I have a 320i cdi (2004 model) which has done just over 100,000 miles. I noticed a shudder recently when driving uphill at low speed. The local Mercedes dealer diagnosed the problem to be a faulty torque converter. This was fitted yesterday for £1900. However on checking the gearbox oil sump they have found a lot of iron filings there which they say indicate that the gearbox is on its way out. They recommend fitting a new gearbox which will probably cost at least £4000. However they say I can drive it as it is and it may last for a long time. Any advice please?