When I had my 17 SS1LE Redline D4 also performed much better at the track too when things got hot. All around major improvements over stock! Shift quality did degrade overtime, the fluid runs very cool unless you are at the track so was my running theory, but a drain and fill fixs that up.
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On my GX460, Out Factory fill ATF that was dark as heck, even with a single drain and fill. Dropped the pan, clean the magnets and replaced the gasket and strainer.
In with WS, did a fluid exchange took some time but went smoothly 2qt out 2 in, till fresh fluid was coming out.
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