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SimonAllen

Bedford TM 4x4 8 ton cannot drive fault

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Hi,

Can anyone help on this? This ex-army Bedford TM has a gauge on the dashboard that shows two dials. They are both pressure gauges. The right one reads 7 bars and the left one 1.5 bars.  None of the gears will engage. To get the vehicle to move at all I have had to disconnect the servos and manually engage the gearbox underneath. Does anybody know what the correct reading for the air pressure on the auxiliary should be? My guess is that should also be around seven bars. Any idea why it is reading so low?

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East Sussex.  In Wheldon territory.  I had a chat with a guy who had one of these vehicles many years back.  I have a partial solution by mechanically pushing the gearbox into drive and disconnecting the air actuator. The air system is not working. I'm suspicious of the air supply. There is a combined gauge on the dashboard.  As I posted above they are very different readings and the one that I think works for gearchange is only reading 1 1/2 bars.  If you can throw any light on what the correct reading should be and why it is low, that would help.

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The auxiliary air pressure gauge is the lower one on the right hand side of the instrument panel, the nominal working pressure is between 7 & 8.4 bar, the warning buzzer should sound when the pressure drops below 5 bar.

It appears that you have an air leak somewhere.

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My mate who is away at the moment may be able to comment as he is ex-MOD vehicle mechanic.

Give me a week or so.

Regards

Larry

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Many thanks to all of you.  My brother and I had a session on the vehicle today.  I removed the gauge and swapped the two pipes.  The gauge is not faulty.  We ran the engine and were surprised to have the auxiliary air system coming in at 7 bars.  The other gauge is nearer to 8 bars.  The result is that the PTO and 2L and 4L work but 4H does not.  I think it is probably a stuck piston.  So we now have PTO and drive.  While we were underneath we drained the air tanks.  There are three.  One has two drains that needs a spanner to undo.  All the tanks had a lot of water in them which is not surprising.

What is odd though is that we have not done anything to directly fix the fault but we were seeing only about 1.5 bars or less on the auxiliary when the fault first occurred.  So if any of you can explain that it would help.

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By using it you are probably freeing it to move.

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