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.
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