New Tahoe. New problems

[05Single]

I had to replace the flexplate in my express van, it was cracked almost all the way around. Starting out as a small little tinging sound. My buddy, who's a mechanic kept saying it sounded like a loose cat converter shield. Kept getting louder. Does yours kind of sound like that or something similar. View attachment 71838

Actually a common problem with these trucks. Mine makes a noise sometimes. But I know it's the exhaust shield and not the flex plate or anything in the trans or motor. Pretty distinct noise.

 

[rockola1971]

Its on the drier, unplug it and check for continuity on the switch terminals. I believe it closes the circuit when the pressure is high enough and not the other way around, but you can check first. Anyway, if its normally open and closes with pressure, just jumper wire/paper clip the two terminals in the connector that you unplugged and you can temporarily bypass it. Make sure it doesnt ground to anything and if it fixes it, replace the switch and dont leave the jumper in lol. If its normally open when the system has pressure (which I don't think is the case) you can just leave it unplugged.

You cant "short it out". You can short it to ground but that is what the signal is that the PCM is looking for. When the pressure is above 20 or 30 PSI (I cant recall the exact #) then the switch is closed and gives a ground to the PCM. You can jump the plug terminals and your clutch will engage if you have the A/C on.

 

[mizzouguy]

@rockola1971 what you just described is the same as what i said lol. I wasnt sure if open circuit made the control unit happy or closed circuit.

 

[rockola1971]

@rockola1971 what you just described is the same as what i said lol. I wasnt sure if open circuit made the control unit happy or closed circuit.

And thats why I quoted this part "just jumper wire/paper clip the two terminals in the connector that you unplugged and you can temporarily bypass it. Make sure it doesnt ground to anything"

So why should anyone "make sure it doesnt ground to anything"? That statement right there insinuates that there is 12vdc+ considering you cant short ground to ground and THAT is exactly the only signal on that circuit....GROUND. The circuit is ground seeking. The pressure switch is indeed a Normally Open switch with two wires attached. One wire goes directly to ground and the second wire leads directly to the PCM input "low pressure cutoff". If the PCM sees a ground then it is happy and continues to energize the clutch and keep the compressor compressing. If the PCM does NOT see a ground then it translates this as the pressure is too low "there must be a leak" and cuts of the electro magnet clutch in the compressor to protect the compressor because if the refrigerant leaked out then so did the lube oil for the compressor that is mixed with it.

 

[mizzouguy]

Jesus christ dude...isolating the circuit so that it doesnt short out, regardless of positive or negative, is just good practice. What if it didn't ground? Not everyone is as smart as you must be. Get off my ass and your high horse. I was just trying to help the op.

 

[Newkon]

So I dropped my truck off and told the guy that I believe it has a bad flex plate. Told him that I'm not 100% sure. I have reason to believe that they didn't even check it before putting it on the lift. Now they just called me and said that my flex plate was fine. All bolts were tight. I asked them if they checked all the exhaust manifold bolts and shield bolts and they said they were good.

So onto the real issue I have.. they said that they think it's the torque converter. I don't think it's the torque converter because there was no transmission slip at all when driving. Just the noise of a bunch of marbles. I believe they are just trying to screw me over. What do you guys think??

 

[YukonandtheHOE]

So I dropped my truck off and told the guy that I believe it has a bad flex plate. Told him that I'm not 100% sure. I have reason to believe that they didn't even check it before putting it on the lift. Now they just called me and said that my flex plate was fine. All bolts were tight. I asked them if they checked all the exhaust manifold bolts and shield bolts and they said they were good.

So onto the real issue I have.. they said that they think it's the torque converter. I don't think it's the torque converter because there was no transmission slip at all when driving. Just the noise of a bunch of marbles. I believe they are just trying to screw me over. What do you guys think??

The thing to do is have the guys pull the inpection cover, unbolt the Torque and see if the flex plate will wiggle independently. If it is infact a broken plate that is.

 

[YukonandtheHOE]

What is the process for bypassing the low pressure cutoff switch?

It's as simple as unpluging the pig tail and use a small piece of wire bared on both sides to jump the pigtail then tape it up!

 

[Newkon]

I am having no issues that would make me believe its the torque converter. The transmission isn't slipping, studdering, or acting abnormal in any way. I have searched for countless hours on the internet searching for symptoms of a bad torque converter and listening to videos of guys with a bad torque converter and can't mimic the sound that i am having. The closest that i was able to find was with someone with a cracked flex plate. It shifts smooth and the motor runs perfect. What other parts would mimic the same sound as a bad flex plate? Im stumped and can't justify paying this guy $650 to replace the torque converter. Maybe he didn't inspect my truck well enough? I am halfway tempted to just take the truck back and try to find the source of the problem myself. I was reading that it could be a number of things, including a bad starter, loose manifold bolts or shield bolts.. Sorry to be bothersome, but i just can't convince myself. I would have to pay the guy for whatever he did(if he even did anything) and thats where I'm hesitant. The only reason i took it to the guy is because my family has dealt with him and i didn't feel like unbolting the tranny and transfer case to slide it back enough to inspect and replace the flex plate.

Also, wouldn't I find metal shavings or pieces of the torque converter in the tranny pan if I pulled the plug?

 

[Badwrench]

I'll take a shot in the dark. I have once fixed similar which turned out to be a missing return spring(after tranny rebuild on older GM350). The springs purpose is to push the starter gear forward after the engine starts. If is is missing/broken the started gear is free to reengage and be 'tinged' back off the flywheel.
Test this theory by seeing if you don't hear marbles in your exhaust while taking off from stop in reverse. Good Luck !