so me and my little brother went to go pick up a 93' LS400 for him yesterday, the body and paint is still good conditions, interior is ok and engine seems good. the previous owner did told us it needed some work, basic tune up and motor mounts. if you drive the car under 30 mph it'll be smooth but once you go over that speed limit it starts to vibrate and if you go around 50-60 mph it'll vibrate like crazy. does this sounds like a bad motor mounts or something else? one of my buddy test drove it and says it's not the motor mounts but maybe the tires, brakes or something else instead.

 

wheel balance.

 

wheel balance or bent wheel

 

I had a tire that was fixing to go out and it would vibrate at around 50+. I thought it was a bushing or somthing. Went to check and the tire was coming apart on the inside.

 

As everyone else is saying, wheel balance. Is "peaceboi" your bro? If so, I was gonna post in his thread but he said it ran rough with the shake. Also says the steering wheel doesn't shake so it could be a back tire unbalanced. If it was a rotor then you would feel it at any speed. Probably not the motor mounts but you can test them by putting the car in drive with foot on brake, give it some quick gas and see if the engine moves a little or ALOT. Also try it in reverse. A bad tranny mount will cause vibration. You can do a search on that and there is alot of info on it.

 

yeah peaceboi is my little bro. i didn't know he made a thread as well haha. anyways i don't think unbalance wheels will cause this much vibrations, i mean it's like having a very loud sound system in the car and feeling the hard bass kicking non stop, and that's really how it feels like. but i'll try that stepping on the brakes and giving it gas. i was also thinking it could be the transmission mount b/c i know the SC300 has similar problems w/ a bad transmission mount.

 

could it also be a bad driveshaft?

 

My car is doing the same thing.. Changed my wheel bearing n the tires were all balanced when I put it on n it was fine but after a while it started again.. 0-45 is fine but I would say it starts around 55 where u can feel it.. At 60-70 u feel it like crazy n u don't really want to drive faster than that because it feels scary.. I thought it was my front stacked wheel spacers causing it.. Lifted up my car the other day and my tie rod was loose n the rear bushing had very little play so imma try to fix those n maybe try an alignment since my cousins GS started shaking all crazy n he did an alignment after we lowered it n it went away

 

^Was just gonna say.

Check tie rods and tie rod ends.

 

Odds are it is something related to the wheel or bearing. Unlikely anything to do with the drive shaft or engine. If it was, would do it at say 20, 40, and 60 as it hits the same revs in each gear.

 

It could potentially be a drive shaft center bearing.

 

sorry no updates b/c it's been way to cold to be outside...

 

Quick Update: so i took the car to 3 different shops in they think it has something to do w/ the tires/wheels. so i let the 3rd shop do a 4 wheel balancing on the car...but it's still vibrating. i'm gonna take it back to them to see if they can diagnose the real problem. my coworker says it sounds like a bad tie rod b/c his car used to have the same problem i'm having.

 

New Update: ok so i took it back to the shop and they think they have found the problem. on the drive shaft rubber bushing it has some cracks around it and one of the bolt is missing . they say that missing bolt can cause it to be unbalanced and will cause vibrations, so from what they explained to me it makes sense. i'm gonna try to find a bolt that is the same size and thread to see if it'll fix the problem. i'll update again once i put on the new bolt.

Edit: btw where can i find this particular bolt?

 

You'll need to purchase a Lexus nut and bolt. IIRC, the original one's on the vehicle are around 71 grams in weight. A bolt and nut isn't cheap, I think they list for around $23 each. They also sell bolts that range in weight from around 63 to 76 grams to assist in correcting vibration problems.

There are hash marks on the heads of the bolts that will tell you (the Lexus dealer) what the weight of the bolts in there are. One bolt has no hash marks. I can't remember what the weight of that one is, but don't be surprised if there aren't hash marks, just relay that information to your parts source.