Transmission -- no filter, just screen?

Why do some transmissions have a filter made of fiberous material while others have just a fine metal mesh screen?

Why aren't fiberous filters sold as replacements for metal screen filters?

Reply to
larry moe 'n curly
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Barring a catastrophic failure of some sort, there really isn't a source for a lot of harmful contamination inside an automatic transmission. The main wear product is a very fine "dust" from the lined clutch plates and the bands. Its not big enough to clog the valves in the valve body, and having it carried back into the clutch packs doesn't do any harm since its the same material that they're made of anyway. The planetary gears are in constant mesh, so they don't ever shed chips to the same degree that gears and synchros in a manual transmission can. And finally, the tolerances of the valves in the valve body are known, so a wire mesh that will trap the biggest particle that could potentially jam a valve is all that is really needed.

That said, some manufacturers did always prefer a finer filter to trap some of the clutch dust. It can potentially wear things like bushings and thrust washers, but not very badly. And it depends on the materials chosen for bushings,, bearings, and thrust washers, too.

And probably the best way to improve overall trans fluid filtration is to do what some companies (Chrysler comes to mind) did for fleet applications many years ago: take the fine filter OUT of the pan, put a mesh screen there, and then put a full-flow replaceable cartridge type filter (like an engine oil filter) in-line with the cooling lines. that allows a fluid and filter change without dropping the pan, and the wire mesh filter will catch any stray large chips that do form for whatever reason.

Reply to
Steve

| Why do some transmissions have a filter made of fiberous material while | others have just a fine metal mesh screen? design flaw,

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para 12

1 can fit a filter ( e.g. Mazda 323's petrol filter ) onto the joint ( betw metal pipe & rubber hose ) of a-t-f's cooling ( return ) pipe ( cooler than exit pipe ).
Reply to
TE Chea

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