1995 BMW 325i Manumatic problems

[Brii]

I have a 1995 BMW 325i. It's a manumatic.

When driving manual, first and second gear work fine and have normal rpm ranges. The problem when in third gear (starting at about 60km), even driving at 90-100km it revs at 5 and 51/2, with red line being at 6. Even if I bump it up, into Drive, it doesn't change. I don't understand why it is revving so high.

I'm assuming like most vehicles, it has three gears, with D being overdrive. Is it possible that the electrical is wrong, or that overdrive has been disabled??