91 Ls400 vibrations

[Malc1]

Occasionally at 60 mph upwards .......  when it happens ......  not too often  🫢

Been overthinking this all these months .....  it's not tyres, nor pressures, nor anything to do with the wheels, brakes nor steering, mechanic says all that is just about " spot on " .  calipers too  ............... no lumps of stone in the treads either BUT  ....  might it be a slight, occasionally showing itself, imbalance in the propshaft ?

What is there that might cause this occasional undue vibration ......  and it can be quite unpleasantly severe too ........... could it be summat to do with the propshaft from time to time ?

I'm lost with it all ......  easily overcome when it happens, I just reduce to 50 - 60 mph !

Your thoughts please always welcome 

Thank you

Malc

[Razor61]

Rear engine/transmission mount maybe? Part# 12371-50010 and my advice is to just change it.

[Malc1]

3 minutes ago, Razor61 said:

Rear engine/transmission mount maybe?

Thank you .  I'll get him to peruse next time she's in for a little tlc  ....  heaven knows where I'd source any replacement tho !

Malc

[Malc1]

10 minutes ago, Razor61 said:

Rear engine/transmission mount maybe? Part# 12371-50010 and my advice is to just change it.

Thank you for the Part no. too 👍

Malc

[Razor61]

8 minutes ago, Malc1 said:

heaven knows where I'd source any replacement tho !

I think you know where you can get one………….Amayama or LPD or your local Lexus dealer.

[Malc1]

I remember when I bought my Mk3 from a member here about 13 years back he gave me a box of assorted bits and bobs …… I only ever used the plugs …… if there’s one in the box ( it will be hiding somewhere 🤔 ) might it be a common Part No do you know ?
Thanks

Malc 

[Razor61]

The one you need is a different part number to the 94-2000 LS400 so even if you have one for the MK3 it’s not the right one. Just buy the right one and have it fitted, they don’t cost ‘an arm an a leg’ and it’s probably goosed anyway.

[Razor61]

Just one other possibility for this - the front strut rod bushes. Apparently this can cause a vibration around 60/65mph.
Quote from a Buyers Guide on Club Lexus:
Strut rod bushings, every 100k miles. Symptoms are: clunk when you first tap the brakes (you'll hear it in parking lots), slight vibration when going 60-65 mph or a shimmy under light braking from highway speeds that will be felt in the steering wheel instead of in the pedal like warped rotors normally would.

https://www.clublexus.com/forums/ls-1st-and-2nd-gen-1990-2000/1019550-the-unofficial-ls400-buyer-and-owner-s-guide-2024-a.html

[Malc1]

Thank you ……. It’s definitely, but rarely,  at 70+’ish and vanishes to “ normality / zero vibrations “ when I drop her back to 50-65 or so 

No specific road conditions seem to affect this phenomenon either …….. 

Braking isn’t an issue …… when I’m in free-flow zipping past all those lumbering giants in those 7 seater monster passenger “ go faster “  truck SUVs 😂

We are so understated in our genteel Ls400s 😇

Malc