Posting this to help others.
2006 IS350 (RWD), ~160k miles. This story starts out 100% stock/oem.
The steering is loose, feels sloppy. Results in lane wondering. Most noticeable on rutted or rough roads. Feels like and old Ford Bronco with the loosely machined steering box. At first I thought it was bump steer (struts) or control arm bushings. Been swapping parts to narrow it down. Here is a brief history and feed back for each upgrade along the journey.

First upgrade was lower control arm bushing (+alignment), swapped stock for RR-Racing bushings. Nice feel improvement, less "slop" & greatly reduced steering deflection under hard braking (particularly when traveling down hill with hard braking). This reduced a majority of the lane wondering, but something was still sloppy.
Second was Megan Racing Sway bars (front & rear) along with strut tower braces (front & rear). Turn-in and steering feedback while cornering improved. Had planned to do this unrelated to the steering slop.
Third try, Tire swap + alignment. Have never been a fan of Yokohama tires. Suspected they were blistering or de-laminating. Acquired the car with Michelin tires on rear & Yokohama on front. When it was time to replace tires, went with matching Michelin, all season, stock size. Ride feel and steering + grip improved drastically. Still a small amount of loose slop in the steering feel. This time only noticeable above 50mph oh the highway when lane changing, or in the canyons making S turns in the switch backs. Windy side gusts will also remind you its there.
Then I find it. Another contributor. The universal join in the steering column. Located between the steering wheel and the brake pedal (inside the cabin not the engine bay). As I sit in the car, engine on (steering unlocked), in park. Wiggle the steering wheel left and right until there is resistance. I found almost an inch of sloppy steering wiggle followed by a faint "thunk thunk thunk" sound that kept in time with the wiggle. I have yet to swap the part. Attached videos of universal joint in steering column with sound. I would like to swap to the ISF steering ECU, but want this problem resolved first. Hope I do not need to swap the entire steering rack and this u-joint replacement will solve the issue.


view: under steering wheel

 

The 2012 or newer isf steering ecu plus the steering wheel damper inlay insert is worth the investment. Especially if you’ve done some critical suspension mods like you have.


i dont know for sure the solution to your issue. However, if it were me, I would be looking into replacing the front lower left and right ball joints. I would go with moog, trw or Mevotech. Also I would replace the inner and outer tie rods for the left and right side as well since these can all be replaced in one go.

did you replace your sway bar end links? If no, I would look into spending the extra money and get the figs engineering sway bar end links for both the front and the rear bars, as well as the figs superpro poly sway bar bushings. Just be sure to match the diameter bar thickness with the appropriate bushing size and all should fit perfectly. I use them even though I’m using cusco front and rear sway bars.

as for more stability at highway speeds, I would also look into sourcing a lexus f-sport 5 point rear under brace, or the ULTRARACING equivalent and comparable brace. Lastly I would definitely recommend looking into the ULTRARACING steering rack braces, there’s two of them and both do make the steering feel, much more razor sharp and responsive. I have them both.

Do you have any shock / spring mods? Or are they stock? Stock shocks imho (springs too) rather suck when talking about driving over 70mph and feeling stable/planted. Before the suspension mods I would be scared to death to drive over 75mph. Now, due to not having a correct alignment, I’m now scared to death driving over 100mph. However I know with a realignment from some suspension guru (if I can find one), I know it’ll feel planted to 120+mph.
The last piece of the puzzle are tires. Michelin pilot sport 4’s are imo the best for summer tires. Bridgestone pole positions are a close second, except they weigh a ton. Yokohama advan tires are nice, same with their suv tires. But the other categories I am not too fond of. Hankook venture are decent but they feel like crap even though in reality they actually do perform almost as well as the Michelins. I would stay away from nitto. Bf Goodrich are pretty good too, except they are beyond loud, despite the usual very good pricing. Not familiar with perilli or continental/Goodyear or falken or kumho tires so I can’t say.

 

OP - lift the cars nose so you can access the pinch bolt on the shaft at the rack. If it can be turned in place where it is with ratchet, tie the steering wheel to the brake pedal so it can't turn freely.
Unbolt the couplers, if it can be removed, pull it but you might have to unbolt the R&P.

Tying the wheel in place will save the clock spring from being damaged.

How many miles on this?

GL

 

Oh, one last thing, the rear toe angle can drastically impact a cars steering inputs specifically over bumps and changes in tire grip. If tire wear allows it, advocate for toe-in condition over zero-toe and do not accept a toe-out condition.

I know I won't win a popular vote here but performance parts with open exposed spherical heim joints are not intended for DD. Road debris, moisture, salt and no means to keep them lubricated without a boot in place makes them a bad choice for DD. I would recommend OEM components over these unless your monthly dream is to grease them and replace them every year.

JM2C

 

Was concerned about 100% compatibility with the steering ECU swap. Wanted to avoid loss of features or compatibility issues. Have not looked into the details yet. The damper insert seems simple. Wonder if mine being 2006 would have fitment issues for mounting hardware. Didn't Lexus release the damper insert after the '06 year?

Think tie rods and ball joints are contributing to some slop? When making an "S-Turn" the moment between left to right turns, there is a hang time followed by a non-audible "thunk" weight shift that can be felt through the steering wheel. Also can be felt when going 45mph+ on a straight, but bumpy country roads. As if the wheels are leaning from side to side or the steering rack is loose. Not sure how else to describe it.

Sway bar end links were replaced when sway bar was swapped. Went with OEM style, non-adjustable. Should I swap for something better like you recommended Figs? Still on stock ride height + stock shocks, though I did want to swap the shocks in the future and do a bushing kit to refresh the suspension. The product page for 'Figs 2IS sway links' states "Designed for lowered vehicles only. Max length is shorter than factory links"

Looked into the f-spot 5 point subframe brace a while ago, but found it discontinued and was not sure where to proceed from there. I did find the UltraRacing counterpart. Good it hear its a recommended brand. Thought you loose the under skirt if installing chassis braces? Any increase in highway noise as a result? Should I just dive in, do all the braces or are only some worth it? (Front Subframe Tie 2pnt, Front Steering Rack 2pnt, Rear Subframe 6pnt, Rear Subframe Lateral 4pnt)

~160k miles nearly all stock/oem parts besides my listed upgrades. If you want the dirty details... water pump, alternator, and front windshield have been swapped. There is a small bit of pulley whine, though it could be the alternator (previous owner chose non-oem).
Thanks for the alignment tips!

 

The rack has some slop due to a slotted bushing, and the rubber doesn't make full contact with the bore. It's a pain to upgrade AWD and even more painful for the RWD model. As far as the "tunk" does the OEM sway bar have the collars still intact next to the bushings?

https://www.clublexus.com/forums/sus...-bushings.html

 

Would the UltraRacing Front Steering Rack Brace (SKU: UR-LA2-170) reduce some steering slop? (Not sure if links to parts are allowed other wise I would provide it. Compromised by listing part SKU.) I see what you mean about the slotted bushing in the steering rack, UltraRacing brace might make no difference. Wonder if swapping to aftermarket bushing would be an option, or if that would make the steering feedback overly harsh. Interesting engineering choice from the manufacturer.
OEM swaybar was swapped for Megan Racing sway bars (front & rear) with new oem style end links. I think the loose u-joint in the steering column might be the thunk. It certainly contributes to some of the steering slop. Previous poster recommended ball joints and tie rods. Starting to feel like they are a good recommendation.

 

Hello did you manage to solve this issue? My car has the same steering wheel play in the center.

 

I have both the ultra racing steering rack braces. Yes it helps a lot with the slop.


For freeway stability I highly recommend the under brace (5 or 6 point brace). Also recommend figs center underbody tunnel brace.

i also recommend the isf steering ecu even despite your current condition. It will help make it even easier to identify your steering dissatisfactions.

 

Each part I swapped helped reduce the issue, but is still present. Have not yet swapped the steering column u-joint. I believe this is the main culprit in my case.
When are you experiencing the steering play? All the time? Have you checked your alignment? Do not accept toe out alignment - neutral or toe in only. Did you swap the lower control arm bushings (LCAB) for a stiffer version (Figs/RR-Racing)? This helped with some bump steer and steering deflection under hard breaking. Particularly when breaking hard while going down hill, increasing weight transfer to the front and exaggerating the control arm bushing flex.
With the car parked, can you wiggle the steering wheel side to side freely with either a tactile or audible "thunk" before feeling turning resistance? My wheel wiggles freely about 0.5in side to side. Think of the old Ford Broncos with the loosely machined steering box, but not quite as bad. This is because of my bad steering shaft u-join

I currently have a list of items to refresh the steering & suspension. Suspension is still original OEM everything with almost 175k miles (excluding sway bars and LCAB)
-The List-
steering shaft u-join
suspension bushing kit, OEM spec (unless someone recommends an alternative)
steering rack bushings, OEM spec
steering rack brace (ultra racing)
struts/coilovers
under chassis braces (ultra racing: front subframe + rear subframes (6point & 4point))
tunnel brace (figs)

If none of these improvements fixes the steering and suspension dynamics, I will admit defeat and replace the whole steering rack and wheel hub assemblies.
Though life is busy right now and I have no spare time to wrench beyond the obligatory maintenance. These are future plans.



Good to hear! Thank you for the feed back on the steering rack brace. I had not heard of the tunnel brace, but it does make sense. Consider it added to the list! I find two of them on the Figs website. There is a standard brace and an offset brace. When would the offset brace be needed?
I have installed and calibrated the ISF steering ecu. Good mod, would recommend! Went with 89650-53041. Big improvements with feel when pushing through the canyons and sport mode actually changes the steering instead of just the throttle when compared to the stock '06 steering ecu.
Also picked up the steering damper 45713-53020 and some pedals but have not installed them yet. I find myself enabling sport mode around 65mph to stiffen the steering and act as a damper to compensate for the loose steering (temporary solution).

 

Yes, the steering wheel damper is easy to install yourself. Just need a screw driver I believe and maybe a pry tool.


the figs under tunnel chassis brace, I got the regular version because it was cheaper and I have the oem mid pipe. The offset version is just incase you have a custom exhaust setup that places the cats or resonator in the spot of the oem braces spot. It’s just to accommodate after market midpipe setups.

i believe you just need a 14 or 15mm socket to install the brace with the new bolts that come with it.


in the very near future (after Memorial Day), I believe I will start on my project for this old dog Lexus. I may document it, not sure but yes I believe I will be putting in a nice new suspension (again) and finally swap out the motor. As for the steering slop, if there is anything due to the u joint then I most definitely will change it out. I’ll keep my eyes peeled for it.

The difficulty for me now is finding a shop that is competent and honest and is willing to do the tasks at hand… easier said than done that’s for sure.

 

From the steering wheel to the rack there should be absolutely zero play in any of the joints. If any play is found, replace intermediate shaft and/or joint in tilt column. The steering column has the angle sensor, the rack the assist. Any loss in angle detection/feedback is going to make an I'll driving car. Braces, LCAB, and/or lowering is not going to fix this type of issue.

Source - former alignment tech

 

Did you ever install the intermediate shaft? Having the same sloppy feeling in my steering and trying to narrow it down as well.