www.jec.org.uk

The ZF 4HP22 automatic gearbox was used in the 3.6 XJ-S and the XJ40. It’s a good box but as with anything mechanical it will still give problems eventually. A common fault is that especially when cold, it becomes reluctant to change up from 1st gear leaving you crawling along with a screaming engine. Eventually it changes up and will operate normally until the next cold start.



The problem is caused by a sticking governor located in the rear of the gearbox, this article is intended to give an insight on how to fix it. I don’t know your mechanical ability so I’m reluctant to give a step by step guide. This will, however, supplement your service manual and I hope also it will give you the confidence to have a go. What other choices are there? well, you can have a professional gearbox overhaul (very expensive), get another box from the scrappy (which will be just as worn out as the one you have now and is a pig to change) or sell the car (you wont get much though if the gearbox doesn’t work!).

Before we get started, I’m assuming you have previously replaced the gearbox fluid (Dexron II), filter and its ‘O’ ring. This is always the starting point for any auto gearbox fault and cures many problems. What did you find when you were in there? Furry black magnets, dark opaque fluid, a black film covering anything made of steel? Good and expected. Shards of metal, lumps of plastic? Bad, go out and buy a new gearbox! That black film I mentioned is the same stuff that is making the governor stick, all we need to do is clean it off and job done!

You will need a 30mm socket and a 27Torx bit. You may need some ‘O’ rings and seals, you quite likely won’t though. The job can be done with the gearbox in the car, ideally with the car on a lift but quite easily if SAFELY positioned on four axle stands at the jacking points raised high enough for you to work underneath. Enough said about safety, its your head under there, use it or lose it!

You don’t need to drain the fluid or remove the pan. Using a scissor or bottle jack with a wood support, take the weight off the gearbox, remove the four bolts holding the transmission support, bearing in mind its quite heavy and still under spring pressure, lower it to the floor.
Remove the heat shields, one above the exhaust, the other under the propshaft.
With the gear selector in Neutral, turn the flange at the rear of the gearbox to enable the four bolts and nyloc nuts to be removed, swing the propshaft down and to the side to give enough room to work.
Lower the jack supporting the gearbox enough to make work easier while still giving support.
Prise the steel lock washer off the output flange nut, turning the flange as necessary.
Put the gear selector in Park, undo the 30mm nut (anticlockwise). It may be tight if you’re unlucky, if so you may need to use extra leverage or an impact driver. With the nut off, the flange will simply pull off.
It should now look like the photo below:



You will have already noticed if the output seal was leaking, if so you can replace it later.
Place your Mum’s washing up bowel underneath to catch any fluid and remove all the bolts holding the rear extension in place, there is one bolt longer then the others, but its obvious where it belongs, there is also a bolt hiding between two of the ribs, all are get-attable with a normal ¼” socket set.
There are two locating pins so the housing won’t fall off, carefully pull it rearwards to clear the output shaft without damaging the oil seal, place the housing aside.
The photo below shows what we now have:



The governor is behind, and attached to the wheel which along with the pawl makes up the parking lock, I bet you always wondered how that worked!
Place the gear selector in Neutral to disengage the pawl and carefully pull the wheel/governor off the splined shaft.
The photo below shows the three governor sealing rings.



On very early gearboxes these rings were metal, if yours are, replace them with later rubber ones. If yours are rubber inspect them, they are a fairly loose fit but should have good sharp edges, if they are they should be fine to re-use. There is also an ‘O’ ring on the output shaft, again, it should be ok to re use it as long as its not compressed or damaged.
Clean the entire housing carefully with lint-free cloth. The pawl is easily removed to be cleaned, just make sure it goes back the right way and that the spring is correctly located.

By now you will be fed up of laying under the car, so take the governor to a nice clean workbench, it will look like the picture below:



It all strips down easily, just be methodical about where all the parts go and don’t allow the spring loaded parts to fly over the neighbours fence. The governor will show witness marks from the three sealing rings, that’s fine but run a finger nail across to make sure there are no grooves or damage, Replacement governors are available, but are hellishly expensive.
Clean all the parts using white spirit and the wife’s toothbrush and dry carefully using lint free cloth, use an air line to blow through all the passages, nooks and crannies.



You probably noticed a light black film on various parts, that is all that is needed to stop the thing working. Were not talking lumps of gunk here, its all very delicate like and quite surprising that it could have caused you so much grief.

Assemble the governor, lubricating all the parts in clean Dexron II fluid.
If you needed to replace the oil seal in the rear housing, it is only a push fit and very easy to change. If the thin paper gasket came off without tearing it’s quite likely that it will re-seal again.
Everything goes back together in reverse order, obviously cleanliness is paramount but you knew that anyway. Top up the gearbox fluid with new fluid, about the same amount that drained out. Check the level properly the next time it’s up to correct temperature in the normal way.
All done then! Take it for a test run. Doesn’t it work nicely! – you owe me a beer.

Parts list:
Governor sealing rings JLM892
Output shaft oil seal JLM686
Housing gasket JLM698

Just a note on the transmission mount, have a good look at the foam buffer and spring seat rubbers, they are a common failure and this is a good time to replace them. There is a procedure in the Haynes XJ40 manual on how to replace them but don’t believe them, its wrong. Don’t worry though, I will explain all in another article soon.

PS
Remember to dispose of your mum’s washing up bowel and wife’s toothbrush and deny any knowledge of their existence.
Pop

Very interesting! I have a '94 6 litre V12 with the late 4-speed box. It also occassionally sticks in a low gear, usually second, and then has to be driven screaming along. However, this is normally after a while, not when cold like with your model's box. It also has a very snatchy change now.

My local main dealer suspected the wiring loom to the top of the 'box, so they stripped the exhaust system and goodness knows whatelse to get at it and check it, but it was found to be OK. Their proposal now is to replace the transmission ecu but it's 500 pounds, so they recommend that I borrow one from an identical car, so it can be seen if this cures the problem, before splashing out on a new one. Unfortunately I can't find an identical car.

Have you any idea if my model's 'box also suffers from a sticking governor?

Thanks for any advice at all you might be able to give.

Welcome to the forum.
I think you will have the GM 4L80-E, a different beast altogether. I'm not that familiar with them but I don't think it has a governor, all gearshifts being electronically controlled. The Transmission Control Module should store fault codes which can be read by the Jaguar Diagnostic System. I would have thought the wiring was a prime suspect, especially the connections at the multiplugs and sensors.
If you have the workshop manual CDROM you maybe able to work through the symptoms. Sorry I can't be more helpful,
Link to CDROM
Pop

Very nice write up Pop, looking forward to the gear box rear mount episode.
I know the Haynes manual is incorrect. I did once find a website with a good write up on the mount, together with photo's, but I cannot find it now

I did once find a website with a good write up on the mount, together with photo's, but I cannot find it now
Hi Nigel, thanks for the kind words, The gearbox mount website was likely mine as well on my old mph150 website, although its now exists only on Jag Lovers and the Nine Lives CDROM.
I will get around to putting it here for reference soon!, Cheers,
Pop

The gearbox mount website was likely mine as well on my old mph150 website

Thats the one Pop, are the pictures still on the JL site??

I've posted it under a new heading, photos are a bit crinkly, but if anything needs explaining let me know!
Pop

Nine years on from my original post...

Recently I had noticed that especially on decending hills where I have put the gear lever in position 3 to assist engine braking, the box would hunt up and down, as if it coudn't decide what gear to be in.

I knew the fluid and filter was ok, see other threads, so thoughts once again turned to the mechanical governor. No harm in having a look and cleaning it.

One thing I hadn't factored in is that I am nine years older, the job would be fiddly but not that technical with a four post lift, but on the floor on axle stands I seriously struggled. A couple of hours a day was as much as my back, neck, eyes and muscles could stand.

At the time of writing, it is all back in place although of course some minor problems have been noted. The main battery cable runs along the transmission tunnel, supported by plastic clips. Two of these have lost their rivets resulting in the clips rubbing the prop shaft. To replace them means having the prop shaft out which I decided I can't do lying on my back, there is is no fear of the cable dropping or rubbing the prop shaft at the moment so I removed the loose clips and will monitor the situation, if more clips fail, it will have to be booked into a garage to be done.

The heat shields over the exhaust are held in by self tapping screws, some of these had lost their bite and were spinning and loose. Larger diameter replacement screws have done the job for now but if they come loose again a more permanent engineeing solution will have to be found.

A very quick inspection shows that the rear brake lines, brake pads and discs are ok, and there are no leaks anywhere. Tomorrow I will grease all the nipples on the rear suspension, clean everything up a bit, (including the remains of the Badger mentioned elsewhere), and finish.

I did notice that the rear nearside wheel has some movement top and bottom that the other side doesn't have, wheel bearing? I will have to have a closer look.

Ramblings finished for now, more rubbish to follow no doubt.

Al,

I`m sure PTJS 1 would join me in offering you a honorary membership to our newly formed Crippled Jaguar Maintenance Engineers Welfare Society. You have sufficient physical issues and points score to allow us to include you on "The List". All we ask in return is a couple of pints of decent ale when we next all meet up to cover Society administration costs. We are all heart.

Nice repairs. Keep it up and be thankful you don`t have a supercharger to remove!

Mike.

Pop,

It's ironic isn't it - as the bodies of our XJSs become valuable as they get older, our own bodies proportionally are getting worth less and less!

I hope you're able to get to the bottom of the gearbox hunting problem, plus the other little problems that you've found. I'm sure you'd do this anyway, but one thing you should consider before dropping that prop again to fix the battery cable clips, is to mark the prop and gearbox flanges to make sure that it goes back in the same alignment. Prop imbalance is an annoying thing and if yours is fine now, keeping the same alignment to the gearbox can only be a good thing.

As an aside, one other thing that has also changed in the 9 years is to consider running Dexron III rather than the original Dexron II in that box. I started a fluid and filter change a few weeks ago (will write up when finished) and have done 4 drains and refills so far, as I can only get 2.5 litres out per drain. So I'm using some old containers of Dexron II to do this flushing and will then do four fills of Dexron III once the filter is changed.

Take care under there!

Cheers

Paul

Lying on my back on cold concrete for a couple of days resulted in me having the worst cold/man flu I've experienced in a while. I'm up and about now but having passed it on to the wife I am in trouble once more!

The car however seems to have responded well to its surgical procedure, a good run out in it today showed none of the hunting problems so far. It was sluggish in engaging gear a couple of times likely due to losing about a litre of fluid. It's a problem I've had before, it needs filling more then the max level to cure. Off to the shops this week.

Mike, Yes I will hapily join the 'Crippled Jaguar Maintenance Engineers Welfare Society'. I also expect we were all early members of the 'Lets take our toys apart on Boxing Day to see how they work club'

Al