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4l80e Wont Shift Out Of 2nd


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#1 joshxxl

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Posted 01 November 2008 - 06:33 PM

Ok here is the issues. Last week my 1995 k2500 4x4 suburban went into the 2nd gear protect mode. I did some research online and determined that my rear output VSS took a crap. I changed. It is located on the Transfer case. While I was under the SUV I also changed the Input VSS on the Front drivers side of the trans, just to be sure I corrected the problem. I then unhooked my battery to remove the code. Restarted the SUV drove it around. Shifted great no isses until after about 40 min. the SUV went back into the 2nd gear protect mode. I pulled over and shut it off and waited a couple of minutes to reset the computer, so I could get it home. When I got home checked the code. 72 output speed sensor. I grabbed my test light. Unplugged the rear output sensor and while the vehicle was running tried to get my light to light up no luck. I then went to the cpu under the dash on the passangers side. I found the green wire with the black line. I tested it at the cpu, my test light lit up. I then found the wire just before it exited the cab. I poked my test light into the wire and it lit up. I then went under the SUV traced the wires back to a connection near the front of the trans on top of it. I unplugged the wire and tested inside the connection no luck, my light did not light up. I then went about an inch up the wire and stabbed my test light in and it did not work. My question is should it be lighting up at the rear VSS? Do not want to take to the dealer but if I have to I will. Is it possible that the wire is broke somewhere between where it exits the cab and the connection on top of trans? Please help

#2 joshxxl

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Posted 02 November 2008 - 07:09 AM

Ok here is the issues. Last week my 1995 k2500 4x4 suburban went into the 2nd gear protect mode. I did some research online and determined that my rear output VSS took a crap. I changed. It is located on the Transfer case. While I was under the SUV I also changed the Input VSS on the Front drivers side of the trans, just to be sure I corrected the problem. I then unhooked my battery to remove the code. Restarted the SUV drove it around. Shifted great no isses until after about 40 min. the SUV went back into the 2nd gear protect mode. I pulled over and shut it off and waited a couple of minutes to reset the computer, so I could get it home. When I got home checked the code. 72 output speed sensor. I grabbed my test light. Unplugged the rear output sensor and while the vehicle was running tried to get my light to light up no luck. I then went to the cpu under the dash on the passangers side. I found the green wire with the black line. I tested it at the cpu, my test light lit up. I then found the wire just before it exited the cab. I poked my test light into the wire and it lit up. I then went under the SUV traced the wires back to a connection near the front of the trans on top of it. I unplugged the wire and tested inside the connection no luck, my light did not light up. I then went about an inch up the wire and stabbed my test light in and it did not work. My question is should it be lighting up at the rear VSS? Do not want to take to the dealer but if I have to I will. Is it possible that the wire is broke somewhere between where it exits the cab and the connection on top of trans? Please help

The suburban has 150,000 miles on it and when it first starting having trouble I changed the trans filter and fluid.
Anyone....

#3 Ranger

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Posted 02 November 2008 - 07:15 AM

You may be testing the wrong wire, I don't think it's possible for it to "terminate" in the middle of the line, either the whole thing has power or it doesn't...I'd make sure you're testing the right wire cause there are a few similar color codes in the chassis...Best thing to do is get a book on it with an electrical diagram and find out where the VSS terminates in the cab.

On second thought, you should try a resistance reading? I don't see how a wire can just spontaneously break unless it got rotted out...

Edited by Ranger, 02 November 2008 - 07:17 AM.


#4 joshxxl

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Posted 02 November 2008 - 07:47 AM

Ok I might just be an idiot. Some one please tell me.
When under the suv yesterday I noticed that the transmission plate said hydromatic turbo. I didnt give it much thought until this morning. Is the 4l80e and hydromatic turbo the same transmission? If not how do I tell if I have the turbo 350 or 400? The rear speed sensor I bought was for the 4l80e. I could have the wrong speed sensor.

#5 redvett

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Posted 02 November 2008 - 09:13 AM

You stated the problem started AFTER you changed the filter & oil, so go back to the source and check for any broken or unhooked wires on the valve body.

Ok here is the issues. Last week my 1995 k2500 4x4 suburban went into the 2nd gear protect mode. I did some research online and determined that my rear output VSS took a crap. I changed. It is located on the Transfer case. While I was under the SUV I also changed the Input VSS on the Front drivers side of the trans, just to be sure I corrected the problem. I then unhooked my battery to remove the code. Restarted the SUV drove it around. Shifted great no isses until after about 40 min. the SUV went back into the 2nd gear protect mode. I pulled over and shut it off and waited a couple of minutes to reset the computer, so I could get it home. When I got home checked the code. 72 output speed sensor. I grabbed my test light. Unplugged the rear output sensor and while the vehicle was running tried to get my light to light up no luck. I then went to the cpu under the dash on the passangers side. I found the green wire with the black line. I tested it at the cpu, my test light lit up. I then found the wire just before it exited the cab. I poked my test light into the wire and it lit up. I then went under the SUV traced the wires back to a connection near the front of the trans on top of it. I unplugged the wire and tested inside the connection no luck, my light did not light up. I then went about an inch up the wire and stabbed my test light in and it did not work. My question is should it be lighting up at the rear VSS? Do not want to take to the dealer but if I have to I will. Is it possible that the wire is broke somewhere between where it exits the cab and the connection on top of trans? Please help

The suburban has 150,000 miles on it and when it first starting having trouble I changed the trans filter and fluid.
Anyone....



#6 joshxxl

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Posted 02 November 2008 - 11:03 AM

Ok I might just be an idiot. Some one please tell me.
When under the suv yesterday I noticed that the transmission plate said hydromatic turbo. I didnt give it much thought until this morning. Is the 4l80e and hydromatic turbo the same transmission? If not how do I tell if I have the turbo 350 or 400? The rear speed sensor I bought was for the 4l80e. I could have the wrong speed sensor.


The problem started before I changed the filter and oil. The reason I changed the fluid is to rule out a clogged filter as a possability.
I also figured out that I do have the 4l80e.

#7 redvett

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Posted 02 November 2008 - 11:30 AM

GM has a patent on the name Hydramatic and RPO "MT1" is the 4L80E. I suggest you find someone with a live data scanner Tech 2 or other brand an find out what is really wrong. Throwing parts at it is wasteful.


Ok I might just be an idiot. Some one please tell me.
When under the suv yesterday I noticed that the transmission plate said hydromatic turbo. I didnt give it much thought until this morning. Is the 4l80e and hydromatic turbo the same transmission? If not how do I tell if I have the turbo 350 or 400? The rear speed sensor I bought was for the 4l80e. I could have the wrong speed sensor.


The problem started before I changed the filter and oil. The reason I changed the fluid is to rule out a clogged filter as a possability.
I also figured out that I do have the 4l80e.



#8 ujtruck

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Posted 02 November 2008 - 11:44 AM

I just like to help you, but I am no transmission expert in anyway...however here is what I learn from my friend's shop.

Normally If you have VSS issue, you also will get ABS light on too. do you have that....?

then for sure 1st thing to check is your VSS wire and the sensor, etc. normally sensors will not go bad, but wires do - (and sensors go bad too ).

Edited by ujtruck, 02 November 2008 - 11:52 AM.

 gr_chug.gif


#9 joshxxl

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Posted 02 November 2008 - 05:56 PM

I just like to help you, but I am no transmission expert in anyway...however here is what I learn from my friend's shop.

Normally If you have VSS issue, you also will get ABS light on too. do you have that....?

then for sure 1st thing to check is your VSS wire and the sensor, etc. normally sensors will not go bad, but wires do - (and sensors go bad too ).


ABS light has been on for the past year. My problem just started about 3 weeks ago. Tomorrow it will go to the stealership. I will keep everyone posted as to what they find. It just puzzels the heck out of me???? I know it isnt anything major. But when it comes to electrical I suck...

Love the forum. I will defenintly be on this site alot. I like to fix every little tick and pop my burb has. Ha Ha...
Keeps me out of the house and in the garage.

#10 ujtruck

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Posted 02 November 2008 - 06:45 PM

I just like to help you, but I am no transmission expert in anyway...however here is what I learn from my friend's shop.

Normally If you have VSS issue, you also will get ABS light on too. do you have that....?

then for sure 1st thing to check is your VSS wire and the sensor, etc. normally sensors will not go bad, but wires do - (and sensors go bad too ).


ABS light has been on for the past year. My problem just started about 3 weeks ago. Tomorrow it will go to the stealership. I will keep everyone posted as to what they find. It just puzzels the heck out of me???? I know it isnt anything major. But when it comes to electrical I suck...

Love the forum. I will defenintly be on this site alot. I like to fix every little tick and pop my burb has. Ha Ha...
Keeps me out of the house and in the garage.


Right ON! ABS light has been ON for year, ok thats mean, according to my mechanic buddy you have defective VSS , VSS wire or VSS buffer chip, this chip is located near passenger kick panel (white color little box, can be even some other color).

but he can be wrong as usual... :confused:

 gr_chug.gif


#11 redvett

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Posted 02 November 2008 - 06:45 PM

ABS light has been on for the past year. Why would you drive a vehicle with it not working? You should have fixed that first.

#12 grampadirt

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Posted 10 November 2008 - 01:42 AM

You need to do an ABS scan....might be as simple as a sensor on a wheel.I did,found it was the left front wheel.Changed the sensor,no more ABS light.Did you fix your tranny?

Gary

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#13 95Sierra2500

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Posted 10 November 2008 - 08:14 AM

ABS light has been on for the past year. Why would you drive a vehicle with it not working? You should have fixed that first.


My ABS light has been on in my '95 sicne I bought it 2 years ago. I know it's the passenger front wheel sensor. But I'm not dropping $250 on a hub when the bearing is in good shape. Oh, I also don't want to press all 8 of those studs out and pull them back in either.
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#14 grampadirt

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    something smells fishy around here

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Posted 10 November 2008 - 11:38 AM

Here's the good part,you don't have to replace the hub to change the sensor..I didn't.It's been 6 months since I did my left front and don't remember exactly how I did it however. Go to your local GM dealer and ask him to look on the computer for the sensor and you'll be able to tell from that what has to be done.I can remember when I bought mine I left the dealer with a long wire with a module on one end and a plastic plug on the other end all in a long plastic,sealed bag.I'm gonna be doing brakes on my Burb today or tomorrow and I will take some pics...I'll be replacing the rotors so I 'll get a good shot of the sensor.
ttyl,Gary

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#15 redvett

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Posted 10 November 2008 - 12:19 PM

You have to understand that the systems communicate back & forth through the UART buss and having one code can disable many other systems.
Start by fixing the ABS and then scan live data on the PCM for the transmission problem.

ABS light has been on for the past year. Why would you drive a vehicle with it not working? You should have fixed that first.


My ABS light has been on in my '95 sicne I bought it 2 years ago. I know it's the passenger front wheel sensor. But I'm not dropping $250 on a hub when the bearing is in good shape. Oh, I also don't want to press all 8 of those studs out and pull them back in either.






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