4L60E no shift

Mason Cramer

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this is a case where pulling the tranny fuse just might get you home. wish I knew that when I blew my second tranny. I think I could have gotten home.

I agree that the harness is fine. so if you can command the truck to shift, does it actually shift? I'm not an expert by any means just learn from experience you know... to me it sounds like you have a mechanical problem inside.

Al
It only shifts when i put my scanner in control mode and use the shifting program to manually tell the solenoids to shift. Essentially I'm bypassing the PCMs logic shift points by hitting an upshift or downshift button. My understanding of this transmission since its electronic is that it will only shift when the 2 solenoids are supplied 12V in a combination. The combination of the 2 solenoids turned on and off is what tells the tranny what gear to shift to. So as long as my scanner can send the correct signal to each solenoid, and it shifts accordingly, my guess is that the internal transmission function of the transmission is working, it appears to be something upstream of the PCM that's not telling it to shift. I have spent so much time on this i just have no ides what else it could be lol. I'm definitely no expert either, but i thought i knew a lot more than this. It's really got me stumped.
 

kennythewelder

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Is the speedo working. The VSS and TPS are part of the control system that the ECM is looking for. If ether or both are not working then you will have issues. Just food for thought
 

stutaeng

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Can you get a service manual for it? I'm sure there's troubleshooting guides on them. They usually have a table with symptoms and possible causes and things to check. Also probably need to perform a line pressure check test, resistance check solenoids, etc.
 

Mason Cramer

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Is the speedo working. The VSS and TPS are part of the control system that the ECM is looking for. If ether or both are not working then you will have issues. Just food for thought
The speedo is not working. According to my bench testing and my scanner the TPS works. I have a new one from my other truck i put in with no luck either. THe VSS works when i bnech test it, And i bought a new one just in case, The scanner does not show any VSS response. Chased wires back and have also checked continuity between the plug and pins 29, 30 on C1 Blue plug of the PCM and it seems to be alright.
 

Mason Cramer

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Can you get a service manual for it? I'm sure there's troubleshooting guides on them. They usually have a table with symptoms and possible causes and things to check. Also probably need to perform a line pressure check test, resistance check solenoids, etc.
I have a Chilton's and Haynes manual for the truck but cannot find enough info about the 4L60e in them. Haven't performed a line pressure check but i do know that when i unplug the 13pin connector to the tranny and drive it, it is running at full line pressure as it shifts from 1st to 3rd gear quite harshly as it would without the pressure regulator having power. I only pulled the pan off to change the fluid and filter while the motor was out, so i didn't check the solenoids physically, but my scanner shows me no faults with each individual solenoid and i can test each one independently without issue or delay.
 

kennythewelder

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The speedo is not working. According to my bench testing and my scanner the TPS works. I have a new one from my other truck i put in with no luck either. THe VSS works when i bnech test it, And i bought a new one just in case, The scanner does not show any VSS response. Chased wires back and have also checked continuity between the plug and pins 29, 30 on C1 Blue plug of the PCM and it seems to be alright.
I suspect the no response from the vss is the issue. I blew up my trans about 3 months ago. After the rebuild, it wouldnt shift into OD at WOT. I also noticed the speedo would jump around at the same point. The trans shop replaced the vss and problem solved. Its been good since, except I blew up the trans again. The trans shop had the line pressure cranked up to much. The rebuilt ot again, bit this time I had them replace the line pressure solenoid with an o OE replacement. None of the second rebuild cost me anything. Between the corvette servos, line pressure turned up, HD master rebuild kit, hardened sunshell, and shift kit, it was just to much for the trans to handle. Without the shift kit and the line pressure being back to OE, its all good now.
 

Mason Cramer

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I suspect the no response from the vss is the issue. I blew up my trans about 3 months ago. After the rebuild, it wouldnt shift into OD at WOT. I also noticed the speedo would jump around at the same point. The trans shop replaced the vss and problem solved. Its been good since, except I blew up the trans again. The trans shop had the line pressure cranked up to much. The rebuilt ot again, bit this time I had them replace the line pressure solenoid with an o OE replacement. None of the second rebuild cost me anything. Between the corvette servos, line pressure turned up, HD master rebuild kit, hardened sunshell, and shift kit, it was just to much for the trans to handle. Without the shift kit and the line pressure being back to OE, its all good now.
Lol sounds like even your beefed up built one wasn't enough to keep the 4L60e alive. I also suspected the VSS, But i can't seem to figure out why. I changed the sensor and the wiring is fine according to the meter... Still no change.
 

kennythewelder

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Lol sounds like even your beefed up built one wasn't enough to keep the 4L60e alive. I also suspected the VSS, But i can't seem to figure out why. I changed the sensor and the wiring is fine according to the meter... Still no change.
All of this started with me, when the rear end went out. I broke the open carrier bearing mount. Rebuilt the diff my self, and put an Eaton truetrac, with 373s. Had 342s. 1 and 1/2 weeks later I blow the sunshell. IMO I think the trans shop just took the 4L60E to far. Its all good now. I run the hell out of the truck, but hell Im only at about 325 HP. And I almost never tow anything. I have less than 300miles on the 2ed rebuild. But hey, the trans shop gave me 2 years, 24,000 mile warranty. I went back monday for my 2 week check up, and the owner said, well I will see you when you blow it up again. Man I hope that dont happen. I am guna run it hard though, thats just how I drive.
 

stutaeng

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I have a Chilton's and Haynes manual for the truck but cannot find enough info about the 4L60e in them. Haven't performed a line pressure check but i do know that when i unplug the 13pin connector to the tranny and drive it, it is running at full line pressure as it shifts from 1st to 3rd gear quite harshly as it would without the pressure regulator having power. I only pulled the pan off to change the fluid and filter while the motor was out, so i didn't check the solenoids physically, but my scanner shows me no faults with each individual solenoid and i can test each one independently without issue or delay.
Those manuals are for pretty basic/general repairs. I have a Haynes but don't recall any meaningful information for tranmission diagnostics. I'm thinking of the ATSG, etc.

The VSS should be pretty easy to check, I think. Any basic handheld scanner with live data should give a reading of the vehicle speed. If it's showing an accurate speed while driving, then most likely not the VSS.
 
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