I just picked up a lifted 99 Tahoe with a weak tranny. Rather than swap in another 4L60, thought about a 4L80. Parts converting it isn't the problem, its the ECM and wiring. I remember seeing it somewhere someone swapped the two, redid the wiring on the truck and though he used a 350/4l80 ECM and not get the stock one reflashed. I guess the wiring pin out is different between 1500 and 2500/3500s. How different is the wiring off the ECM between the two? Would it be easier to swap ECMs, or get current one reflashed and get adapter harness?
CK5
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Swap 4L60 to 4L80
- Thread starter b454rat
- Start date
anyone?
There are some significant differences operating system in the PCM. The 99/00 PCMs can be re-flashed by EFIlive but you'd be just as well off to just swap the PCM out with one from your donor vehicle. Re-learning the vehicle security system isn't a huge deal but it does take a little over 2 hours without EFIlive or a Tech 2 to modify the key cycle counters and timers.
As for wiring differences the biggest difference between the two is the addition of input and output speed sensors on a 4l80e. The bulk of the main harness for the shift solenoids is the same between the two but a 4l80e does have a different connector than a 4l60e. I believe that neutral / safety / backup switch and the shifter position switches interchange but don't hold me to that. You may need to change the connectors to make that play nice as well.
Ultimately you'll want to find a 99/00 5.7L/4l80e PCM, engine and transmission harness then swap it all in with the transmission, re-learn the vehicle security and you should be good to go. Keep in mind that the 4l80e has a 32 spline output shaft, so you'll need to swap your t-case input shaft to match. Your driveshafts should interchange no problem and you shouldn't have any clearance issues. I believe you will need to change your transmission cooler lines as well. The shifter bracket on the transmission may also be unique so be prepared to change it too.
As for wiring differences the biggest difference between the two is the addition of input and output speed sensors on a 4l80e. The bulk of the main harness for the shift solenoids is the same between the two but a 4l80e does have a different connector than a 4l60e. I believe that neutral / safety / backup switch and the shifter position switches interchange but don't hold me to that. You may need to change the connectors to make that play nice as well.
Ultimately you'll want to find a 99/00 5.7L/4l80e PCM, engine and transmission harness then swap it all in with the transmission, re-learn the vehicle security and you should be good to go. Keep in mind that the 4l80e has a 32 spline output shaft, so you'll need to swap your t-case input shaft to match. Your driveshafts should interchange no problem and you shouldn't have any clearance issues. I believe you will need to change your transmission cooler lines as well. The shifter bracket on the transmission may also be unique so be prepared to change it too.
