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Please Help With 2004 4L80E Transmission

05 2500 hd 6.0

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05 2500 hd 6.0 New Member

05 2500 hd 6.0

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Evening , I have been working on a customers 2004 Chevrolet 2500HD. It has the 6.0 engine and 4l80E transmission. I've been building automatic transmissions for 30+ years, and he brought it to me to rebuild the 4l80E transmission in it for him, and I just got it done, and was test driving it, and noticed another issue with it, and I would like to have some input on what exactly needs fixed to cure it. The transmission shifts beautiful after getting it done, but the problem appears when coming to a stop. When coming to a complete stop, and immediately give it throttle to take back off, it seems as if it is still in 2nd gear momentarily ,and then kicks back to 1st gear, and that makes it jerk. While doing this, I noticed that the speedometer is slow coming back down to zero, it doesn't fall back to zero immediately when coming to a stop. So I tested it again, and I completely stopped, and waited for the speedometer to come back too or just below zero, and it DOES NOT have the problem if you do that, it takes off in first and shifts beautiful just like it is supposed to, but if you come to a stop, and immediately take back off, without waiting for the speedometer to come completely settle back to, or just below zero, it will take off in 2nd and kick down into 1st everytime, causing it to jerk when taking off. 

Now, can someone please help me with what is causing this issue? I need to get it fixed before letting the customer have his truck back. I put new speed sensors in the transmission while I had it out. Could speedometer be the problem, since it is "slow" to come back to zero, and the truck still thinks it's in motion, when in fact it's at a stop? I would appreciate some advice on this so I can get it fixed and back to the customer. Thank You!

  • 3 months later...
gmtech4 Senior Enthusiast

gmtech4

Posted
Posted
Evening , I have been working on a customers 2004 Chevrolet 2500HD. It has the 6.0 engine and 4l80E transmission. I've been building automatic transmissions for 30+ years, and he brought it to me to rebuild the 4l80E transmission in it for him, and I just got it done, and was test driving it, and noticed another issue with it, and I would like to have some input on what exactly needs fixed to cure it. The transmission shifts beautiful after getting it done, but the problem appears when coming to a stop. When coming to a complete stop, and immediately give it throttle to take back off, it seems as if it is still in 2nd gear momentarily ,and then kicks back to 1st gear, and that makes it jerk. While doing this, I noticed that the speedometer is slow coming back down to zero, it doesn't fall back to zero immediately when coming to a stop. So I tested it again, and I completely stopped, and waited for the speedometer to come back too or just below zero, and it DOES NOT have the problem if you do that, it takes off in first and shifts beautiful just like it is supposed to, but if you come to a stop, and immediately take back off, without waiting for the speedometer to come completely settle back to, or just below zero, it will take off in 2nd and kick down into 1st everytime, causing it to jerk when taking off. 

Now, can someone please help me with what is causing this issue? I need to get it fixed before letting the customer have his truck back. I put new speed sensors in the transmission while I had it out. Could speedometer be the problem, since it is "slow" to come back to zero, and the truck still thinks it's in motion, when in fact it's at a stop? I would appreciate some advice on this so I can get it fixed and back to the customer. Thank You!

Did you reset shift adapts with scanner? I doubt that is it but have to ask ,,,,, this is real interesting , I’ve rebuilt a ton of 80s and never came across this , my head hurts thinkin of this lol

Did you have a scanner watching data PIDS ?


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05 2500 hd 6.0 New Member

05 2500 hd 6.0

Posted
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Posted
21 hours ago, gmtech4 said:


Did you reset shift adapts with scanner? I doubt that is it but have to ask ,,,,, this is real interesting , I’ve rebuilt a ton of 80s and never came across this , my head hurts thinkin of this lol

Did you have a scanner watching data PIDS ?


Sent from my iPhone using Tapatalk

Hi Rob, we didn't reset the shift adapts, but we did get it fixed. We adjusted the EPC Solenoid in 3/16 of a turn, and got Idle pressure up to 60 psi, instead of 35 psi that it had orginally, and also instaled the Sonnax 34200-14K Line to Lube valve in the pump, and it worked perfectly after doing those two modifications. Hope this helps.

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