Speedometer and tach goofey

04 trailblazer 4.2 engine auto trans 4W 96K miles.
Tack pegged out towards botton without engine running and not moving engine running.
Speedometer stuck on 60 MPH sitting still.
But did drop down and start working after driving it.
Customer say it acts up on road and engineand transmission not running right
Good VSS/MPH reading and engine speed in computer.
Drove down road and outside of being a little sluggest does OK.

But Engine slow on response at 60 MPH and fast transmission
kick down when giving a little gas.

Thanks for any ideas.
MT

John, make sure the grounds on the l/s of the block are good, also the cluster gd under the l/s of the dash, 102 I believe in the wiring diagram. Then it may be the driver motors for both gages bad, which is was a common problem with these clusters, although this would not affect performance.

John, make sure the grounds on the l/s of the block are good, also the cluster gd under the l/s of the dash, 102 I believe in the wiring diagram. Then it may be the driver motors for both gages bad, which is was a common problem with these clusters, although this would not affect performance.

Maxwedge
Thanks for the input and info.
I was wondering about grounds.
I did find a tsb on a 06 about bad ground making speedometer act up.
I will try to find the ground points and check them out.
Thanks.

MT,

Goofy gauges are a known problem for the TB/Envoy and many other GM mid- and full-size vehicles around the 2003-5 years. The servo motors inside the gauge cluster are of poor design and need to be replaced with an updated design. There are a few ways to replace them: 1) buy them and install them yourself, 2) purchase a replacement service and send the cluster out for repair, or 3) go to the dealer to replace the cluster.

I opted for #2 about two years ago. Found a reputable sevice on eBay (yes, I know...reputable?). Cost me about $85 to have all the servos replaced, including shipping. Haven't had any issues since

Good luck with what you do, MT!

MT,

Goofy gauges are a known problem for the TB/Envoy and many other GM mid- and full-size vehicles around the 2003-5 years. The servo motors inside the gauge cluster are of poor design and need to be replaced with an updated design. There are a few ways to replace them: 1) buy them and install them yourself, 2) purchase a replacement service and send the cluster out for repair, or 3) go to the dealer to replace the cluster.

I opted for #2 about two years ago. Found a reputable sevice on eBay (yes, I know...reputable?). Cost me about $85 to have all the servos replaced, including shipping. Haven't had any issues since

Good luck with what you do, MT!

jdmccright

Thanks for the info.

Right now the customer is on hold driving it as is.

I was just looking threw a Dorman flyer 2010 Volume 2
Looks like they now have Fully Rean. complete instrument clusters for 02 Bravada and Envoy and 02-04 Trailblazer.
Have not checked price yet.
But.
Good Old Dorman to the rescue.

Problem is when replacing with a new cluster, the odo reading must be transferred to the new unit...probably not a big deal to you, but shadetree junkies like me would rather not mess with that. Good luck on that.

Problem is when replacing with a new cluster, the odo reading must be transferred to the new unit...probably not a big deal to you, but shadetree junkies like me would rather not mess with that. Good luck on that.

Thanks.
Yes it is a big pain for everybody.
Even the Old Car-Fax fox gets upset when mileage gets out of whack or jumps up or down to much.

The cluster maker or rebuilder can program in your actual mileage and keep the lisense office and state inspection department and every one happy.

In the good old days I would just sign a odemeter chage slip or flip the odmeter miles to where ever they needed set.