Jsut come back from a trip on the motorway and here is what happens:
On ordinary roads on the way to the motorway, i.e. below 60 mph and 2500 rpm, the overdrive seems to work, although sometimes it refuses to engage and sometimes it engages but then the whole car shakes badly. I come on to the motorway in overdrive and then, when I accelerate to about 70 mph, the overdrive just disengages, but I cannot feel anything, not the usual jerk when it comes on and off. Doing 70-75 mph at 3500-4000 rpm. Come off the motorway, down a dual carriage way, nothing, then back onto the motorway again (throughout, I keep pressing the overdrive button when I want it on, and if nothing happens I leave it on, the light works fine) and then after a mile or so on the motorway, the whole car goes bang and the overdrive is back. It stays engages the whole way, and when I come off, it disengages when I change gear down, I then go 2-3-4 and press overdrive button but nothing and it refuses to come on again the whole way back home.

George
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'87 745 GLE Turbo Diesel Intercooler (D24TIC/M46) '88 745 Turbo Intercooler (B230ET/M46)