ZF & big balls

[Shackleton]

Thinking I'll tackle my flaring (2nd -> 3rd) ZF4HP22EH myself, anyone done one?

So far I've found reference to this service manual:

http://bmwe32.masscom.net/sean750/overview/OverviewServiceManuals_versie12.htm#ATSG

...and Boydie on here mentioned in another thread that he'd gotten a similar item issued by Volvo.

[Boydie]

Yes, I have a Volvo service manual but while its 99% common with the Land Rover unit the govenor is Volvo only, but beyond that the two are the same unit, the external casing is obviously different to match the Volvo chassis.

To strip one down you need a very clean area (bench) and ideally some special tools, not essential but they would be an advantage. Take LOTS of photos as you dis-assemble the gearbox, DONT rely on your memory of how the various components are located, especially the various ball bearings that act as check valves in the valve plate. Spend a couple of dollars (or ponds sterling in your case) and buy a small cleaning tank with a pump so that you can ensure that all the assemblies are spotless before you re-assemble, I picked one up for arround AUD$80.00 and have used it on numerous occassions since. A compressor with a blow gun is also a good investment to blow out all the gunge from the valve plate.

With the exception of the valve plate its just a pump, the valve plate is pressure controlled by the centrifugal govenor and opens and closes various ports to operate wet clutches which give you the various gears.

Replace the pump, it's the heart of the unit and is, in the ZF4HP22, very fragile, if I were you I would replace it with the larger and stronger ZF4HP24 unit but this will mean that the gearbox will be 15mm longer - this will involve a longer front propshaft and shorted rear but the weak link in the ZF4HP22 is the pump so give it some consideration, also I would advise that you replace the bevel gears. The gearbox mounts are easily ovalised to accomodate the longer gearbox. If you do use the ZF4HP24 pump you will need to make up two adaptors for the oil cooler as the connections are different, Ashcrofts can supply these to you at a reasonable cost.

If you are thinking of putting additional power into the box look at using ZF4HP24 clutches, get a set of second hand ones and see what installing them will involve, on some boxes a small amount of the casing needs to be ground out to accomodate the larger clutch plate assemblies.

Good luck and have patience.

[Shackleton]

Thanks Boydie. Even just the matter of fact tone is helpful, when so much of what you hear is that an auto box isn't for the DIY'er.

My box was badly neglected but has responded well to a handful of ATF changes (plus sump clean and new filter) over the 5k miles I've owned it. It flares shifting between 2 and 3 and that's really all I want to cure, otherwise it's very smooth. The whole point for me is to achieve that fix on a limited budget so an air compressor and a degreaser aren't on the cards. The only mod I'd like if money will allow is the torque converter upgrade.

So I'm thinking I don't need to mess with the valve body, if I understand the box correctly the pump and clutch packs form the front half of the box and I can limit my incursion to that area.

[duncmc]

I have found and booked marked this page for future reference should I ever need to do mine. http://www.cowdery.org.uk/zf.php

Its a Sherpa ZF4HP22 that is done, but its similar.

[Boydie]

The degreaser tank isnt a nessesity, an old baby bath, hot water and a few cans of aerosol degreaser will see you through this cleaning operation. The air compresssor isnt such and easy replacment, you really should service and check out the valve plate, if only to satisfy yourself that there isnt any crud from worn clutches in the journals, its not a horendous job, a quick trick is to use vaseline to hold the balls in place jouring re-assembly.

As for the torque converter look arround for a billet type rather than the welded and sealed-for-life unit, firstly they are stronger (I expect cries of rebuttal on this subject) and being machined from a solid billet of aircraft grade alloy they disipate heat far better and even better still they are fully servicable, some upmarket units are fully lockable.

BTW as far as your electronic control goes, you are on your own, I'm totally Ludite with electronics and others will need to assist you should you need help.

[Boydie]

Before you go too far, just pull apart the govenor, this can be removed from under the car after removal of the transfer box, my gut feeling is that this is where your problems are, remove it, clean it out and you may be very pleasantly suprised, generally ZF4HP22's do not like sitting arround for any length of time. My car was off the road for a month resulting me having to give it a total strip down.

[discomikey]

doesent RAVE cover the HP22? im sure my copy does, ill check tonight

[Shackleton]

Turns out it does... who knew, or who noticed (it was Mikey)

Found this HP22 thread that also has some info about modding an EH variant. http://forum.roadfly.com/threads/1709355-ZF4HP22EH-Transmision-help