ramffml
Senior Member
- Joined
- Jul 12, 2019
- Posts
- 2,869
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- 5,314
- Location
- ramforum
- Ram Year
- 2019
- Engine
- hemi 5.7
Highway cruise mileage on my 3.92 limited is 20-21. The 3.21 will need to shift more since the 8sp has two overdrive gears. The 3.92 just keeps pulling up those hills. The only way to compare is to change the gears in the same truck driving the same course with the same driver over several weeks to account for different wind and traffic conditions. The 3.92 also provides better holdback downhills.
Both trucks have 2 overdrive gears.
The better way to look at this, is:
8th gear in the 3.92 = 7th gear in the 3.21
7th gear in the 3.92 = 6th gear in the 3.21
Whatever the 3.92 does in 8th, it will be 100% identical to the 3.21 in 7th. But the 3.21 has an extra upshift left and so it will drop 400 RPMs at that point.
Naturally if you come up to a grade and both trucks are in 8th, the 3.21 will be 400 rpms lower so it absolutely will downshift to match the 3.92. And then they're equivalent and both trucks might need to downshift again if needed.
The point of overdrive gears is to use them. I like how my truck basically idles through life. Downshifts are smooth and seamless, its not something I even notice if the tunes are on or I'm talking in the cab etc.
So no, the 3.92 will not pull better up hills nor will it provide more holdback. It just means the 3.21 has one extra gear to up/downshift first but: if the RPMs are identical in both trucks, they have identical performance.