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Guest Message by DevFuse
 

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Real FULLtime 4EAT??


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15 replies to this topic

#1 Skip

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Posted 10 December 2003 - 06:17 AM

After driving my FT4wd 4EAT in the snow, I feel the 4wd kick in after a small amount of front wheel spin. This is normal behavior as the TCU needs to compare the two VSS (vehicle speed sensors) and react to the difference by sending a signal to the duty solenoid locking the clutch pack for the rear drive.
My question is has anybody investigated putting a switch in so that it acts like a true 4wd ( a center "diff lock" if you will)??
Will the duty solenoid shift into 4wd when recieving a signal, or does it use it's signal to stay in 2wd. (Thus the reason for the 2wd fuse)
I have an spare automatic push button 4wd gear lever, I would like to wire the push button to activate the "diff lock".

Maybe I should take this to the "New Gen" forum?


#2 XSNRG

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Posted 10 December 2003 - 10:02 AM

Yes, me need know too!!!!

#3 Meeky Moose

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Posted 10 December 2003 - 10:06 AM

i don't see why that wouldn't work if indeed it uses an electronic signal to engage it..

#4 TROGDOR!

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Posted 10 December 2003 - 11:46 AM

Skip- the XT6 guys have been wondering about this as well. If they make any progress on it before you do, I'll keep you posted.

#5 jmr052

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Posted 10 December 2003 - 12:16 PM

I thought that there was someone on the board who was doing rallyx in an XT6 and put in a button to make the tranny "lock up" in the 50/50 split.

Jay

#6 MilesFox

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Posted 10 December 2003 - 01:05 PM

who wasit, that guy who can service ujoints in the driveshaft...
he said something about the vacuum controls the 4wd clutches on a regular 3eat.
but i recall somthing about 4eat to lock in the clutches, but i cant remember if it was vacuum or electrical, i think from the new gen forum

i am going to hook up the 4wd button on my 5spd to the diff lock on the xt6 tranny

#7 WJM

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Posted 10 December 2003 - 08:00 PM

auto and manual FT4WD are different...as i recall. Ofcourse, we all know that manuals use a center diff, and power is constantly going to the rear...in the autos, it seems to be the same design as the newer EJ trans...using speed sensors to adjsut the amount of power ot the rear. Duty soienoids are what they are. In the new gen forum, I remember seeing discussions on this. Since i am not familiar on those autos, I wont start to guess....but there are differen sols. that send different power. On the EJs, there one for 50/50, and one for 90/10...and i *think* there is one for 70/30.

Ofcouse, the manuals have a diff lock. The EJs have a viscous coulpling center diff...in simple terms, something like an LSD. Constant 50/50. Where as our EA82 FT4WDs can lock, giving 50/50 no matter what happens.

#8 bushbasher

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Posted 10 December 2003 - 08:47 PM

From my experience with my 4eat it didn't really matter under hardcore bushbashing, as once you do the little slippy lag thing it seems to stay in 4wd afterwards. If I slipped at the beginning then stomped on it again once moving in the mud there would be no second time lag, it would instantly spin all 4. However there would be a time lag if I took it easy to start then hammered it, I would get a lag. Does anybody know when the tcu decides to disengage the center clutch? It wouldn't do it instantly or the 4wd would stutter on gravel hills etc.

Also from one position I had my car in, the front end was up in the air with one wheel in the air, with the car basically standing on the rear wheels. The one front wheel would spin, whereas the rears with the welded diff wouldn't budge. The one wheel in the air could still spin a fair amount, even though you could feel the rears trying to push the car. The tranny and wheel seemed to slip before the rears would move. Even in 50/50 mode the clutch still slips is what I'm trying to say. Oh ya and after trying to get over the obstacle like this for a few minutes, the tranny started to smoke, so I stopped :D

#9 kevinsUBARU

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Posted 10 December 2003 - 09:14 PM

On AWD subies with the automatic, D and 3 have the 90/10 split until wheelspin occurs. When the selector is in 2, 1, and R, the split is 50/50.

On many early legacys/imprezas, there was also a "Manual" button that "locked" the tranny in a certain gear.

Now, Im a little hazy on the details as my 95 Impreza automatic doesn't have one, but my understanding is if you press the button in 2nd, it will not shift out of second (up or down). Maybe someone a little more familiar with this button can chime in.

Kevin

#10 WJM

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Posted 10 December 2003 - 09:27 PM

Ive seen that feature on many early Legacys.

From my experience with a 4EAT AWD...on a 96 OB, EJ25...front and rear seemed to be 50/50 all the time. And one time, i was nose into a ditch, and one front would spin, and one rear would spin. SEVERE angle of attack...so there was no going forward, or backards. I think it about about 45 deg.

There have been a couple times where I've had the RX spin only the front...but on gravel, all four went. Even on slick mud, with the center diff off, the RX felt like 50/50, even tho its got an open center diff.

The OB never felt like it was out of 50/50, even tho its not supposed to do that in 3 and 4.

#11 mudrat79

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Posted 11 December 2003 - 12:15 AM

I curently have a 91 Legacy in my stable with 4EAT and manual button.....I'll investigate it for you guys....:)

I think it acts more as a lock up stall converter in the converter, giving you better power through the gears, but I 'll check it and get back to you all tomorrow nite on the subject......Wife has the car right now....:)

Later, John in Oregon....

#12 GLCraig

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Posted 11 December 2003 - 01:39 AM

this is how the owners manual for my legacy explains the Manual mode switch.

"the manual mode is used for driving in slippery condidtions. In position 3 the transmission holds 3rd (but shifts automatically between 2nd and 3rd during starting or low speed driving). In position 2 the transmission holds 2nd gear."

#13 myossfeece

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Posted 11 December 2003 - 05:47 PM

My RX has occaisionally spun only the front wheel in wet pavement or slick mud, but if you can get the frontwheels to grip and still break em loose with the diff unlocked it handles like a positrack reardrive. really alot of fun once you get the hang of it.

I think the newer than ea series awd uses a limited slip center differential. the wheel sensors are probably for the abs if equipped.

#14 Skip

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Posted 13 December 2003 - 09:43 AM

Thanks for all the replies, guys
Both on topic and off.
My bad, this is an 89 FT4EAT it has no "manual button"
It has a "1st hold" button only
It also has no provision for starting in second gear,
(I think FHI slipped up here as it is a nice feature for snow running, all my other Subaru autos have this feature)
The gear shift pattern is
2,3,D...
When starting in "2" from a stop, it still downshifts into 1st, then upshifts into "2" UNLESS the "1st hold" button is depressed.
Please believe me on this one.
That said I will now look deeper into the bowels of the FSM chapter on the extremely complex FT4EAT.
Does anybody know where the TCU is located on a 1989 GL-10 wagon? My plan is to add some form of visual indicators for the operation of the varrious duty solenoids.


#15 Mykeys Toy

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Posted 13 December 2003 - 11:52 AM

Skip if you are going to do that, you might try L.E.D.s they are small bright and require less power than pretty much any other light. you could probably color coordinate them to indicate which gear or power ratio on a small console.

mike

#16 Skip

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Posted 13 December 2003 - 01:59 PM

Thanks Mike exactly what I was planning on, I have a few LEDs in the bin. I like the high impedence not affecting the operation of the D.S. being watched.
I will need to to know what level of dwell these units get fed.
I will also have to find out if they are negativly signaled.
I was hoping we had someone that knew this, but alas
I guess I'm guessing





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