i'm open to any guesses, I don't know what to check anymore. Well vince i checked voltage at the trans fuse in the dash, and ran the truck around with a meter up to it and got almot 14 volts the whole time, so that means the ignition switch is good right? And I though no power equals limp mode which is only 3rd gear? I pulled the fuse and drove the truck and still had 2nd and 3rd. Keep the ideas coming I don't know what to check, what is overrun?

 

You should have manual 2nd in limp mode. You need to get break out box to run the trans on it's own. This will eliminate the internal harness and solenoids. This will point you in the direction of the outside harness, grounds, PCM, OR mechanical issues like a sticky valve, etc. You should purchase an ATRA book from a supplier, (about $18.00-$20.00), and it will help you diagnos your problem. There are a tremendous amount of variables that can cause this problem. Overruns are a set of clutches in the input drum. I doubt there is a problem there.

Good luck.

 

Where would I get a breakout box from? I do think there is a bigger underlying issue because the truck has been shutting off too. The radio will shut off totally and the battery runs dead, the idle is really high. Sounds to me like a shorted ground somewhere. Not sure if thats the issue tying everything together but i'm gonna try to hunt down this bad ground and see if that does anything.

 

Have you tried to tag the power wire from the computer to the trans while driving to see if it get interrupted?

Ignition switch or a ground I'm pretty sure is where its at. With the turning off and on of your accessories it has to be one of the two if I had to guess. Vince

 

If you have multiple codes change your ignition switch.They are a real problem in GM vehicles.The problem is when you crank the car voltage drops under 8 volts and sets all kinds of trans codes.Thats were i would start first. [Non-Sponsor Info Removed]

 

I found a broken ground on the front of the block. DIdn't fix the problem though. I'll try ignition switch next, you know where it's at on my 98 truck? In the column or what?

 

Yes it is in the column. It takes about an hour to change.

 

Ok I took the ignition switch out of the equation. I took the trans fuse in the dash which runs the dash gauges and trans and jumped it directly to 12v hot. So that should bypass the ignition switch, and there is no change in the trans problems. What else guys lol. I'm running out of systems to check here. I took almost the whole engine harness apart and found nothing but that one broken ground and that might of been the truck shutting off problem but nothing fixed the trans.

 

I'm not ignoring suggestions, first off where am I gonna get a tech 2 from a gm dealer, I just walk in and say can I borrow this? And I already asked where to get a break out box from and nobody answered, it's not like a break out box is an off the shelf part here. And no i'm not changing parts at random I troubleshoot and think I find the problem then when i fix it, turns out not to be the problem. I've checked all the solenoids, the voltages, pretty much all the wiring in the system. I'm mainly asking for peoples opinions who know more about the inner workings, I am not familiar with all this electronic trans crap. And I have listenend to all your opinions and tried to test for them, but with no success. and how can i change my diagnostic troubleshooting lol. I find out how the system works and I test that part. How is it i'm wrong testing all the electrical components when all you suggest to check them?

 

I hate changeing parts but I thought i've found the problem thats why i changed the one solenoid and the pcm. I can take it to a shop but I don't want to spend the money cause i'm just wanting to fix it for now, i'm putting an lq4 in it eventually. And i'm the kind of guy that I need to know what the problem is, for my own knowledge so I can help somebody else out if it happens to them too.

 

Would a trans shop use a breakout box? Or would they just hook the scanner up? Unless they use a special type of scanner, I already know i'm getting alot of tranny codes, pretty much every tranny code there is. I found a place here that does free diagnostics but don't know if they gonna hook scanner up and say you got 7 codes, you need trans rebuilt. Ya know.
I'm thinking I fixed the shutoff problem, think it was that ground but i'd have to drive it more to find out. Although i did get a misfire code that the scanner pulled up so maybe thats keeping it in limp mode if it's misfiring. Hmm might be something to look at, not sure why it would be misfiring i replaced the plugs and wires, maybe the "distributor" is going bad. I'll look into taking it to that shop tomorrow and see what develops.

 

you dont have a distributor, you have coil packs

 

My truck has a crap 4.3 vortec and that distributor is exactly what it looks like. Maybe i'll look into and see if I can clean or change the cap out.

 

lol i thought he was running a l98 for some reason. my bad

 

LOL

 

Finally got it figured out, it was three problems. It was the ignition switch that fixed the gauge problems, the ground fixed the shutting off probs and the distrubutor cap/rotor caused a misfire and kept trans in limp mode. I cleaned corrosion off cap and rotor, bypassed the ignition switch and trans works good now. Thanks guys.

 

This is another way to check it if you do not have access to the proper tools , ( Tech 2, Breakoutbox) Disconnect the plug to the trans. supply voltage to A solenoid , you control the ground to the solenoid. If you have voltage and you ground it ,the solenoid then you will start off in first gear. drive around the block in first gear if it toggles in and out of gear then you have a trans issue, if it stays in gear then you have an electrical issue. PS , the computor will set codes and the trans will be at full pump pressure when you do this.