DIY: 4EAT phase 1 power mode wiring

[TireIron]

This works on the phase 1 4EATs from 90ish to 99ish. I don't know if it works on the phase 2, they may have a sport mode version but I have never looked into them.

So this weekend I took a page out of the SVX mods and wired my 98 Legacy 4EAT to stay in power mode at all times. The electronics on the tranny are the same as the SVX ones so it worked perfectly.

I did my research from these sites and don't take any credit for thinking this up.
http://www.alcyone.org.uk/ssm/powermode.html
http://www.subaru-svx.net/forum/showthread.php?t=39133

It works on the legacy just like the svx, but in 96 (at least in the svx) they removed the power light so you don't have a light on the dash when in power mode. All you have to do is run a wire from pin A4 on the first TCU connector to ground.

This is the connector and the empty spot is pin 4. I didn't unplug my connector to do the mod (not my picture).

My picture of it, wiring harness NOT in the car.


The TCU is mounted just to the left of the steering column, you don't need to remove any of the interior parts. I just looked under the dash, removed the 2 10mm bolts holding the TCU on and then ran a wire from that pin and grounded it to one of the TCU bolts when I bolted it back up. I didn't have a terminal from the connector so I cheaped out and just stripped the wire back and pushed it into the hole then wire tied it to the harness. I will get some pictures tomorrow of how mine looks and post them up.

This is where you look under.


Here's the TCU bolted to the brake pedal bracket and you can see the blue wire I ran and grounded to the mounting bolt.


The wiring harnesses are on the left side of the TCU. I unbolted the TCU so I could get to them, it's the top connector. You can see where I wire tied it to the harness to keep it from moving.

[green97gt]

and in essence this just makes the shift hard and late all the time? or?

[TireIron]

not at all. This makes the auto stop hunting for gears and constantly trying to be in the highest gear it can. It makes a world of difference to how the car feels. It will definitly hold gears longer but it will only push them as long as you push the pedal. If you're easy on the pedal then it feels normal. The JDM SVX actually had a button on the console to put it into power mode, they just removed it for the USDM version so it is a feature that was originally built into the cars, not like the resistor to lock the center diff mod.

You could also wire in a switch to this instead of hard wiring it to ground so you can switch it on and off. I figured I would never want it off, and if I do it's easy enough to either snip or unplug the wire. So far I've done about 500 miles on it (yes, that much since saturday, I did 250 today alone) and it is wonderful. The car is there when you use it, it doesn't lag and hunt anymore.

[green97gt]

yerah, my first thought was it needed a switch.

i wonder if it is at all harmful to the trans to be ran this way constantly...i would spose not if they put a button for it on some cars...

i remember in our SVX that power light would come on....sometimes... when driving spiritedly, and other times it would not.

this for sure looks like a better option than fiddling with the line resistor

[TireIron]

Yea, I'll get some pictures tomorrow so you can really see just how easy it is to get to. It is definitely worth trying if you don't like the slushbox feel to these things. And it is probably better for the transmission because it is not hunting for what gear it should be in and slipping the gears to make it shift as soft. Harder shifting is better on the life of the transmisson (it's not jarringly hard or anything, just comfortably firm). When the tranny shifts soft and comfy like it is actually slipping the bands on 2 gears at the same time as it goes from one to the other, slipping the bands causes heat and wear on them and eats away at the life of the tranny.


You could be trick and find a JDM power mode switch somewhere and wire that in hehehe.

[Grafton]

you you take a video of the tach to show the difference in shift points?

[Grafton]

Hopefully this works with a 99 obs the 4eat in that thing drives me nuts

[httrdd]

^ + 1

[TireIron]

The shift point change depends on how much pedal but I will try and get some video of it at some point. Do some research to see what the 99OBS uses for a 4EAT and what it has for a TCU. I know my friends ex-gf had an outback sport and it was horrible but it had sport mode and as long as you kept it in sport mode it drove great, probably the same concept. I forget what year hers was though.

[TireIron]

Updated with pics, will still try and get the video.

[Huffer]

Great idea, never heard of it! If I still had an auto this would have been great! Snappier shifts are much better for an auto - slow shifts and gear hunting result in heat, which is the biggest killer of the 4EATs.

[httrdd]

Suscribed!

[evolegacy]

if this is as good as it sounds I might do this with my 4EAT, can't stand when it searches for the highest gear, gets annoying :smt012

what gauge wire did you use?

[TireIron]

it doesnt carry any current so even 18 is fine, i think that happens to be 16... I had it lying around from a coupe of amp install kits (the remote turn on wire they give) i like it because the blue really stands out.

[evolegacy]

ok, next Q i guess would have to be since you didnt have a terminal for the connector, how secure is the wire in that spot?

[TireIron]

with the size wire I used its a pretty tight fit and then zip tieing it where I did keeps it in place. Next time I get by the junkyard I'll probly strip a few terminals out of a connector and put on in there. Just make sure none of the strands of wire get into a terminal next to it.

[legacy22]

Just did it was a bitch with the auto start box ziptied to the wires going to the TCU but i got it! i just notice my car has to at its running temp before it will shifft into overdrive! is that normal? Definitly can tell its not slipping between gears at all but like you said its not hard just firm! i like now i just hope my tranny dont blow up lol

[TireIron]

The not shifting to OD until warm is part of subarus programming. The tranny shouldnt go into OD until warm, it's bad for it. Thats why if you live in a cold climate you should never eliminate the tranny cooler in your radiator because it can keep it from reaching operating temp.

[legacy22]

nice i figured it was supposed to be that way. I def. like the way it shifts now! For me it almost seems smoother!

[Matty2Hotty]

This work with my 01 lgt BE? I dont have no power mode switch or anything for my auto.

[Stang70Fastback]

Would this work on a 98 Outback? I assume it's all the same electronics?

[legacy98gt]

im wiring mine up with a switch right now i hope it works, did it change your mpg any?

[TireIron]

I think it may have given me like .5-1 MPG MORE because it is staying in the torque band more now.

Yes it should work with your 98.

The '01 has a phase 2 4EAT (started with the 99 model year) and I don't know enough about the phase 2 to know if this will work. I know they changed a lot about them when they switched to the phase 2 including adding a bunch more shift maps to the TCU. It may still have the ability to work, but I have no idea.

[Stang70Fastback]

Sweet. I had a look under the dash and my problem is the keyless entry module is zip tied and attached directly in front of the TCU, so I can't really get to it at all. I don't want to start taking things apart to get to it, because who knows how it all works. Maybe I'll bring it to a mechanic and ask them to help me out since they could likey so it real quick. I'll get around to it one of these days as I'd like to try this out before my car kicks the bucket, lol.

[TireIron]

Yea, my '97 had the keyless module right there. It's only ziptied there, so get some zip ties the right size, cut the ones there, move the module out of the way, do the mod, then zip tie it back up...

[legacy98gt]

i did it but i cant really tell a difference, maybe it shifts a little later but im not sure if its just in my head, i wonder if i put the wire in far enough, i i think i did. is there a way i can be sure its working?

[evolegacy]

Sweet. I had a look under the dash and my problem is the keyless entry module is zip tied and attached directly in front of the TCU, so I can't really get to it at all. I don't want to start taking things apart to get to it, because who knows how it all works. Maybe I'll bring it to a mechanic and ask them to help me out since they could likey so it real quick. I'll get around to it one of these days as I'd like to try this out before my car kicks the bucket, lol.

Dont disconnect the module, just cut the ties from it and move it to the side someplace. I disconnected mine while doin this and lost power to the power lock on the driverside door, annoying so I popped the unit back in.

As for the wire, I didnt notice a difference so I assume I screwed up, Im just pushing it into the connector or am I pushing it all the way thru so the wires are coming out the other side?

[TireIron]

It needs to go in far enough to make contact with the pin on the TCU. If you've been annoyed with how the 4EAT shifts then you will really notice a difference when first driving it.

The older models (possibly '95 and older?) should have a power indicator light on the dash that lights up green and says "power", but the newer ones don't, I think they removed it when OBD 2 came along.

I stripped my wire back at least a 1/2 inch and then pushed it in as far as it would go (the connector was still plugged in). It went in easy for a little ways and then had a little resistance as it went the rest of the way in. I'm figuring this was where it was pressing in with the pin on the TCU. Doing it with the connector connected it cant really go in too far because it will bottom out on the TCU, as long as it doesn't start to press out sideways and connect the other pins, but you would really have to force it in there to make it go that far. And if you are worried about if it's far enough, just go strip a terminal out of a connector on a junk car and insert the terminal and use the wire connected to the terminal. Then you know it will be in far enough.

[legacy98gt]

i stripped it about 1/4 inch and pushed it in until it got hard, should i stripe it more or try to push it in more or both?

[Wiscon_Mark]

Thread moved to DIY section. I will contact the OP about renewing broken image links.