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ZF 4HP22 automatic transmission

It would appear that getting information about the 4HP22 is rather like getting blood from a stone. At best, it seems to be very much an old-boys' network, so I thought I'd put this page together to hold all the titbits of info I've gathered.

Links to other sites

Documents and info

Following is an intensely useful page that seems to change URLs regularly and occasionally disappear altogether, so I've mirrored it here. The following info is not mine - it was unashamedly torn from this other page. If you're the copyright owner of this stuff, let me know.

'A' clutch burnout - Teflon Seal replacement

I took a few pics of core tranny parts to give a strong idea on how to repair this common defect, this tranny is in m20 bimmers, m30 bimmers after about 84, volvo 740 without overdrive non turbo, Peugeot and jag don't know which. this is how to repair the main problem with the tranny, when the car will only move in reverse and in extreme cases not move at all.

This is the cause of the problem, these steel seals leak and send pressure to the 1st gear clutch pack and burn it up.
Teflon seal locations

These are the bolts to take out to remove the bell housing and pump as a unit, unless you need to replace the converter bushing you do not need to take the pump apart or off of the bell housing (I will describe the procedure for that and why at the end of the post).
Bellhousing bolt locations

Here's the bell housing / pump assembly off:
Bellhousing / pump assembly removed

Here's the front of the rest of the tranny and case:
Front of transmission open with pump removed

Grab the A-clutch basket and yank it out of the bellhousing / pump assembly:
Removing A-clutch basket

Here's the back side of the A-clutch basket, there's a steel bearing surface missing in this pic that you will have - between all rotating parts there's a bearing race (looks like a washer), flat roller bearing and another race:
Rear of A-clutch basket

You can leave the shaft in the A-clutch basket or pop it out so the basket will sit flat on a bench; or you can just leave the whole thing in the bellhousing / pump assembly while you do the clutches. There's a spring clip that holds the basket together that you remove with a screwdriver:
Spring clip on A-clutch basket

Inspect the basket for cracks, I've found a few blown up from people who didn't take no for an answer. Also inspect the groove the spring clip was in: those ears can snap off:
A-clutch basket inspection

Here's the pack of disks and plates - there's a black wavy disk on the top and bottom of the pack that you re-use:
A-clutch pack

This pressure plate is under all of the clutches, you can see some of the burnt clutch on it, clean that off and clean under it:
A-clutch pressure plate

Here's a new disc and steel - soak the discs in fresh ATF for a few minutes before installing:
New clutch plate and disc

With the teflon seals there should be a drill bit and a sandpaper flap drill thingie - I've never drilled the hole in the 25-30 trannys I've done, it's up to you. It is done to relieve any future leak pressure, I've been doing these for over 5 years and have yet to have one of my repairs fail. The sandpaper drill thingie is used to knock down any burrs left from the steel seals here:
Pump bore

Seals...
New teflon seals

...and where they go:
Teflon seal locations

After cleaning the bore by honing it, stick the input shaft back in the A-clutch basket (if you removed it) and lube the seals and bore with ATF. Make sure the three pieces of the bearing are in place and slide the A-clutch assembly back into the bellhousing / pump assembly. It will seat with a thunk and spin freely.

Put this bearing race on the of the input shaft/a-clutch assembly, then the bearing and last the other race, it will be the smallest of all the races:
Bearing assembly

Then insert this gear into the A-clutch assembly...
Gear

...until it's bottomed out in the clutch pack:
Gear in final location

If you didn't break the paper gasket that seals the pump to the tranny you can reuse it as a new one is a bitch to fit onto the pump without ripping it.

All that's left is to reinstall the bellhousing / pump assembly into the tranny - get comfy as this can be fun sometimes! The object is to slip the fingers on the back of the A-clutch into the slots of the 2nd gear clutches in the tranny case. Twisting the input shaft helps - you have to 'feel' your way in. There will be no gap between the pump and tranny case when seated. Tighten the 17mm bolts in a cross pattern, and you are done.

Take your time: look carefully at how everything came apart, and if in doubt dump ATF all over it if it's inside of the tranny! The Bentley manual has an exploded view of the tranny if I remember right.

When installing the torque converter, make sure it's all the way in: If the tranny and motor won't go together find out why, don't pull it together with the bolts as you can destroy the pump and converter.

I get most of my parts from these guys, but there's almost always a tranny parts place or two in town.
ATC Book

Converter oil seal

If the converter seal you just replaced is leaking again, the bushing behind the seal has walked forward and is blocking the drain: Time for a new bushing!
Bushing

It's hiding here:
Pump bushing

Take the bell housing pump assembly off as seen in the a-clutch repair and take the rest of the bolts out of it and separate the pump from the bell housing and take the bolts out of the back of the pump - you can thenstrip the pump all the way down and press the new bushing in. Reassembly is covered in the A-clutch repair.



This page was last updated: 8th January 2013 at 12:14pm GMT
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