Quote:
Originally Posted by bosstones
Sorry if this is thread jacking but it's somewhat related. I heard somewhere that, short of a full flush, a drain/fill (incl pan drop) only changes out 60-70% of the trans fluid . Thus a 2nd drain/fill is needed to get closer to a full swap (al beit still not at 100% but close enough).
Is that real or fake news? I never figured it was 100% for a single change but figured it was in the 80% (-ish) range. 60% would be pretty dismal but still worthwhile if it's never been touched at all.
Asking since Ive been meaning to do my trans fluid since I'm at 85k on the clock but was also going to do the sleeves, solenoids, etc... Ive got spare drain and fill plugs and fluid for a 2nd fluid change if needed but it wouldn't be worth doing the pan et all first should I do 2 fluid changes.
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The capacity for the BMW ZF8's is officially 8 liters. Unless you take the whole transmission out, you won't get more than ~5 liters to drain. Just refill what you got out and you should be fine. If you care about the math, 5/8 = ~63%. Do it twice, you get 86% out. Either way, don't forget to replace the pan or else you'll still have your old filter.
I changed my fluid twice, two weeks apart. Fluid was pretty dirty on first drain (93k!). On the second drain, it was noticeably less dirty, but still not fresh. The job is only takes an hour and isn't that expensive, so IMO probably worth to just do it twice, especially if you're getting up there in miles and it hasn't been done before.