1850 Auto, incorrect speedo reading

[Richard the old one]

Many thanks Matt for the tip about sealing the splines as I have suffered from the problem. What I did to overcome the problem was to put some sealant between the drive flanges, prop shaft to rear axle.

[triumphtoledo]

Brilliant tip, thanks Matt

[trigger]

Apologies for jumping on this thread with my own similar question but i have the same issue but with a manual 1850, i believe the speedo cable is original and it's on the original 155x13 wheels but at a indicated 50mph I'm apparently doing 60mph according to the GPS on my phone, not ideal when in a average speed section of the A12 and you didn't realise... anyway should i be looking at this flange nut with a manual box or would a knackered cable be more likely? my speedo needle doesn't bounce like I'd expected with a worn cable. Thanks!