Kerrieberry

Hello
I’m new to this site.
We bought a 2021 Winnebago intent 29l October, we loved it but didn’t like the noise and wanted more space. 3 weeks ago, we purchased a 2022 Winnebago forza 34t.
Question, the gas rv slows down to about 50 mph going uphill.
The diesel rv slows down about 30 mph going up the same hill.
Shouldn’t a diesel go up the hill better then the gas rv?
Do I have to manually change gears.
Any help with this, would be appreciated....