speedo jumping all over

[thesmokin12v]

i have a 96 cummins an the speedo is jumping all over even when stopped at a light the speedo will jump to a speed then back to zero when it does this the truck wants to start in second gear so i have to turn it off once turned back on it will be fine till the speedo starts acting up again it seems once im rolling bout fifty or faster its fine any one have any ideas

 

[zthatzmanz28]

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