As posted earlier, my car 05 S/C has developed a vibration at low speeds (generally when pulling away from a dead stop at sub 10 mph) as well as when going up hills at c.15mph - albeit only when cold.

Another thread suggests driving the car at a steady 55-56mph and waiting for the TC to lock up - vibration at that speed being characteristic of a broken TC - but my car is completely smooth...

Is there any other surefire way to diagnose? Thanks all

Could be sticking caliper which is freeing off once rolling? John
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That is a great idea - will check

Unlikely to be the torque converter lock-up clutch, I would have thought. It doesn’t engage until after the 2-3 upshift.



Phil

Thanks Phil - so torque converter judder would start at 24mph and go on for about 2.5 seconds as it engages?

Basically, yes (at light throttle). Additionally, you can see from the graph that in 4th gear the LUC is operating in its ‘controlled slip’ mode where it continuously slips at around 3% to absorb torsional vibration. Again, this could be a possible source of vibration if the LUC friction plate was worn. Only in 5th & 6th gears is the LUC fully engaged.

If you watch your rev counter needle carefully you should be able to see the LUC being engaged, when the rise in engine revs doesn't match the vehicle acceleration. If the vibration/noise that you feel/hear coincides with this then it’s likely to be the torque converter at fault. However, your issue sounds to be at too low a speed for this to be the cause.

Phil