Just figured I’d throw this out there to the group.
BACKGROUND:
There are many reasons why folks love the 3.92 gears… (way lower 1st gear, lower reverse gear, better acceleration, etc) but for me I mainly was searching for ways to remove my highway drone from my Carven Competitor (which I love)!
Prior to this I had:
1) Solo Performane Mach 44 muffler (too quiet for me, and really the only loud sound was droning)
2) Carven Progressive (loud, but still not loud enough) with a fair amount of drone
3) Carven Competitor (louder still, and frankly the same drone as the Progressive)
In addition to (2) and (3) I also had installed the Mufflex Drone Supression pipe which made things a little better, but the truck was still frustrating to drive for more than 2-3 hours at a time.
I had heard good things about the Corsa Muffler, but it sounds more like a sports car than a V8 truck…
THE SOLUTION:
In general, 7th gear with a 3.21 runs at the same engine speed as 8th gear in the 3.92… which for me cruising at 65+ down the highway keeps my exhaust sounding loud and great with no drone!
What I ended up doing is reflashing my TCM to get rid of 8th gear, so now my truck only runs from 1-7th (giving me what amounts to be the same final gearing as I’d get with the 3.92).
Very happy with how things turned out, and I’m likely the only ZF7 in existence