Re: 156 acuator what fails
It is mainly O ring type seals that fail in the Magneti Marelli actuator, which by the way is virtually the same unit as Ferrari, Lamborghini, Aston Martin, Fiat, forthcoming Lexus etc...
The BMW SMG unit is a licensed copy made by VDO Siemens.
Its a complex bit of kit that does wear out, and few people have bothered to look into the repair of them, which is a shame.
Eddie (mad) Mann of Alfaman at Rayners Lane Harrow has bit the bullet and will rebuild and test actuators, a fraction of the cost of a new one.
Where you are really stuffed though is Fiats gearbox casing which can crack at the selespeed mounting point, then you really do need a new gearbox, although its not as expensive as you might imagine.
You cant safely work on an actuator yourself though , as a diagnostic tool is required to de-pressurise it.