speedo sticks at times

[elk_hunter]

hi all,

 

have a 99 Gmc Sierra with 4.8. This has happend since i got it used(didnt' notice this until I had it for about 4/5 months).

 

While driving on the highway over 60, at times the speedo doesn't move , yet i'm going faster, and the tach doesn't move. I only moves in about 2 1/5 miles motions. it will do this off and on for a few days, then will work fine for weeks.

 

And a few times i'll be at a stop light look now and my tac's at 2500 and mph is at 30. I take off and it usually drops down to 0 and then works fine.

 

Could this be a loose connection somewhere on the tranny or on the vss? The dash has never been removed, and the gauages are all orginal. I even remove the cluster and everything was connected and tight.

 

Thanks for the help!!!

[elk_hunter]

gues that everyone on here is as stumped as me, and others that i have talked to.