Hi, everybody!
Just want to share some experience about vibrations in LS400 93'-99'. I'm a long term owner of LS. My first Ls was 93' and it had a problem with vibrations of all body. Sometimes it felt strong, sometimes it almost gone. I couldn't figure out the case of this problem for a long time. Suspension was replaced, tires was new, engine and transmission mounts was replaced. Sometimes it felt like misfire. I dig in to the engine. Suspected a compression problem, Injector problem, transmission problem, but everything was wrong. Vibration was there. So finally i give up and sold that car. Later I got another LS400 97'. Everything was in perfect shape except once again sporadic vibrations. I used it only half a year and sold it again because of that unresolved situation. Than I found a LS400 99' with 130,000 miles on it. It was in perfect condition Cali car. No rust at all. Leather almost like new. And..... No vibrations. But because some changes in my life my car stayed in the garage for 1.5 month and then I run a trip right across the all states to NY. 3000 miles - no joke. What happen in that trip I will remember forever. Because just after maybe 500 miles I began to feel aaaaa VIBRATIONS. The same as in my previous cars. And after 2500 miles on the road it became really severe (by the way my car was fully loaded). But I was lucky to reach NY safely. And I began to search. So the cause of all this bad vibrations was a driveshaft. It is a combinations of factors. First I guess usually the vibrations produced by worn or broken tran. mount or engine mounts. After that if nothing was fixed immediately it creates a really big load to the U-joint of driveshaft and driveshaft begin to vibrate by it self. So even after change of faulty mounts the vibration will be present.
So guys if you feel the vibrations of body, on the steering wheel, when the engine cold and you just started driving or as usual 40 to 60 mph it is a really big possibility that you have damaged U-joint. First check your engine and trans. mounts. Second try to check U-joint. The driveshaft by it self really expensive part but it makes a big difference. No more vibrations at all and problem finally solved. Hope it will help to somebody.
