DA51

I have spent the last week reading every thread on the Internet concerning the "Thumping" in the trunk area on Lexus' vehicles and I am still looking for an answer. I have 162,000 miles on my 1992 SC400. I've owned it for 16 yrs. I have the Factory Shop Manuals. I've been replacing "Wear Parts" since 2001.
2010, I replaced every control arm, tie rod ends, sway bar links and sway bar bushings in the front. I replaced the Transmission mount.
2014, I put on my 2nd set of HP Blue Tokico's, new sway bar links and lubed the sway bar bushings trying to quiet the "Thump". This month I replaced the rear 2 lower control arms on each side and new sway bar bushings. The "Thumping" is still happening. I have new rear upper control arms , but have not installed them. I will need to lower the subframe for clearance. Quite a bit of work for an old man. I don't want to be killed or have a heart attack trying.
I used a Rubber Mallet and pounded on my rear Strut bars/bushings and they are tight.
I wonder if my stock 25 yr old springs are shot? Are the new Tokico's not working? Are the 4 subframe bushings shot? Are the 2 Differential bushings shot?

Those that have solved the riddle, Please respond.
Thanks.

t2d2

iTrader: (8)

I would guess it's something that happens while driving and is tough to replicate in the driveway, like the mufflers bouncing on their hangers or the sway bar end links shifting under load. Solution: Turn up the music and hope nothing falls off.

DA51

I took the mufflers off to do the rear suspension and have not replaced them. I like the sound. New sway bar links.
I'm leaning to the Diff bushings. With the new stiff shocks and now new lower control arm bushings the weak points in the carriage is magnified. I need to have someone drive the car and I ride in the trunk.

DA51

I found my Thump in the Trunk over bumps. The left strut mount has broken. It allows the shock/nut to float up/down. I compared it to the right side which is not broken. I used a large washer and sucked up the shock and no more thumping noise. A least it will be easy to remove with my new bolts in my control arms.
Ordered parts from Rockauto.

DA51

The rear strut mounts are broken inside. The metal sleeve had separated from the encased rubber and shock rod was floating-bouncing on top and bottom.
I used Monroe strut mounts. They are a little larger diameter and will not hold the bump stop in place. I drilled 2 holes and used screws to capture it.
I would suggest replacing these every 100k mi.
I replaced the passenger side strut mount and found my Tokico shocks leaking, now I have to wait another week for parts

DA51

A tip on broken Strut Mounts. The mounts have a flat on one side of the hole for the shock rod. When you torque the Shock nut, if the nut spins and does not tighten and the rod is spinning that tells you the strut sleeve has broken free of the rubber inside.
Mine were broken in 2012 because the rod was spinning.

DA51

HP Tokico Shocks are on Back order at www.autoanything.com until Dec 2016. I did find a pair for the back on EBay (their last set).
I wonder why these shocks are not kept in stock by Tokico?

flash9

I have been getting a clunking sound over uneven payment when driving around 25 to 35 mph.
I recently installed new suspension and as part of it, I used new shock top mounts. I really hope my rear passenger side shock top mount has not already failed.
It was recommended to me that it might be the rear sway bar, so, my first step will be to separate the sway bar end links from the rear suspension to see if the clunking sound goes away. If so, than I will replace the end links and sway bar bushings.
If not, then I will look closer at the shock top mounts.

1A1

Great job.Thanks for posting up this information.

Steve K.

t2d2

iTrader: (8)

I wonder if that's the case on both of my rears? They look just like your broken one, which makes it tough to tell if it's by design (Tokico Illuminas) or if both are simply shot.

1A1

Those Tokicos have the adjusters up top so the are going to be taller. They look fine to me.


Steve

t2d2

iTrader: (8)

Above the nut is taller with the adjusters, but the part below the nut has the same sunken appearance as DA51's broken strut mounts in posts #4-5. Hopefully you're right, but I've got enough clunking going on back there, it seems likely that the mounts are bad. I haven't been under the car yet to look for blown sway bar end links and the like, though.

t2d2

iTrader: (8)

Can anyone else weigh in on this? I looked at other rear strut mounts, and they all have that sunken setup like both of mine, and like DA51's "broken" one. Examples:

http://www.rockauto.com/en/catalog/l...rut+mount,7600

I also checked my '94 with good/new rear suspension and it's the same way.

Here's another recent post of relevance:

https://www.clublexus.com/forums/sus...ml#post9679550

I assume the "small metal seat" is the sunken portion? If DA51's metal seat was broken, and adding the big washer at the top replicated its function, then what about the non-broken one that isn't sunken? That seems to be the source of our/my confusion.

Blkexcoupe

iTrader: (8)

I had to pull out my stock suspension to look at this. My setup is sunken too, so I'm not sure what is going on. My initial impression would have been that his passenger side mount was broken.

The "small metal seat" is machined on to the shock. It prevents the shock from going completely through the top hat.


It's kind of hard to see, but there is a groove that the washer sits on, and the washer is basically the "small metal seat". If the top hat is bolted all the way down it the top hat sits directly on that washer. If it isn't bolted down all the way the shock theads will move up and down creating a clunking noise.

DA51's setup was broken, so his center nut was bolted down properly to the top hat seat, but the seat (recessed portion of the top hat) broke away from the rest of the top hat, so he fixed that by adding the washer and nut on the top to prevent it from moving up and down. It's basically sandwiching the broken portion. The original seat keeps it from going all the way through, and the new washer prevents it from dropping down.

t2d2

iTrader: (8)

^ That makes more sense, thanks for illustrating it. The recessed portion of the top hat and the metal seat of the shock assembly... I got confused thinking they were referring to the same thing.