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4l80e (first gen?) Hard shift issues

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Bare Foot Garage Enthusiast

Bare Foot Garage

Posted
Posted

Hey all,

 

I have a k2500 suburban with the 454 v8 and 4L80e (first gen I believe since cooling lines are side by side into trans body)

 

I do not have reverse (so could be reverse servo pin) but have heard if no reverse won't have low gear (1st) when shifted manually and seems I have that still.

 

So not sure if electrical issue where linkage connects to electric switch on outside body of trans. Or it's the electrical connections that go into the trans for the solenoids internally. Or it's the actual gears and bands etc inside.

 

Anyone else have no reverse, and hard shift between 1st and 2nd (and sometimes 2nd to 3rd) when in drive?

 

1st to second shifts hard around 2500 RPm or so. Which seems high to me.

 

So I am leaning towards besides obvious issues like solinoid, servo pin etc. That something internally is "binding" the when pressure gets higher then needed it "pops" and shifts.

 

Like when strut bearings bind when turning before the force breaks em free again.

 

Any help or ideas would be great! I havnt dropped pan, changed filter or fluid yet. Or taken electrical connector off side that goes inside (which I know can leak with time and short out connections and cause problems)

 

Thank you in advance.

 

Mr. Kate

Bare Foot Garage (On YouTube)

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

I'm having the same problem with the same trans but I still have reverse. I scanned it this afternoon and noticed the new neutral switch I put in is showing the pcm that its in park/neutral no matter what gear its in but not sure if that will cause the shifting problems I have. I had to replace the complete engine/ trans wiring harness and the internal trans harness as well as the neutral switch and it was fine before that. I'm pretty sure my converter is locking as soon as it shifts to 2nd gear causing really hard shift. I really need to take it to a trans shop and have them do a deep scan to figure it out I think, I also had a code for a shift solenoid and the torque converter. I'm positive my problems electrical but you may have more going on where you have no reverse. Any ideas guys?

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

it doesn't look like we are going to get any suggestions here but my thoughts are you should start by having it scanned with a scan tool that can read trans codes and data and a tech that can interpret what they see. that may not be an easy thing to do unless you go to a trans specialist which around me are pretty scarce

  • 2 months later...
J F New Member

J F

Posted
Posted

Unplug the connector on the side of the trans. Do you see red fluid? You shouldn't see any fluid at all. The connector is known to crack internally allowing trans fluid into the connector. This will cause a host of issues with shift/ing. 

 

You'll need to drop the pan and replace the wire harness internally. Easy DIY. While in there change both Shift solenoids and turn up the force actuator a 1/2 turn. New fluid and filter as well.

J F New Member

J F

Posted
Posted

Unplug the connector on the side of the trans. Do you see red fluid? You shouldn't see any fluid at all. The connector is known to crack internally allowing trans fluid into the connector. This will cause a host of issues with shift/ing. 

 

You'll need to drop the pan and replace the wire harness internally. Easy DIY. While in there change both Shift solenoids and turn up the force actuator a 1/2 turn. New fluid and filter as well.

Bare Foot Garage Enthusiast

Bare Foot Garage

Posted
  • Author
Posted

Thanks  I havnt gotten the connector apart yet. Didn't know how and don't wanna break it *laughs*

 

But have the valve body, filter etc out. So will check soon.

 

 

 

Found out tho the check bearings in the valve body had elongated and deformed some of the holes they were suppost to sit in tho. Well in the gasket they did...

 

 

 

So have those parts on order too.

 

 

 

Thanks again for all the help!

 

 

 

Mr. Kate

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

LoL, you can't figure out the connector but you have the valve body apart!  GO Mr Nate

richard wysong Senior Enthusiast

richard wysong

Posted
Posted

A piece of pipe or a socket that fits over the plug n the side of the trans will release the tangs so the plug can be pushed into the case

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