Just bought a 2008 2500HD W/ LMM 6.6 Duramax. Planning on flushing the trans with transynd and also doing the power steering. Redline lists ATF D4 as a suitable replacement. I realize GM has two newer spec power steering fluids. I would prefer to go synthetic as this system is under a lot of stress. Any issue going with an ATF like Redline D4 or just stick to PSF? I prefer Redline but this is my first diesel. DMax folks chime in on this please. Thanks!