How Hot?

[S6PNJ]

How hot should a standard diff get in normal road use? I'm having issues with my speedo sensor/circuit and I think the sensor might be getting too hot and then cutting out. Reading a number of other threads (of which I couldn't find that many) do I check the diff oil by undoing the nut on the side (no, not me silly!) and ensure the oil is level with the bottom of the hole? I'm guessing I can't put ATF220 in there either if I find it low. I think the oil is Mobil SHC80W-140 ID, whatever that may be. My diff was very hot to touch (hotter than my exhaust pipes before the final silencer) but then there is a lot of metal to keep the heat as opposed to the (relatively) thin exhaust pipes.

Failing all the above, and the diff turns out to be not getting too hot, anyone got any other suggestions? (apart for the 'change the sensor' suggestion at £100 per pop!)

[S6PNJ]

Well I've adjusted the speedo transducer gap (again) this time to around 0.3mm and everything seems fine. I think the hot diff is a red herring as after a bit of spirited driving in between posts, everything seems fine. I dunno where the 'official' gap of 2mm comes from for speedo transducers, but when mine was set to 2mm I didn't get anything on the speedo. Ref the 'hot' diff, any lump of metal with oil sloshing around is going to get hot I guess, so I've no worries there!