With 423 rwhp, you should be in the low to mid 14's.
I ran 14.3's at 403 rwhp, and 7,160#, and with somewhere near 500 rwhp, I ran 13.69 @ 98.3 mph at 6,980#
Does the tranny really make that much difference? I would guess our trucks weigh pretty close the same. Mike, are you running the hummers, and 35's? I know you were a couple years ago, but didn't know if you switched them.........

I have limped my tranny maybe 8 times, and zinged it 50+ times. (A zing is when you let off the throttle quick enough, throw it in neutral for a few seconds, back in drive, and you on your way, and you don't need a computer reset.) A limp, you need to shut it down and reset the computer.
The last time I limped it, I thought it was done. It took maybe 10 resets over 3 days before it came out of limp mode. That was at the track when I ran the 13.69. She limped right near the end of the 1/4 mile, and would only go in 2nd or 3 gear.

 

I'm running Toyo 35" tires on the Hummer wheels.

 

i also test drove the 68rfe/6/7 combo and it is astonishing
u are right on it being qiuet i couldnt even hear the turbo!
but with the windows open driven slow in hot weather with that radiator fan on sounds like a bus
and these things sit so high! i could bearly get in it! but overall a awsome machine
the one we drove was list 46.5k slt trim cloth but it was pretty nice
i wouldve wanted the wood grain interior on it though
also it was a 2500 qc it had plenty a room for me in the back
have u seen how big the exhuast tip is? like 5 inch!

 

Canada switched over production to ULSD nationwide in June 2006.

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