Hello all After 20 years and 130000 miles my speedo and tach went out within a month of each other, datcon thanks. I am replacing with vdo gauges, anyway I can't remember the pulse count of the 50dn alternator in a 4106. I know there is at least one other gear ratio in 4905s or some of them. I had a 24 volt that had a different gear tooth count. If anybody knows the number I would appreciate it. Thanks olebusman