I am going to attempt to do my first ATF D/F. Help me with some questions.
1. Do I have to do the D/F on a level ground or can I do it with the van on the ramp?
2. How long after the van is turned off should I do it? Does the fluid need time to drain back in the sump?
3. What crush washer should I buy for replacement ? Is it an 18mm washer or a 20mm washer?
I will do 3 D/F in the span of 3 weeks, it hasn't had a ATF D/F yet. It's at 42K miles.
1. It should be level when checking the fluid level after re-filling. But for draining, it does not matter much. If you look to see where the drain plug is, and orient your car so it is sloping toward that, a little more will come out. I park angled in a slightly sloping driveway to achieve this. So I'd recommend to do this if it is easy, and not worry about it if it is not. No jacking or ramps needed, although many find it more convenient to jack/ramp it.
2. You want the fluid hot so it flows easily - it will stay hot for a long time. But you also want any particles to be up and suspended in the fluid so they drain out, rather than having settled to some local minimum. So I try to drain quickly after I stop driving it.
3. I just buy the Honda ones, so I don't know 18 vs 20mm. But I do know that I don't actually use them, even though I've got them. I just re-use the one that's on there and have never had a problem. Why? Convenience, reducing waste, on-going science experiment to see if it ever leaks with this method.
(4) The idea of separating multiple D/F's is good, if you do need to do multiple. I never have. 42k miles is pretty low. Back in the second millennium when Honda used to publish an actual maintenance schedule rather than program a computer that would adapt based on how much $$ you've still got in your wallet, the spec for the '99 Odyssey was: first change (single D/F) at 45k miles, then every 30k miles after that. The first interval is higher since ALL the fluid is new at the beginning of that interval. However, that spec was written before they realized how fragile those AT's were. I currently do single D/F's at 10k mile intervals on my '99 and '11.