View Full Version : GM 6L80 transmission in a '99?
12-26-2011, 01:00 AM
Can a GM 6L80 transmission be swaped into a 99 nbs with a 5.3?
12-26-2011, 02:39 PM
I guess, what I'm asking is: Has anyone done this? Did they use their stock ECM and reprogram, or go with another ECM?
I want better gas mileage, and I'm guessing if I could add 2 more gears I'd be golden since I swapped my axles to 4.10 gears already.
12-26-2011, 03:49 PM
will not increase gas milage any the final drive on the 6l and the 4l is pretty much the same only difference is the first 2 gears that are lower. the 6l has a 4.02 ist gear where as the 4l has a 3.08 and the 6th gear in the 6l is a .67 and the 4th gear in the 4l is a .69 so there is virtually no difference in the gearing in overdrive.
12-26-2011, 05:37 PM
Along the same lines, can it be used in place of a 4L80E behind a 5.7? Can the blackbox pcm support the 6L80E?
12-26-2011, 07:23 PM
no the 6l80e has its own TCM inside the trans it would require a pcm swap and alot of wiring its really more than its worth doing. you are looking at 4 gran for a trans to start with. plus electronics tuning and wiring and installation modifications to the crossmember.you have a 4l80e you already have a better trans in the first place.
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