Investigating failure of a ZF4 HP18 transmission. Part 3 скачать в хорошем качестве

Investigating failure of a ZF4 HP18 transmission. Part 3

Part 1    • Investigating failure of a ZF4 HP18 Transm...   Part 2    • Investigating failure of a ZF4 HP18 transm...   Part 4    • Investigating failure of a ZF4 HP18 transm...   Part 5    • Investigating failure of a ZF4HP18 transmi...   Inside an automatic gearbox pump:    • Inside an automatic gearbox pump   How the pump works:    • How an automatic transmission pump works   Part 3 of stripping down the ZF4 HP18 transmission to investigate why it failed. Please note - this isn't an in-depth 'how to' guide but more of a general interest into the innards of an automatic front wheel drive gearbox...and yes - they're every bit as complicated inside as you'd expect. The trick is to make notes, take photos, make more notes and then have a cup of tea before taking the plunge or get someone else to do it. Oh - and keep workplace surgically clean if you're rebuilding a 'box to be used again. Tiniest bit of dirt in the valve block will upset it. The story so far... Brake band has been disconnected and removed to enable the sub-assembly to be removed. While pulling related components, I spotted debris in the form of straw or dried grass inside! Severe contamination by foreign-object and since I never touched the 'box during my time (except when changing the ATF in a clean garage) the debris must have got in when valve block cover was off and/or a fluid change was carried out in a field. I reckon previous owner had changed the ATF and left it draining - probably outdoors in a strong breeze. No other reason or way of debris getting into the transmission unless of course it got in when refilling ATF through dipstick or the breather valve. Worth noting that when I bought the car, there was lots of dried grass, clippings and straw trapped between engine and undertray and the Ebay listing photos seemed to show the car on a recently mown field. Anyway, seems now that debris caused certain parts to jam up which in turn caused cascade failure and accelerated wear. Factor in that the previous owner had towed a caravan and the poor, hot running gearbox in a heavy car with shonky ATF changes could only lead to failure. Still - it was a cheap XM and we got two good years out of her. Here's a tip. If you are going to tow regularly for goodness sake don't keep to the standard fluid change intervals. You have to shorten the intervals between oil changes to compensate for the extra loads on the engine, transmission and running gear.