1996 strange speedometer issues

[TexasRebel]

So I have posted a thread similar to this 2 years ago and never got a response of any kind and still have the issue.

The truck is a 1996 Sierra C1500 4.3 with a 4l60e.

The only time my speedometer is accurate at a dead stop. As soon as I start moving, the speedometer climbs quickly and bounces at the same time. By the time I'm doing about 55mph, it shows me doing somewhere around 80 and when I'm going around 35, it shows something around 65 or 70. I have to use my phone as a speedometer and it's quite annoying.

 

[moondog1]

Have you thought about swapping the whole speedo cluster? I had a couple repaired in a couple of ford's and it was much easier to just swap the whole cluster.

 

[AK49BWL]

Is the transmission shifting normally, and at the speeds you'd expect it to shift? If not, VSS on the transmission is suspect. Otherwise, cluster electronics... You can tear into it and simply replace the electromagneto... Possibility the control board is bad tho, and you can replace that by itself as well. Make sure you get one from a 4.3 equipped truck like yours tho or your tach will be stupid next lol.. Or go extreme and replace the whole cluster. Same thing tho, from a 4.3 truck only.

 

[Erin]

So I have posted a thread similar to this 2 years ago and never got a response of any kind and still have the issue.

The truck is a 1996 Sierra C1500 4.3 with a 4l60e.

The only time my speedometer is accurate at a dead stop. As soon as I start moving, the speedometer climbs quickly and bounces at the same time. By the time I'm doing about 55mph, it shows me doing somewhere around 80 and when I'm going around 35, it shows something around 65 or 70. I have to use my phone as a speedometer and it's quite annoying.

My uncle just had his cluster sent to a company in Washington who checks the cluster & makes any repairs needed. Cost him $189. His speed was off also, but says it’s perfect now. Sorry, I don’t remember the company name.

 

[Erin]

I believe it’s iss automotive.