Symptoms & Guide Overview:
This guide centres around problems with the automatic transmission not shifting to higher gears when the car is cold, as it warms up (usually after around 15 minutes) normal shifting occurs. It will take you through the removal and replacement process but be warned it's not a job to be taken lightly and will require a good selection of tools as well as reasonable mechanical skills. You will need access from above and below so ideally the task should be undertaken on ramps.

Cause & Replacement Process:
Three solenoids control up and down shifts and these are N88, N89 and N92. In most cases the cause is down to an ageing N92 solenoid although N88 and N89 have been known to cause similar problems and given the amount of effort required to replace one it only makes sense to replace these as a trio.

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So getting right into it, the location of the three solenoids is on the valve body and this is accessible by removing the front cover from the transmission however first we need to gain some access. Since all of the below should be fairly obvious it's in list form:

• Remove the battery
• Remove the battery surrounding plastics
• Disconnect the wiring harnesses behind the battery location and then unbolt the battery tray and remove
• Unbolt the fusebox and move it to one side

Next I highly recommend draining the coolant, it's JUST possible to remove the body cover with the coolant pipe in place but the time taken to work around it and then to figure out which way to wiggle it out will outweigh that benefit quickly! Pop the C clip from the passenger side inlet hose and then separate it to drain. In the middle of the back of the fan assembly is a 3 shaped bracket which holds the pipe in position remove this to allow the coolant pipe to be moved. If you have a 90/115 diesel then once drained disconnect the intercooler pipe and get that out of the way as well.

If you have a twin fan setup then I would take the extra 5 minutes to unbolt (three star bolts) the passenger side fan as again this aids access significantly.

Next unscrew and withdraw the transmission wiring connector, then remove the earth strap from the engine and unbolt its securing bracket to allow the wiring harness to be move our of the way.

Finally we need to remove the selector sensor.

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Undo the bolt holding the shift cable bracket to the top of the shaft and remove, then mark the position of the three bolts arrowed above, disconnect wiring plug 2 and remove the sensor.

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You should now be in a position where you can see (and have moderately good) access to the 10mm retaining bolts that hold the valve cover in place. Pick a corner and work around they are all removed. The factory seal the cover onto the body using a silicone style sealant so the cover will still be well held at this point use a suitable flat blade to work around the cover and lever it off the body being careful not to disform it. Note that some oil will be behind the cover so have a catch tray handy!

Now if you removed that coolant pipe from earlier then the cover will just drop out below, if you didn't then you need to attempt to slide it up and left before rotating it. Note there is a breather pipe on the back of the cover (top left) which will need to clear about an inch before it can be dropped.

With the cover removed we now get our first glimpse of the pesky solenoids!

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Handily the wiring connectors are all colour coded so we can now disconnect the wiring plugs to N88 N89 and N92. They have a pip to depress and then will pop off the solenoid. The image below shows the location of the 3 we are replacing note we don't need to touch the lighter brown solenoid in the middle:

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Next we just unbolt N88 and N92 for direct replacement. N89 is a little different though - this little bugger has a nut holding it in place instead of a bolt BUT its on a floating thread which means its possible to loose the thread back into the valve body if you aren't careful!. Taking extra care whilst removing it and refitting it I didn't have any issue however I did find a handy youtube guide that someone made who has obviously experienced this problem first hand!




It's now a case of rebuilding it all. I would highly recommend replacing the oil at this point if you haven't done recently so you know you have a serviced autobox. >> Link <<

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Once rebuilt I set about testing the old ones to see what the issue was, I noticed all 3 engage as expected but N98 stuck and took some time before it released which was the cause of the problem. I would speculate that more frequent changes of oil may have helped stop this issue from happening as I noticed a reasonable amount of particulate in the oil.