[b] [size=3][font=Arial Black][size=2]HELP! CAN ANY ONE GIVE ME ADVICE AS TO WHY MY 94 LS400 STARTS TO VIBRATE AT SPEEDS OVER 50? AS I DONT FEEL SAFE DRIVING MY CAR WITH MY FAMILY IN GOOD ADVICE WOULD BE WELCOME AS I AM GETTING A BIT WORRIED CHEERS

the front wheels need balancing

[quote name='nereus4951' post='411816' date='Jan 28 2007, 12:22 PM'] [b] [size=3][font=Arial Black][size=2]HELP! CAN ANY ONE GIVE ME ADVICE AS TO WHY MY 94 LS400 STARTS TO VIBRATE AT SPEEDS OVER 50? AS I DONT FEEL SAFE DRIVING MY CAR WITH MY FAMILY IN GOOD ADVICE WOULD BE WELCOME AS I AM GETTING A BIT WORRIED CHEERS[/quote]


Check for any clunking sounds during deceleration and while placing the car in REVERSE. This could be a sign that you have faulty u-joint(s).

There are several things that can cause the Lexus to vibrate at 50.

Firstly check that your tyres are correct pressure all round (i think it's an average of 33) then have your front wheels balanced that should cure it. If not that have the joints checked out like the man says.

Good luck

does it get worse when you are at wobble speed and push the brakes?

I have a woble over 70 and I'm convinced it's warped brake discs as it's more prominent when braking

I had the same problem this week. look at this post

[url="http://www.lexusownersclub.co.uk/forum/index.php?showtopic=39954"]Post[/url]

try driving a farely short distance, about 2-3 miles at 30-40mph and try not to use the brakes. then check wether one disc is considrably hotter than the others or that one wheel is very dark from the brake dust compared to the rest.

When you've done all the above, check that the rubber prop shaft doughnuts aren't split.

Ah!
Thanks for the info guys, I noticed a lot of brake dust on one wheel only after a trip to work and back (20 miles).

I have got new anti rol bar bushes to fit next week so I'll check out the discs/calipers then.

Well, I fitted 2 new discs and pads to the front.... and TADA! no change at all.

Think the prop shaft rubber is next on the list, maybe rear discs but it's becoming an expensive guessing game.

hi mate hope you sorted your problem

my ls400 does the same but over the spped of 70mph the whole steering vibrates
the problem front upper controls arm bushing or the ball joint of the arm.
you got two way of sorting it out

1:buy after market rubber and fit them in the upper control arm

2:if the ball joint got wear in it then you have to replace the whole arm.which is very expsive about £405 inc vat,

Hi Manni,

Did you fix your vibration then?
I just changes the anti roll bar bushes so I had a look at the upper control arms while the wheels and brakes were off, it all looked ok but not sure if there is an easy way of telling if the control arem are worn or not?
Same issue with the ball joint too, how do you tell if it's ok or warn enough to cause this issue?

It's an ongoing saga for a few folks so anything we can define is good to document.
Cheers.

Get the car in the air and ask a garage to check around the front suspension and lnks. They shouldn't charge you for this and may show you the problem.

The other thing is to jack the front wheels up in turn and try and wiggle the wheel holding your hands at 12 & 6 o'clock on it for movement.

Any movement and you've got a problem. Just keep wiggling until you can see where the movement is. Listern for noises when doing this aswell.

I know I'm reviving an old thread, but I've had a similar problem that I thought might help others.

My LS 400 was vibrating pretty badly between 60-70mph.

First thing I did was get the wheels balanced. This didn't stop it.

I then swapped the front and rear wheels around. Didn't fix the problem either.

I then removed all scum on the wheel face and regreased, in case the build up - yet small - was the problem with maybe the wheel centring.

Then I fitted new brakes (all round, rears were gone anyway) with the brake fitting kit, still no improvement. Though I did notice a ceased caliper, which was the cause of the problem. Since is was gone beyond repair, I had to get a second-hand one (Lexus wanted 600 quid for a new one!) and fitted it myself which stopped the problem right away. I did try and release the ceased pistons a few times and oil the baby up, but they would soon cease again.

What was happening, I assume, was that the caliper was in effect locking the pads onto the disc, so it was like driving around with one wheel almost trying to brake itself! And when it warmed up, on motorways, everything was expanding in the heat and pushing against each other, thus the vibration.

The caliper warped my new discs, which I also replaced, so all is good now. But warping is very easy on these Lexus beasts, there was an article on this forum somewhere I read where it told you how to brake properly (IE not sitting at the lights with your foot on the pedal, as it keeps the heat locked into the braking system, resulting in warping, for example).

Very good informative post thanks for sharing it with everyone.
Good point also regarding holding the car on the brakes in queues etc, OK for a short time but I tend to go into neutral then parking brake if it's going to be a while as it also takes the strain off the transmission.

[quote name='Seb Harvey' post='637914' date='Feb 16 2009, 03:08 PM']The caliper warped my new discs, which I also replaced, so all is good now. But warping is very easy on these Lexus beasts, there was an article on this forum somewhere I read where it told you how to brake properly (IE not sitting at the lights with your foot on the pedal, as it keeps the heat locked into the braking system, resulting in warping, for example).[/quote]

OK, sorry, but I'm going to have to debunk that one...

Firstly, it's [b][u]very[/u] rare[/b] that brake discs actually warp. They're pretty hefty lumps of cast iron, generally, and are not prone to changing shape. In brief, the MAIN cause of "warped brake disc syndrome" is an uneven layer of brake pad friction material leading to hotspots & metal composition changes. See [url="http://www.stoptech.com/tech_info/wp_warped_brakedisk.shtml"]this excellent website[/url] for the full monty.

Secondly, [b]normal[/b] usage (and that includes the occasional BIG stop) will not cause "warping"; so if you're just sat at the lights, and assuming you've not just executed a 100mph-to-0mph emergency stop, you'll do NO damage keeping your foot on the brake pedal.

[quote name='steve2006' post='637980' date='Feb 16 2009, 06:33 PM']but I tend to go into neutral then parking brake if it's going to be a while as it also takes the strain off the transmission.[/quote]

Another myth, I'm afraid (boy am I going to be popular today )... when your engine is idling, in gear, and your foot is on the brake, no part of the tranmission is moving [i]except[/i] for the "fluid flywheel" (i.e. the turbine portion, which is attached to the engine, and pushes the fluid around). There is a [b]very slight[/b] heat input into the fluid (because it's moving relative to the rest of the trans, which is stationary), but nothing the normal oil coolers can't deal with easily, even in extremely hot conditions.

I guess there is a very slight stress on the transmission side, where the fluid is attempting to turn it - but that stress is miniscule compared to the stress you put on the same part when you accelerate from the lights, or up a hill, or - indeed - anytime when you are accelerating...

In fact, I'd go as far as to say this: If you're constantly moving in & out of neutral/drive (or, worse, you go all the way to park), you'll actually cause MORE wear on your gearbox - on the selector mechanisms!


All of that said.... I will do the same thing (into N or P if there's a significant wait looming), but that's more to rest my braking leg than to save anything in the car...!

However, if you have just had new pads and discs fitted (at least for the first 500 to 1,000 or so miles), you might want to take your foot off the brake at traffic lights for long stops, especially when the brakes are very hot. This would be to prevent an imprint of pad material being transferred to the discs which could subsequently build up to form an uneven coating of pad material on the disc surface. This would result at some point in experiencing the effects of what people tend to refer to as "warped discs" but is in fact an even build up of pad material on the disc surface.