ELI5: 4WD Auto vs 4WD HI

[MattH89]

Not afraid to admit I'm mechanically illiterate and ask the dumb question.

Since the RHO is 4WD only, what is the difference between auto and hi? On previous vehicles when I needed 4WD I would choose 4HI, so what is auto doing in our case?

 

[Steadi]

Not afraid to admit I'm mechanically illiterate and ask the dumb question.

Since the RHO is 4WD only, what is the difference between auto and hi? On previous vehicles when I needed 4WD I would choose 4HI, so what is auto doing in our case?

4 auto is allowing the onboard computers to decide how much torque to send to the front and rear wheels. One of the engineers in @testerdahl video broke it down. You’ll get the most amount of power sent to the rear wheels in Baja mode. I believe it was a 75 percent bias to the rear.

4hi will lock the transfer case to operate an even torque split all the time, no matter what.

 

[RHOfan]

4 auto is allowing the onboard computers to decide how much torque to send to the front and rear wheels. One of the engineers in @testerdahl video broke it down. You’ll get the most amount of power sent to the rear wheels in Baja mode. I believe it was a 75 percent bias to the rear.

4hi will lock the transfer case to operate an even torque split all the time, no matter what.

That video discussion got quite convoluted…the creator mixed his questions between how 4WD Auto works on most pickups (including Ram’s that are not Full Time 4WD) and how 4WD Auto works in the RHO/TRX. So, people got confused, including the video’s creator.

When in 4WD Auto, RHO behaves like an AWD vehicle with a static torque split that is dependent on drive mode. Yes, Baja is the most “rear biased” torque split that is fixed at 25/75 front to rear. In Auto, it’s a fixed 40/60 front to rear split.

Now, in most 4WD pickups with a 4WD Auto function, the torque split is constantly variable based on traction conditions. This is ideal for optimal handling, but requires a transfer case with a 2WD Hi function. This was ruled out by Ram engineers on TRX due to the Hellcat’s power output & inadequate weight over the rear tires. A safety thing.

As for use cases on the RHO’s Full-Time 4WD system, if there is any chance any of the tires getting traction, leave it in 4WD Auto to avoid drivetrain binding. If you are in deep snow, mud or sand, 4WD Hi or Low is appropriate. Or, just select the appropriate drive mode while in 4WD Auto, and the dash display will tell you which driveline selection to make. Easy peasy.

 

[testerdahl]

That video discussion got quite convoluted…the creator mixed his questions between how 4WD Auto works on most pickups (including Ram’s that are not Full Time 4WD) and how 4WD Auto works in the RHO/TRX. So, people got confused, including the video’s creator.

When in 4WD Auto, RHO behaves like an AWD vehicle with a static torque split that is dependent on drive mode. Yes, Baja is the most “rear biased” torque split that is fixed at 25/75 front to rear. In Auto, it’s a fixed 40/60 front to rear split.

Now, in most 4WD pickups with a 4WD Auto function, the torque split is constantly variable based on traction conditions. This is ideal for optimal handling, but requires a transfer case with a 2WD Hi function. This was ruled out by Ram engineers on TRX due to the Hellcat’s power output & inadequate weight over the rear tires. A safety thing.

As for use cases on the RHO’s Full-Time 4WD system, if there is any chance any of the tires getting traction, leave it in 4WD Auto to avoid drivetrain binding. If you are in deep snow, mud or sand, 4WD Hi or Low is appropriate. Or, just select the appropriate drive mode while in 4WD Auto, and the dash display will tell you which driveline selection to make. Easy peasy.

I got confused? Hmm...

 

[RHOfan]

I got confused? Hmm...

No offense intended…it’s just how the discussion with the engineer naturally progressed. Based on the comments, many people came away with a misunderstanding of how the RHO transfer case works. As you said, further commentary/clarification would just make it worse.