Well it's about time for a fluid change and my ZF is at 380k without a rebuild and I was just wondering if there were any opinions on a slightly different fluid spec considering the mileage/wear. I've been running the Royal Purple ATF and "If it ain't broke don't fix it" but I thought I'd ask anyway. 3rd gear clunks a little when engaging but hasn't worsened over the last 80k. Tried some straight 30 weight non-detergent some years back and that was a wrong move--way too stiff shifting.