Another gear ratio ?

[Cobr96]

Okay, here it goes, I understand gear ratios and how they affect rpms, but I have a 2020 1500 , 275 55 20s, 4x4 off road with 3.21s, I pulled my travel trailer , about 6500lbs, the truck pulls it fine, but with a 17mph head wind it won't come out of 5th gear, and the rpms are running 3k at 65 mph. And it wants to down shift on hills to 4k. Now if I swap to 3.9s will the truck have a little power to get it to shift into 6th gear so the rpms will drop? If I'm on flat road with no strong wind it will shift to 6th and go down to 2100 rpms. I just want to go into a higher gear I guess and want to know if the 3.92 will get it there.

Thanks

 

[silver billet]

No it won't. Your truck won't upshift because it can't make enough power at the lower rpms. So any gear, from any transmission + rear end combo that puts your engine back into the same RPM at that speed, will have the same "problem".

The 3.92 just gets you started easier. Once you're moving down the road:
3.21 in 6th = 3.92 in 7th
3.21 in 5th = 3.92 in 6th

etc.

So yes your numerical gear will change, but you won't have more power at that speed. If your truck is currently running in 5th at that speed, switching to a 3.92 will just make it run at 6th in that speed, but the actual gear ratio and RPMs will be the same.

Numerical gear is irrelevant. RPMs will be the same for both trucks (within a small range of difference, they are not 100% identical matches, but they are very very close).

 

[Rau]

Okay, here it goes, I understand gear ratios and how they affect rpms, but I have a 2020 1500 , 275 55 20s, 4x4 off road with 3.21s, I pulled my travel trailer , about 6500lbs, the truck pulls it fine, but with a 17mph head wind it won't come out of 5th gear, and the rpms are running 3k at 65 mph. And it wants to down shift on hills to 4k. Now if I swap to 3.9s will the truck have a little power to get it to shift into 6th gear so the rpms will drop? If I'm on flat road with no strong wind it will shift to 6th and go down to 2100 rpms. I just want to go into a higher gear I guess and want to know if the 3.92 will get it there.

Thanks

The wind and aero dynamics are bigger contributors to that than the weight of the trailer in my opinion. I have 7800 lbs trailer and my truck can pull even in 7th gear if I stay behind semi truck where as you mentioned against head wind it won’t go out of 5th.


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[Scram1500]

3,000 to 4,000 rpm all day long is fine for a Hemi, nothing to worry about