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An Engineer's Ultimate Guide To 3.21 VS 3.92 Axle Ratio

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HSKR R/T said:
Or he could just post his GVWR and do some math based on his payload sticker to get his vehicle weight.
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From web site “weigh-safe.com” dated September 28, 2023.
(Begin article quote)

How to Determine Curb Weight​

“For most vehicles, you won’t have to calculate the curb weight on your own. The owner’s manual will usually provide this information, or you may be able to find it on a sticker located within the driver’s door.

However, if you can’t find the curb weight, you can always take the vehicle to a truck stop. These locations have large scales, often used for measuring 18-wheelers, but they can measure any vehicle’s weight. Remove cargo and people from the vehicle to get an accurate weight.

How to Calculate Curb Weight With GVWR​

You can do some math if you still need another option to find the curb weight. Start with the Gross Vehicle Weight Rating (GVWR), your vehicle’s maximum payload capacity. You can find this in the owner’s manual, the driver’s side door sticker, or the manufacturer’s website.

Take the payload capacity and subtract it from the GVWR, giving you the curb weight.“. (End of quoted portion of article.)
 
I have the Rebel with 3.92's. Just out of curiosity, what does everyone with 3.92 turn for RPM at about 75 mph?

Maybe it's just the fact I haven't been on the highway in a while, but, I was doing 75mph today and noticed I was turning 2000 rpm. Seemed a little bit high from what I remember.
 
TheWaterman83 said:
I have the Rebel with 3.92's. Just out of curiosity, what does everyone with 3.92 turn for RPM at about 75 mph?

Maybe it's just the fact I haven't been on the highway in a while, but, I was doing 75mph today and noticed I was turning 2000 rpm. Seemed a little bit high from what I remember.
Click to expand...
Seems about right. I run 1800 rpm at 75 with 3.21’s.
 
TheWaterman83 said:
I have the Rebel with 3.92's. Just out of curiosity, what does everyone with 3.92 turn for RPM at about 75 mph?

Maybe it's just the fact I haven't been on the highway in a while, but, I was doing 75mph today and noticed I was turning 2000 rpm. Seemed a little bit high from what I remember.
Click to expand...
I have a stock 3.21 and 3.92, same size tires 3.21 runs 1750 rpm. 3.92 runs about 400 rpm higher at 2150 rpm.

I have pic for 3.21 I will post, trying to find 3.92 pic (Son drives the 3.92). Your rebel has 33 inch tires that will bring rpm’s down some.IMG_2841.jpeg
 
Ramroo said:
I have a stock 3.21 and 3.92, same size tires 3.21 runs 1750 rpm. 3.92 runs about 400 rpm higher at 2150 rpm.

I have pic for 3.21 I will post, trying to find 3.92 pic (Son drives the 3.92). Your rebel has 33 inch tires that will bring rpm’s down some.
Click to expand...

I'm about 2000rpm at 75 mph with the stock tire size so it seems right.
 
TheWaterman83 said:
I have the Rebel with 3.92's. Just out of curiosity, what does everyone with 3.92 turn for RPM at about 75 mph?

Maybe it's just the fact I haven't been on the highway in a while, but, I was doing 75mph today and noticed I was turning 2000 rpm. Seemed a little bit high from what I remember.
Click to expand...

Sounds about right. The extra overdrive gear in the ZF transmission makes highway speed more practical for the towing axle.
 
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