ZF 4HP22 auto gearbox question

Yes I think that will help. I believe you are right, you can also put a new filter in as the old one may be blocked with bits. Wash out the valve body well in petrol or thinners should do the job, just don't take any springs out as where they are sat and pressure can mess up the valving. If there are any bits in the fluid I'd positive flush it again (disconnect line to cooler, fit a pipe to it and put in bucket, get funnel ready for topping up, run engine, pump out all the atf, when it starts to run dry keep filling with 5l of cheap ATF (of correct grade) and the fresh stuf gets pumped out the system, when it runs dry again turn off, leave to settle, remove drain plug and let any remaining drain out).

Then fill with good quality fluid (redline, or synth) and I add an auto box pro additive from Wynns which also contains a seal conditioner to re-supple the rubber seals.

I think I have a filter on the shelf for a fiver + post if you haven't got one, =A312 retail I think.

Cheers, Greg.

I wouldn't be as worried as the last poster about disassembling the valve body and cleaning it out. It's no more complicated than a carburetor (if that word is unfamiliar to you, please excuse as I'm showing my age.).

The valve body is just a bunch of valves springs and check balls. Just be careful to get it all back together right. There are manuals for such disassembly and they do help. On my 1997 528, the most important thing was getting the two check valves that were placed between the valve body and housing in the right place. It scared me when I dropped the valve body and the two balls fell out. After staring at it for a while, it became obvious where to put them back. (Just pack them in grease so they stay in place until you get the valve body back in place.)

Best stuff to use is petroleum jelly - Vaseline - as it doesn't contain anything which might clash with the fluid.