Mate has an E28 520i with a ZF 4HP22, it's the normal version not the EH
with the electronic control and S/E/123 switch.

It was fine until he had the fluid changed, I'm guessing the change
loosened off all sort of old junk and it's ended up in the valve bodies.
It not jerks and changes gear when it feels like it. Car is no longer
safe to drive.

My question: If I drop the drain pan I think I can remove the control
unit and valve pack (if my memory is correct). Would I be able to clean
this out and do you think it would do any good?

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On 7 Feb, 23:36, John Burns <j... (AT) unixnerd (DOT) demon.co.uk> wrote:
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, £12 retail I think.

Cheers, Greg.

Greg wrote:
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.)

In article <45CD1BFA.2040904 (AT) verizon (DOT) net>,
Thomas Wright <rockystuff (AT) verizon (DOT) net> wrote:
Best stuff to use is petroleum jelly - Vaseline - as it doesn't contain
anything which might clash with the fluid.

--
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