6.2L with 6L80


Registered User
Jan 28, 2022
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Papalote TX
Hello all, I have a Humvee that I installed a 6l80 behind the 6.2L and got to really give it a workout this weekend, I participated in the annual S. Padre Island beach cleanup.
We went 46mi down a FWD only beach and the sand was pretty soft for most of the 92 mile round trip run.
The 6L80 made a HUGE difference in its street-ability going from 2900 RPM with the TH400 @ 60 MPH to 1800 RPM and because the design is 50 years newer it is much more efficient as far as transferring power, the TH400 was a huge power sucking hole.
Anyway we dogged it real ******* the way down, high range and soft sand, doing around 35-40 at full throttle for about 30-35 miles while monitoring the trans on a laptop, the hottest we could get it was 205 deg, we sucked a ton of fuel!
On the way back we went into low range @ around 20-25 MPH and it was very happy at around 140 deg.
This truck weighs 7400lb + trailer and by the time we got back it was stacked very high with heavy wet sand laden trash! I wish I had taken more pictures.
I am real happy with the performance of the rather under powered 6.2L with the 6L80, I just recently picked up a GEP 6.5L center mount turbo engine with very low miles and believe it will be just the small amount of added power to make this rig really shine.
I installed a 6.6L LMM with the Allison 1000 in my other Humvee and that is a totally different animal!
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bilge rat
May 8, 2007
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Agreed on the th400... it's amazing the difference of having lockup and enough gear spread. Even a clunky old 4spd manual was a huge improvement with my 6.2L.