6-Speed Driving "Modes"

[greytandy]

My wife has a 1.5-year old manual tranny FJC and I'm still trying to wrap my brain around the functions.

When in normal full-time four-wheel drive, center diff unlocked but VSC kicks in when skiding sensed. What exactly does the VSC do? Transfer power to non-spinning wheel?

When center diff is locked, VSC is still engaged? Why?

When 4Low engaged, VSC is disengaged but you can engage A-Trac. A-Trac sounds like another anti-slip mechanism like VSC. What's the difference?

The owner's manual ain't so clear on a lot of this, except to tell you what drive "mode" is best for which conditions. I'm just really confused as to what's going on in each case.

Is there a good explanation of this somewhere? Thanks.

My FJ40 is so much simpler.

 

[Stinkyfinger]

My wife has a 1.5-year old manual tranny FJC and I'm still trying to wrap my brain around the functions.

When in normal full-time four-wheel drive, center diff unlocked but VSC kicks in when skiding sensed. What exactly does the VSC do? Transfer power to non-spinning wheel?

yes it applies braking to the wheels that are spinnig to force the wheels that are sliding to spin

When center diff is locked, VSC is still engaged? Why?

The vsc still controls each of the wheels to prevent sliding. When you lock the center diff you transfer power 50/50 to the front and rear axle. When its in normal all wheel drive the power can shift back and forth between the axles up to I believe a 60/40 split

When 4Low engaged, VSC is disengaged but you can engage A-Trac. A-Trac sounds like another anti-slip mechanism like VSC. What's the difference?

They are very similar.
Don't quote me on this, but I believe the A-trac only detects excessive wheel spin from side to side on each axle and the VSC only detects a wheel locking up any where on the vehicle then can correct that wheel by applying brake force to any of the other three

The owner's manual ain't so clear on a lot of this, except to tell you what drive "mode" is best for which conditions. I'm just really confused as to what's going on in each case.

Is there a good explanation of this somewhere? Thanks.

My FJ40 is so much simpler.

Thats the nice think about the FJc it does all the thinking for you.

 

[Dirk Diggler]

When center diff is locked, VSC is still engaged? Why?

When the center diff is engaged in 4Hi, the VSC is NOT on! In a manual tranny, the VSC should not work if the center diff is engaged.

 

[greytandy]

When the center diff is engaged in 4Hi, the VSC is NOT on! In a manual tranny, the VSC should not work if the center diff is engaged.

Yeah, I kinda winged that one. I couldn't remember if VSC was enabled with the center diff locked.

 

[WES1977]

A-Trac sounds like another anti-slip mechanism like VSC. What's the difference?



My FJ40 is so much simpler.

I thought VSC is Vehicle stability control which is pretty much side to side traction to help from skidding.

A-trac was for forward and reverse traction

 

[greytandy]

I thought VSC is Vehicle stability control which is pretty much side to side traction to help from skidding.

A-trac was for forward and reverse traction

Well, it seems both A-Trac and VSC apply selective braking to regain control. I'm trying to physically understand what the difference is in mechanical terms.

 

[Niner]

the way I understand the VSC is like a limited slip differential. it drives front and rear based on load. and like a limit slip differential it is limited. What the FJ does is use the brakes to control the front to back and side to side based on wheel speed sensors used by the antilock brakes. when you select H or L it is locking the center differential.

This is not new Jeep had Quadra trac and GM had their fulltime 4X4 that could be locked in High or Low.

 

[96r50]

From Toyota:

"VSC helps ensure stability during cornering - detecting and controlling oversteers or understeers. Wheel Sensors continuously monitor a series of factors including speed, steering angle, yaw rate and deceleration. If the system detects a loss of control, VSC steps in, dictating brake force and moderating throttle until the situation in corrected and the vehicle back under control."

So, VSC keeps you from driving off the road to the left or right.


"FJ boasts TRAC [Toyota's Traction Control System] as standard fare on all models to control wheel spin, especially on slippery surfaces. Sensors continuously monitor the rotational speed of each wheel. If the system detects that one or more wheels are starting to slip, the engine's Computer Control Unit automatically adjusts throttle accordingly while the Brake Actuator directs the braking force to the most appropriate wheel or wheels until traction is restored."

TRAC cuts power and applies brakes to a spinning wheel so you don't slip on ice etc.


"ATRAC works in concert with FJ's 4-Wheel Drive for improved off-road traction, enhanced escape performance in mud and better acceleration on split road surfaces. ATRAC senses when a wheel is about to slip, then actively directs torque to the wheels with the best grip."

Kinda like a locking front diff, but controlled by the computer, and only available in 4WD (hi or low, not sure)

 

[five-by-five]

...My FJ40 is so much simpler.

True, but it prolly doesn't have as many creature comforts as the FJC does!

 

[Jim S.]

Spent the last week in Death Valley towing my Horizion trailer. At speed on the gravel had the VSC activate several times in the turns. I was applying brakes a couple of times and the pedal goes real hard as the computer takes over. We were definitely skidding and the system seems to work. Drove all the faster & tended to depend on it. Quite cool actually. The skid symbol on the dash will illuminate in a skid of long duration.