E30 Zone

on my 318i after getting the diff welded i put it all back toegher and it worked fine until 5 minitues up the road the speedo stopped working, has the sensor with 2 wires goin into it on my diff got anything to do with it?
going past speed cameras with no speedo isnt fun.

the sensor in the diff is the speed sendor for the speedo. sounds like a loose connection seeing as you have just put it back together.

It could be corrosion in the diff sender plug and socket, but it's more likely to be an internal break in the wiring near the diff. Replace at least the last 300mm of the cable complete with plug - repairs won't last.

the sensor is badly corroded i jus put a tiny squirt of gasket sealer round it ;)
ill get a new one how much am i looking at?

I think switch cleaner would be more effective than gasket sealer. If the socket on the sensor is corroded beyond repair, put a wanted add on here. You should be able to get a good one for pennies, rather than the many pounds that BMW would want.

The senders themselves are plastic but the steel retaining plate for some reason corrodes like nothing else! If you pull the sender out, you can grab a new retaining plate and 'o' ring seal for about £2 from BMW.

If you've had the diff welded, there's always a chance the trigger wheel was a bent tooth which has then bitten a lump out of the sender