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Senior Member
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Join Date: Dec 2014
Location: Utah
Posts: 4,976
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Senior Member
Join Date: Dec 2014
Location: Utah
Posts: 4,976
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FWIW - they will not add KDSS. KDSS models have a different frame. I don't know what the differences are - I'd guess they are very minor, but the frame part number is different and likely has some different mounting bolt locations or something along those lines. Also it would be cheaper to simply replace it with a KDSS model than install KDSS on an existing one.
I have KDSS and have had some steering vibrations with unbalanced tires like this issue. I actually currently have a bit of vibration right in that speed range. However, generally I have not had a problem with it and I assume it's due to my tires wearing out and being in need of a re-balance.
The fix that is used on the Lexus GX models per a Lexus TSB is to switch the spring in the steering rack to reduce feedback. This is something that I had an issue with in a 3rd gen 4Runner that has a very similar design and the same steering shimmy issue at times. On those you could just get underneath and actually adjust the spring preload in the steering rack yourself. It was pretty easy to do. On the 5th gen the adjustment mechanism is very hard to access. Unfortunately they should have fixed it when they swapped steering racks.
The real issue is somewhat unknown. It's a complex system and it obviously has a resonating frequency issue at that speed. Something as simple as a different density of rubber bushings on the control arms or even a different alignment setting often resolves it. I don't think anyone really knows exactly what the cause is or what a true solution really is. I suspect that all suspensions exhibit this to some degree, but most would not exhibit the issue until speeds higher than normal use
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