For some time now, my '89 E34 535i manual has had issues with jumping out of first gear when taking off. It happens most often when the car has recently been started, but not so much after it warms up. The clutch will actually engage, but the gear shift will jump out just as you start to move, sometimes quite violently. Not great when you are trying to pull out into oncoming traffic, or when taking off at the lights.

My mechanic checked the detent springs and said they are fine. He thinks there is an issue with the first gear "slider" (whatever that means - I do not know the inner workings of gearboxes that well). He thinks it would cost minimum AUD$1200 to repair and said most of the cost would be in parts and that is assuming that there is nothing else wrong once they open the box.

Anyone experienced this before? Is it a better option to get a second-hand or reconditioned box for half the price? (I could put it in myself). Anyone in Australia (Melbourne) know where the best place to find one might be?

Thanks!