These guys are all about landcruisers and Lexus SUV's.