Hey there all, when I bought my van (1986 cargo 2wd auto) the overdrive worked fine but it's been a few months since it's seen anything faster than 70kmh and I realised the OD wasn't kicking in.

The transmission works fine all round no issues at all but hitting the OD off button has no change in effect and the engine revs quite high trying to do anything more than 85kmh.

The OD light comes on and off with the button but because the transmission works fine in general I don't think it's a mechanical problem probably an electrical problem but I could be wrong.

Is there any common things I should be looking into that might cause the OD not to engage? It's probably good to mention the fluid is clean and filled to the right level.

Thanks!