Making sense of TRAC, Auto LSD, ATRAC, VSC, & Rear Diff lock.

[kurtfriedrich]

Ok, so given that I am off road and things are "interesting" so 4L is appropriate,
1) is there any condition where turning on ATRAC would make things worse? (why not always use it in 4L?)

2) it seems turning on rear lock may give you some more traction, but it seems it makes the FJ harder to control, so, when would it be better than just ATRAC?
- ?
- ?

When will it be worse than just ATRAC
- if you are going to be forced to make a tight turn and going wide means going off a cliff?

- when on steep climb or desent that has a bad camber, locking tends to make the vehicle "walk" to the side, and cause you to get crooked?

- ?

thanks

Kurt

[Kansas Law Dog]

kurtfriedrich previously said:

Ok, so given that I am off road and things are "interesting" so 4L is appropriate,
1) is there any condition where turning on ATRAC would make things worse? (why not always use it in 4L?)

2) it seems turning on rear lock may give you some more traction, but it seems it makes the FJ harder to control, so, when would it be better than just ATRAC?
- ?
- ?

When will it be worse than just ATRAC
- if you are going to be forced to make a tight turn and going wide means going off a cliff?

- when on steep climb or desent that has a bad camber, locking tends to make the vehicle "walk" to the side, and cause you to get crooked?

- ?

thanks

Kurt

One thought I have, is that just engaging the rear locker when running in the sand dunes might be better. ATRAC makes a racket when applying braking action to the slipping wheel. As long as you have momentum in sand, the rear locker should be adequate for traction and enjoyment.

ATRAC is a great technological advancement. Comparing front and rear lockers versus ATRAC, the advantage for traction with maximum torque favors the front and rear lockers. The advantage of ATRAC is better steering control, with a small compromise of traction at maximum torque.

The key when addressing an obstacle where you might get stuck is momentum, and both ATRAC and rear locker are tools to prevent becoming mired in a "no go" scenario.

[aquaholic]

ok. so which wheels spin (get power) when in 4wd hi and 4wd low only. atrac and rear diff locker aside.

[stringmachine]

read your previous post , i posted a reply to it, hope it is what you needed to read about it

[aquaholic]

oops. mistakenly posted that in this thread while i was reading it. i'll go back to my original.

[FreshChip119]

Very helpful, Thank You.

[Fjamming]

This is great video from Toyota that explains how the rear locker works.

Toyota.com : Vehicles : FJ Cruiser : Bulletin

This is video of how Atrac works.

Toyota.com : Vehicles : FJ Cruiser : Bulletin

[TommyBoy]

TJPyles,

You should be able to drive in 4wd at about any speed, but I wouldn't engage it going faster than 50mph. Even then, tolerances are such that you would probably be ok engaging 4wd up to 70mph, but who's driving 70mph if the conditions are bad enough for 4wd?

I also agree with your statement about the A-trac manual listing. The manual sucks. I read it like you did, and I have a degree in journalism. From page 125 to 126, it makes it sound like you engage it in 4 low and it stays operational even when you go 4 high or 2 wheel. It's very confusing, but that's a Toyota owners manual for you.

Thanks for this thread. It cleared alot up for me.

[Alpine_FJ]

A-Trac does not work with RR locking differential "in locked mode" because if it did this is what would happen: If A-Trac applied the brake to one side of the RR end and the RR differential were locked then it would effectively apply braking to both sides and kill torque to both sides of the RR end. Given that you are now dragging the entire "locked up" RR end on low traction terrain the front wheels will not be able to power you through it and you have now been brought to a stop. Please someone correct me if I'm wrong.

[The_big_G]

Thanks for this, very helpful