95 Tahoe Shift ind/Tach/Speed problem

Hey guys new here, I got a 95 Tahoe, 4x4, 5.7l automatic, power everything, 160,000 mi, and im having a problem. First saturday night my check gauge light came on, but all looked good, so i went home, it shut off after about a minute. Then i started it up sunday morning as always, no problems, made it around the block and the shift indicator light went out, my tach dropped and my speedometer dropped, figured i was just going up the street so id finish the trip and fix it there, but as i went to take off again, it was reluctant to begin moving, and once it did it wouldnt shift past first gear. Took it home, restarted it, same story. Disconnected battery, let it sit a day, hooked it back up, same thing!! im still paying on the thing and now i cant drive it, any, i mean ANY help would be so greatly appreciated!!! i followed all the fuses and the look good, couldnt find any vacuum lines leading to the tranny, found a black box sorta thing on the side though with two connectors filled with wires, is this some sort of shift sensor? could it be bad? Is there any vacuum modulator for the shift sensor? Im out of ideas and aamco ripped me off, i took it to them, they said it was fixed but no!! like i said it always starts, but 20 seconds later i lose indicator, tach, and speedometer. Thanks for the help. If i can save the estimated $150 diagnosis, and whatever repairs that come with it, id be ecstatic. I am somewhat car savvy so i can understand car terms as well.

P.S. Ive heard someon say this could be an ignition switch? Any ideas on that?

Could be the ignition switch, check voltage at trans fuse to see if it is the same as the battery, could check the transmission connector to see if a pin isn't backed out a bit- pin E should have 12v with the ignition switch on.

No power to the trans on pin E will produce your symptoms, your check engine codes may reveal the low power to trans and should give electrical faults for solenoids

Thanks jeremy, is pin E in the connector that connects to the black box on the drivers side? will it be labeled so i know which one it is?

Its in a 20 pin connector on the passenger side, the wire is pink. There is a picture of the connector end view here: http://www.jsm-net.demon.co.uk/trans/index_html_41b8510a.jpg

Thanks again jeremy. i tested "E" wire, and checked for cracks, breaks, exposed areas, and voltage was almost 14v while "on". Then checked fuse 20 (trans fuse) had exactly the same voltage. So i suppose that narrows it down to ignition switch huh? picking one up tonight, i have 30 days to return it so i guess if it doesnt work out, i can just take it back. I may have them run a diagnostic on it since i dont have the computer to di it with. if i find out anything i will post so anyone reading this, that has the same problems im having, can check for the same problems. If anyone else reads this and has any input, feel free to post.

Check the voltage at the trans fuse when it acts up, probably won't be 14v.

The circuit starts at the ignition switch, goes to the trans fuse, and then to pin E- some guages, and the speed sensor. If you are any good at wiring, there is a much cheaper alternative to a new ignition switch

Just for grins (:-), replace the #20 trans fuse. 80% of the time it doesn't help, but there's also that 20% hope that it will. Sometimes a fuse will look and test good, but with the amperage draw it may heat up and go open without showing signs of blowing.

As Jeremy-WI said, the power to that fuse comes from the Ign sw. It comes off of one of five contacts in the sw. The fuse is powered in the "off", "run" and "start" positions.

Ya the 80% odds were completely against me. Didnt work. However i did go buy a new ign switch, havent put it in yet so i can return it if i need to. Im bringing it into my work tomorrow, i dont have a garage at home so this way i can really dig into. Jeremy, when i tested the volts i WAS infact testing while the shift indicator was working, so ill do what you said, wait til it acts up and see the v's then. Its funny, it only wants to act up when i want to drive it, but when i go to work on it, it works fine, ironic. Ill keep ya posted. Thanks for everything though.

hey jeremy, got er on the volt meter, it is IN FACT losing voltage at the trans fuse when it starts acting up... So does this mean i just need to rerun that pink wire all the way, i havent found any breaks, cracks burns etc... in the wire itself? if i do just go ahead and install the new ign switch would i still have this problem? thanks

If you replace the switch, you shouldn't have the problem for some time. For some reason some of them have problems with powering the trans wire. My 96 with over 220k miles has never had a problem, while a buddies 96 had this problem at around 100k miles.

well, put in the new switch, got my tahoe back! just wanted to say thanks man, big help!