Ok guys,

I have a 96 Z71 and the speedo and tach quit working... when this happened the transmission also quit shifting. Replaced speed sensor and connector, no fixie... I can clear the computer and the tranny will shift up thru drive and then hang in 2nd again... and the speedo and tach still don't work... any ideas?:confused:

Take out the headlight switch and make sure all connections are secure and there are no burnt wires. I know this sounds crazy but I had a bagged 95 silverado that wouldn't shift and there were some burnt wires behind the headlight switch. I rewired it and put a new switch in, tranny shifted fine after. I wish I had a technical reason, but I don't know why it worked.

Sounds like your ign switch failed. Super common on the 95to 99 trucks. Replaced literally hundreds of them for the same reasons.

Well, that is if your trans went into limp mode, which it should have.

ok... but what are the odds of the ign switch being bad on just the leads to the tranny and tach? i'm not saying that it cant happen, just that it doesn't seem likely... however, i will check the wiring off of the ign switch under the dash... any more ideas???????:(

I don't have the diagrams here to look at, but I will say that it's quite possible for one set of contacts that feeds a specific group of components to fail while the others work. Hell, I've replaced them for just this reason. But...I don't want to condemn the ignition switch just because I've seen it happen before (lumpdog is right though...TONS of those have required replacement). The first thing to do when diagnosing something like this is the check your powers and grounds which is going to REQUIRE that you get diagrams from somewhere. Vatozone might have them online. I wouldn't be surprised if your truck had "U" codes for network failure if you were to scan it. Have you hooked a scan tool up to see if the PCM is seeing a VSS signal?

Are you sure it is hanging in 2nd gear? That doesn't make a whole lot of sense. Limp mode on that tranny is 3rd gear and full line pressure since EPC goes away.

could definitely be in 3rd... not really up on the GM products since i'm a pretty faithful Toyota man... it's my sister's truck and i'm tryin to save her a little $ on it... the tach started working again(but for how long, who knows) but it's already loaded on the trailer to head to the nearest chevy dealer to get a full diagnostic in the morning... i'm hoping that it's gonna be something simple like the ignition switch/harness or the shift solenoids but we'll see... i'll post when i get an answer and thanks for the help

I just did this to my truck the other day, the reason why the tranny goes into limp-in mode is because its not seeing the 12v from the ign. switch, replace it and all should be fine.

The loss of power to the cluster and trans is the most common problem I have seen for the ign switch failure. Usually stopping, shutting the rig off on restarting it will cycle to ignition switch to make contact again. 95 was the first year that GM went to a new independent circuit setup in the trucks. They have had problems with ignition switches in the trucks ever since. Did a newer trailblazer for some of the same symptoms recently.

well shave my balls and call me stupid!!!:laughing: i'll be damned if it wasn't the ignition switch! appreciate the help and input from the masses... and sorry to doubt..:shaking: still a bitch to change!:flipoff2:

The loss of power to the cluster and trans is the most common problem I have seen for the ign switch failure. Usually stopping, shutting the rig off on restarting it will cycle to ignition switch to make contact again. 95 was the first year that GM went to a new independent circuit setup in the trucks. They have had problems with ignition switches in the trucks ever since. Did a newer trailblazer for some of the same symptoms recently.

Have you noticed it on the 99+ trucks as well? I haven't had to do one which might just be good fortune or maybe they aren't as bad. I haven't had to do one on a GMT360 platform like the Trailblazer either.