1989 1500 speedo wont work

I started out by changing the pickup at the rear of the trans. that was not it . then a garage told me it was the inst. cluster. I tried 2 used ones and they didnt work either . Any ideas?

I started out by changing the pickup at the rear of the trans. that was not it . then a garage told me it was the inst. cluster. I tried 2 used ones and they didnt work either . Any ideas?

You need to get it on a good scanner and see if the pcm has a MPH reading or signal in it.
If so it is in the cluster end if not it is the speed sensor end.
MT

The speedometer has a motor with a small gear driving a larger plastic gear which turns the numbers in the instrument cluster. In these trucks these parts can get dusty or dry. A little lube on friction points can solve this. Also the plastic gear driven by the motor can crack and slip on the shaft. A small amount of J-B weld fixes this.(make sure you clean it good if you lubed it).Hope this helps.