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Just when I thought I had this issue nailed.......
In short, I have had this issue of the speedo and/or the centre diff light flashing happen three times between 150,000 to 200,000kms. This time, I thought I would look at it myself rather than spend another several hundred dollars at a mechanic. This explanation is quite detailed, but I will cover the whole process, so hopefully some others can see where they fit into it.
The speedo failed again, so I took out the sensor in the extension housing at the back of the transfer case. Once again, smashed from the inside. What I have learned, is that it is now emerging as a common problem with Pajeros as they get a bit older, that the tone wheel inside the extension housing becomes a little loose. The tone wheel sort of looks like a coffee cup with lots of evenly spaced holes around the sides. It sends a magnetic pulse to two sensors which are for the speedo, cruise control and the centre diff light. The tone wheel rattles around a bit and smashes up the sensors.
The best thing at this stage is to drain the oil from the extension housing. Have a close look at the magnet on the drain plug. A little bit of very fine filings on the magnet is normal. If there is chunks of metal about the size of a pea or similar, you have a serious problem and a failed speedo or flashing diff centre light is only the symptom, not the cause. This is rare, but is the issue I was faced with and I will cover this further down.
Assuming there is nothing nasty on the drain plug, your problem is most likely a loose tone wheel.
Taking off the extension housing where the tail shaft goes into is fairly straight forward. Take out the tail shaft by undoing the bolts where it attaches to the diff. You don't need to touch the bolts at the front end of the tail shaft. Slide the tail shaft forwards (to the front of the car) slightly, then it will drop down and you can slide it out of the extension housing. About a couple of cupfuls of oil will come out of the end of the extension housing, so be ready to capture this. Undo the bolts that secure the extension housing and pry it apart; a silicone gasket is holding it in place.
If your problem is a loose tone wheel, the fix is to GENTLY peen the tone wheel with a centre punch on the inner shaft where it slides over the main output shaft. To do this, take the tone wheel off, and slide it over a broom stick handle (or similar) which is firmly mounted in a vice. Just a LIGHT tap through each aperture in the tone wheel. Remember, you are only trying to take up about 0.5mm or so, just so it fits snugly over the main shaft.
When you are replacing the damaged sensors, put a thin washer under where the securing bolt goes. This has the effect of creating a little more distance between the sensor and the tone wheel, so if the tone wheel moves around again it is less likely to hit the sensor. This extra bit of distance will not affect the ability of the sensor to get a proper reading from the wheel. Hopefully for you, this will be the end of your problems with flashing diff lights or failed speedos.
OK, now is where things can get nasty and expensive if you noticed foreign material inside the extension housing. As I mentioned above, I have learned that this is rare; no mechanic or 4wd place I spoke to had seen this before, and from trawling this website I have only found one other case, but it happened to me. So, have a close inspection inside the extension housing for any foreign bits of metal. If you noticed excessive metal on the drain plug for the transfer case, then some of this may well have travelled into the extension housing through the oil channel. Inside the transfer case there is a set of planetary gears. In my case these gears disintegrated and fragments of metal had travelled into the extension housing through the oil chanel and smashed up everything.
Removing the transfer case is a major project unless you have a comprehensively equipped workshop. My recommendation is don't do it yourself; now is the time to make it a cheque book project. If you are stupid, stubborn and determined to do it, as I was, this is how to do it.
At this stage you have already removed the rear drive shaft, so next undo the rear cross member, AFTER you have suitably supported the transmission underneath with a trolley jack, or similar. Gently lower the engine/transmission assembly so you have access to everything. Remove the front drive shaft which connects the transfer case to the front wheels; you may have to disconnect the joint in the exhaust to wiggle it around. Disconnect all the electrical cables for the wiring.
Remove the bolts securing the transfer case to the transmission. There are a few particularly nasty bolts on top of the transfer case. The ONLY way to undo these is with a rattle gun; there is simply not enough space to turn a spanner or socket.
The transfer case weighs about 55kgs, so be ready for this weight. I found the best technique was to use a thick piece of chipboard about 500mm square and bolt that onto a trolley jack. On most trolley jacks you can remove the lifting cup so you can bolt the chipboard down securely. I used two trolley jacks and one assistant. By carefully adjusting each of the trolley jacks under the transfer case to alter the height and angle, you can get it out, and back in again later.
I was told by a couple of reliable sources and also through this website that repairing a transfer case is prohibitively expensive. Given that they rarely fail, it is fairly easy to get a good one from a wrecker. Mine cost about $900.00 including buying new oil.
Installing it all is the same process in reverse, then have a couple of well earned beers, plus some for your assistant.
Let me know how you go with your particular problem. Cheers
In short, I have had this issue of the speedo and/or the centre diff light flashing happen three times between 150,000 to 200,000kms. This time, I thought I would look at it myself rather than spend another several hundred dollars at a mechanic. This explanation is quite detailed, but I will cover the whole process, so hopefully some others can see where they fit into it.
The speedo failed again, so I took out the sensor in the extension housing at the back of the transfer case. Once again, smashed from the inside. What I have learned, is that it is now emerging as a common problem with Pajeros as they get a bit older, that the tone wheel inside the extension housing becomes a little loose. The tone wheel sort of looks like a coffee cup with lots of evenly spaced holes around the sides. It sends a magnetic pulse to two sensors which are for the speedo, cruise control and the centre diff light. The tone wheel rattles around a bit and smashes up the sensors.
The best thing at this stage is to drain the oil from the extension housing. Have a close look at the magnet on the drain plug. A little bit of very fine filings on the magnet is normal. If there is chunks of metal about the size of a pea or similar, you have a serious problem and a failed speedo or flashing diff centre light is only the symptom, not the cause. This is rare, but is the issue I was faced with and I will cover this further down.
Assuming there is nothing nasty on the drain plug, your problem is most likely a loose tone wheel.
Taking off the extension housing where the tail shaft goes into is fairly straight forward. Take out the tail shaft by undoing the bolts where it attaches to the diff. You don't need to touch the bolts at the front end of the tail shaft. Slide the tail shaft forwards (to the front of the car) slightly, then it will drop down and you can slide it out of the extension housing. About a couple of cupfuls of oil will come out of the end of the extension housing, so be ready to capture this. Undo the bolts that secure the extension housing and pry it apart; a silicone gasket is holding it in place.
If your problem is a loose tone wheel, the fix is to GENTLY peen the tone wheel with a centre punch on the inner shaft where it slides over the main output shaft. To do this, take the tone wheel off, and slide it over a broom stick handle (or similar) which is firmly mounted in a vice. Just a LIGHT tap through each aperture in the tone wheel. Remember, you are only trying to take up about 0.5mm or so, just so it fits snugly over the main shaft.
When you are replacing the damaged sensors, put a thin washer under where the securing bolt goes. This has the effect of creating a little more distance between the sensor and the tone wheel, so if the tone wheel moves around again it is less likely to hit the sensor. This extra bit of distance will not affect the ability of the sensor to get a proper reading from the wheel. Hopefully for you, this will be the end of your problems with flashing diff lights or failed speedos.
OK, now is where things can get nasty and expensive if you noticed foreign material inside the extension housing. As I mentioned above, I have learned that this is rare; no mechanic or 4wd place I spoke to had seen this before, and from trawling this website I have only found one other case, but it happened to me. So, have a close inspection inside the extension housing for any foreign bits of metal. If you noticed excessive metal on the drain plug for the transfer case, then some of this may well have travelled into the extension housing through the oil channel. Inside the transfer case there is a set of planetary gears. In my case these gears disintegrated and fragments of metal had travelled into the extension housing through the oil chanel and smashed up everything.
Removing the transfer case is a major project unless you have a comprehensively equipped workshop. My recommendation is don't do it yourself; now is the time to make it a cheque book project. If you are stupid, stubborn and determined to do it, as I was, this is how to do it.
At this stage you have already removed the rear drive shaft, so next undo the rear cross member, AFTER you have suitably supported the transmission underneath with a trolley jack, or similar. Gently lower the engine/transmission assembly so you have access to everything. Remove the front drive shaft which connects the transfer case to the front wheels; you may have to disconnect the joint in the exhaust to wiggle it around. Disconnect all the electrical cables for the wiring.
Remove the bolts securing the transfer case to the transmission. There are a few particularly nasty bolts on top of the transfer case. The ONLY way to undo these is with a rattle gun; there is simply not enough space to turn a spanner or socket.
The transfer case weighs about 55kgs, so be ready for this weight. I found the best technique was to use a thick piece of chipboard about 500mm square and bolt that onto a trolley jack. On most trolley jacks you can remove the lifting cup so you can bolt the chipboard down securely. I used two trolley jacks and one assistant. By carefully adjusting each of the trolley jacks under the transfer case to alter the height and angle, you can get it out, and back in again later.
I was told by a couple of reliable sources and also through this website that repairing a transfer case is prohibitively expensive. Given that they rarely fail, it is fairly easy to get a good one from a wrecker. Mine cost about $900.00 including buying new oil.
Installing it all is the same process in reverse, then have a couple of well earned beers, plus some for your assistant.
Let me know how you go with your particular problem. Cheers
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