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4l65 to 4l80 awd swap VSS ISS

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Old 05-13-2018, 07:43 PM
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Default 4l65 to 4l80 awd swap VSS ISS

Anyone that has done this swap please put me on the right path. I've completed the swap but I'm questioning which location of the VSS and ISS I used.

If I remember correctly, my 03 SSS 4l65e harness only had one VSS connector which is at the transfer case. The 4l80e has 2 speed sensors front and rear.

So Now I have 3 speed sensors total. I added a second speed sensor harness and pinned it to 22 and 23 at the ECM. Do I connect the factory harness speed sensor to the most rear VSS in the transfer case and the new added harness to the 4l80 most forward ISS and leave the 4l80 rear sensor unconnected?

Only reason I ask is because I currently have the stock harness connected to the transfer case speed sensor and my added harness to the 4l80 rear VSS and the 4l80 forward ISS is unconnected. I'm having shifting/limp mode issues and I believe it's the speed sensor communication or lack of causing my issues. Anyone that has done the swap on a 4wd/awd please respond, thanks.
Old 05-14-2018, 07:52 AM
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It has been awhile but I believe I have 2 connected to my tcase and then the new added one to the front of the trans.
Old 05-14-2018, 09:59 AM
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I just got my Nelson 4L80e harness and it says the new sensor that goes to pin 22/23 goes to the forward most sensor on the 4L80e.

I have a 2wd truck, but my understanding is the 4wd models have a blockoff on the rear hole and the sensor is in the transfer case. So from the bellhousing moving towards the rear, it would be the new added sensor, blockoff hole, then stock sensor in the transfer case
Old 05-15-2018, 08:22 PM
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Thanks guys, I moved my added speed sensor harness to the forward ISS on the 4l80e and still no change in my trans shifting gremlins.
Old 05-16-2018, 03:11 AM
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Originally Posted by SDjeff619
Thanks guys, I moved my added speed sensor harness to the forward ISS on the 4l80e and still no change in my trans shifting gremlins.
what kind of gremlins?

The vss is the rear sensor and the front one is the ISS.

Old 05-16-2018, 10:29 AM
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Originally Posted by madmann26


what kind of gremlins?

The vss is the rear sensor and the front one is the ISS.

Yes, the ISS is in the front.

Soo, the trans is a brand new built 4l80e from Hughes Performance with one of their 3k stall converters.

The first 50 miles lightly cruising around town it seemed to be shifting fine in DRIVE, but when I reached 50-65 mph, it felt like either the converter was locking and unlocking or the trans was shifting back and forth between 3rd and 4th gear. When commanding 4th gear, the surging went away.

A few days later, the trans went into limp mode stuck in second gear and the pressure control solenoid showed 0v.

I still have yet to pull the pan to check solenoids and internal harness due to free time away from my new born son lol.

Regards to the surging, I did read that if all speed sensors don’t read the same along with tire size properly set in hptuners it can cause multiple solenoid operating issues.
Old 05-16-2018, 04:09 PM
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Originally Posted by SDjeff619


Yes, the ISS is in the front.

Soo, the trans is a brand new built 4l80e from Hughes Performance with one of their 3k stall converters.

The first 50 miles lightly cruising around town it seemed to be shifting fine in DRIVE, but when I reached 50-65 mph, it felt like either the converter was locking and unlocking or the trans was shifting back and forth between 3rd and 4th gear. When commanding 4th gear, the surging went away.

A few days later, the trans went into limp mode stuck in second gear and the pressure control solenoid showed 0v.

I still have yet to pull the pan to check solenoids and internal harness due to free time away from my new born son lol.

Regards to the surging, I did read that if all speed sensors don’t read the same along with tire size properly set in hptuners it can cause multiple solenoid operating issues.
The electronics and harness are cheap and easy to swap.

I assume the wiring is gtg?
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