Mileometer failure on '89 Type 44 - Any BTDT?

[rob]

  Hi gang.

    My trusty 100 Av is beginning to show it's age this year, after many trouble free miles things are beginning to stack up.

   Latest failure is the mileometer/odometer last week. This model uses the electric sender unit on the final drive. The speedo needle works fine, but the numbers have just stopped going up! I wondered if anyone has and BTDT on the failure mode on this. - Am I heading right into the speedo unit or is there something else to try first?

  Thanks Rob.