GLA Gearbox Slippage and Transfer Case Concerns

Slipping and rough shifts definitely suggest something amiss with the transfer case. You mentioned oil leakage – have you checked the transfer fluid level? Low fluid, even without significant leakage, can cause those symptoms. Gear grinding noises would further point to gear wear. Have you noticed any unusual sounds? Also, "mechanical wear" is pretty broad. Are you able to isolate the source of the wear?

Thanks for the prompt response. The fluid level was indeed low, which I've since topped off. The grinding noise is intermittent, primarily when shifting under load, and seems to be emanating from the transfer case area. By mechanical wear, I'm referring to the degradation of the gear surfaces themselves – pitting, scoring, that sort of thing. I'm trying to ascertain if this is a common failure mode for the GLA's transfer case before I pull it apart. Could prolonged operation with low transfer fluid accelerate gear wear significantly?

Operating with low transfer fluid will absolutely accelerate gear wear; the fluid's designed to lubricate and dissipate heat. Given the grinding noise and confirmed fluid loss, it's highly suggestive of internal damage. While I can't definitively say it's a 'common' failure without statistical data, the symptoms align with defective gears. You could attempt a fluid flush and refill, but if the damage is already done, it might only provide temporary relief. I would strongly advise taking it to a qualified workshop for a proper diagnosis.

Understood. I appreciate the confirmation. Based on your assessment and the symptoms, I'll proceed with a professional diagnosis at a workshop. It seems likely that a transfer case overhaul or replacement is inevitable. The eventual repair cost was 330€. Thanks again for your insights.