J_D 2.0
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- 2009 VE SSV M6 on LPG and 2022 Kawasaki Z650L
Well the recommendation is mostly because the transmission may be relying on that extra friction to not slip if it’s old and you don’t really want to find out your up for an immediate rebuild 5 seconds after you take it in for a “harmless flush”.I like The Car Care Nut and enjoy his videos and his advice but I’m still sceptical about the notion that one shouldn’t flush an older auto as the floating clutch particles are providing grip that the clutches need to grab the gears (while not blocking the fine oil passages and solenoids within the box itself?).
If such was true, given all the businesses selling snake oil remedies within our parts stores, you’d expect to find a transmission fluid additive containing finely ground clutch material for added grip I’ve seen transmission additives that claim to reduce slip. I suspect such is achieved by softening the seals which helps those one way ball values and solenoids work better and this provide the designed pressure to the clutches (none claim any form of clutch material is contained within specifically to aid clutch grip)
In my view a full flush is the way forward and if an auto then slips with the correct fluid level within, because all the clutch material has worn out and was dumped with the old fluid, the trans is already stuffed and you should be considering a rebuild
Sure the transmission is almost certainly on the out anyway but the flush forces it to immediately show its hand and for you to immediately go all in on a transmission rebuild you probably weren’t planning on!
The far safer option is to replace a portion of the fluid through the pan drop and if/when you start getting transmission slip you might have a few months before it craps out entirely to get the money together and book in the trans rebuild, or replace the car entirely.