Handling on ice

[sunny5280]

On a 4EAT lock the front and rear 50/50 by putting it into 1st (or 2nd if you want less torque to the wheels off-idle). Will stay in either 1st or 2nd and power transfer will be very much like the 5MT - very even - front to rear. As soon as you shift into 3rd or Drive, it goes back to 90F/10 rear until slip is detected.

 

Where can I learn more about this split?

[johnegg]

there is nothing to learn.

 

the computer controls the power split.

90 / 10 favoring the front almost all the time.

and 60 / 40, or so, favoring the front when in need,

such as a spinning front wheel,

or when shifted in to !,

or when shifted into 2,

or at WOT, wide open throttle.

 

however, regardless of the ''demand'',

the computer quickly returns to normal,

when conditions return to normal.

 

oh yeah, reverse is always at a ''front=rear'' power split.

[Stevo F]

That's a better setup than the Toyota Sienna AWD van we have. Only has AWD in forward gears- found that out when trying to back out our icy hill and it started going sideways, so we have to back it in if we expect bad weather.

[Kennyfvholla]

On a 4EAT lock the front and rear 50/50 by putting it into 1st (or 2nd if you want less torque to the wheels off-idle). Will stay in either 1st or 2nd and power transfer will be very much like the 5MT - very even - front to rear. As soon as you shift into 3rd or Drive, it goes back to 90F/10 rear until slip is detected.

 

Where can I learn more about this split?

 

there is nothing to learn.

 

the computer controls the power split.

90 / 10 favoring the front almost all the time.

and 60 / 40, or so, favoring the front when in need,

such as a spinning front wheel,

or when shifted in to !,

or when shifted into 2,

or at WOT, wide open throttle.

 

however, regardless of the ''demand'',

the computer quickly returns to normal,

when conditions return to normal.

 

oh yeah, reverse is always at a ''front=rear'' power split.

 

 

Hmmmmmmmmmmmmm

 

As a few of us found out not too long ago, this widely accepted theory of how the power is split isn't entirely correct.

 

Yes, at speed there is a 90/10 split until there is any wheel slippage. This is when power is sent to the rear. Yes, revers is a 50/50 split. Yes, power is split when at WOT.

 

But, no, the gear selector apparently no affect on where power is sent. It is entirely based on speed. No matter what, you start off with a 50/50 split (or whatever the specific split is). As you increase speed, and there is no wheel slippage, power to the rear is lessened if not needed. I do no know any specifics beyond those details at all. I have forgotten them, honestly...

[Wheelbuilder_25]

The 4eat is quite variable, it looks at the tps, abs and God knows what else to adjust its torque split. Somewhere I had found a Subaru whitepaper on this, it is pretty complex. IIRC it tries to reach 90/10 split, but as an example, if you're stomping the gas, it uses the thinking that weight will transfer to the rear, so it shifts more torque there.

Subaru has updated the controls for this at least twice, the older ones had the mentioned fixed split in 1, 2 and reverse (they also had a mysterious button marked hold). The 2nd gen in my old Outback lacked the button, but seemed to behave in a similar fashion. VDC added way more controls to it, and the 4eat for the WRX had even different internals and control.

 

There is quite a difference to how an AWD behaves to any other vehicle. The variance of torque is predictable, but may not be intuitive if you're used to FWD/RWD. They also have more weight in the rear than many FWD cars, again changing their behavior.

 

Best bet - find a safe place to get a feel for it. Push it past its limits, then find out how to stay within them.

[SBT]

All of the 2nd gen 4EATs (except possibly after the April 1999 upgraded versions) had the "lock" capability in 1st and 2nd. And thanks JohnEgg for mentioning reverse as well.

 

Agree with WB_25, take it out and find it's limits, in all the gears, so you know how it will react in a given situation.

[Kennyfvholla]

Yeah, Phase II 4EAT's were a bit different. Idk anything about those so I won't speak for them.

[TexasLegacy2.5GT]

Are the Phase II 4EAT in the second gen99's or the 3rd gen

[Wheelbuilder_25]

IIRC if it's got a filter on the side, its a Phase II. I think they went into the 3rd gen. Cars101.com is pretty accurate on when things changed from model to model.

[johnegg]

phase 2 auto trans started with the 99 outback, GT, and i think legacy L, mid year.

there are a few, a very, very few, 99 obw that have the phase 1 trans (same as the 98 trans).

at least that is what the interchange software at car-part.com thinks.

i have never seen one.

 

the 99 lego L and impreza use the same trans, same ID#, that is a first.

usually they have different part numbers and different trans ID numbers.

 

in 00 the forester got the phase 2 trans.

 

on a slightly related note:

the 99 forester got the phase 2 ej25, sohc.

and the 99 outback, GT still had the ej25d, dohc .

(although the block was a phase 2 with 8 engine to trans bolts.)

 

by 00 all engines and auto trans were phase 2.