Jump to content
Ultimate Subaru Message Board
monkeyposeur

Phase II 4EAT swap to Phase I

Recommended Posts

The 4EAT in my 93 Turbo Legacy has 180k. It shifts great and works as it should but I am looking for options in case it shits the bed.

 

I could swap in an NA Phase I Legacy 4EAT, but I want to know what else I could swap in. I am trying to find a JDM TCU so I can run a 20G VTD trans but can't locate a TCU (any help locating one would be awesome!!!).

 

Does anyone have any info how to swap in a phase II 4EAT? I would imagine it would require swapping over the Phase II trans wiring at the very least. I

 

Someone has to have done this, lol.

Share this post


Link to post
Share on other sites

I dunno about the swap, I know it's been messed with those, I've seen threads about it.

 

If you do try and put a phase 2 trans in there, avoid 99-02 as they have issues with delayed engagement with eventual failure. It can be fixed if you wanna drop the valve body and replace seals.

 

Your current trans is actually a pretty reliable box, change the fluid and filter and it should last a long time.

Share this post


Link to post
Share on other sites

Yeah, it's a good tranny. I just like to plan ahead since I want to keep the SS forever. 

 

A few strange issues have occurred with it though. There is a rattling type noise coming from the front of the bellhousing, where the torque converter is located. It goes away at higher rpms though. It's not a loose heat shield either. It isn't causing a problem but I don't like it and have no idea what it is. The other problem is the Duty-C solenoid code was flashing. I dropped the tailhousing and replaced the duty-c with a superseded part from Subaru. The torque bind and flashing went away for about two hours and came back. That pissed me off a little since replacing the duty-c is kind of a big job. I did all the FSM diagnostic procedures which indicated a faulty TCU. I replaced the TCU with another turbo TCU of the same year from a working vehicle and got the same flashing and torque bind. I checked the resistors and transistors of the TCU and they were all within spec. So on a whim I swapped in an NA TCU and the flashing is gone as well as the torque bind. It has a slightly different shift pattern now, but I have the POWER mode wired up and with that it shifts pretty good, and at WOT I can run it up to the redline.

 

I have done multiple drain and fills and the fluid is nice and clean. To replace the filter I would have to drop the transmission pan, and the generally don't clog up so I'm not going to mess with that. There isn't an exernal trans filter on my 4EAT like some later models.

 

I am also trying to source a JDM VTD TCU for an EJ20G Auto trans since I can find low mileage JDM transmissions pretty easily, but the TCU is proving impossible to find.

 

I am also installing a RobTune TCU soon so there will be a bump in hp and like I said, just in case it breaks down the line I want to know what options are available. I would rather just swap in a JDM 5MT but my wife drives the car and loves having an automatic even though she can drive a stick just fine.

Share this post


Link to post
Share on other sites

I would highly advise changing the filter, it doesn't take a lot to reduce oil flow through the filter causing other problems. Dropping the pan really isn't a big deal.

Share this post


Link to post
Share on other sites

OK, If I get some extra time I'll think about dropping the pan. I know it won't be a big deal although some report issues getting the pan to seal. I just replaced the steering rack, tie rod ends, oil pan, power steering lines, duty-c solenoid, did three drain and fills so I'm a bit tired of being underneath the car for a while at least.

 

Most of what I have read on bbslegacycentral says not to bother with replacing the internal filter but I'll definitely keep it in mind.

Share this post


Link to post
Share on other sites

Sealing problems are directly related to people bending the pan lip when removing it, and not getting all the old rtv off both pan and transmission.

 

The problem with the phase 2 tcu swap is that it will be expecting to see signals that phase 1 ecus do not send. I've tried running a 97 and 98 25d ecu in a 99 GT for testing purposes. Both put the tcu into limp mode despite all 3 being "phase 1 ecus".

  • Like 1

Share this post


Link to post
Share on other sites

Internal filters are pointless to replace. It’s just a screen and other than a couple flecks they’re never clogged. If it’s clogged your trans ain’t long for the world anyway and would probably fail with any increase or improvement in fluid flow LOL.

Share this post


Link to post
Share on other sites

Sealing problems are directly related to people bending the pan lip when removing it, and not getting all the old rtv off both pan and transmission.

 

The problem with the phase 2 tcu swap is that it will be expecting to see signals that phase 1 ecus do not send. I've tried running a 97 and 98 25d ecu in a 99 GT for testing purposes. Both put the tcu into limp mode despite all 3 being "phase 1 ecus".

interesting, nice hit. 99 is a phase II trans so the Phase I ECUs somehow accommodate that?

Share this post


Link to post
Share on other sites

Sealing problems are directly related to people bending the pan lip when removing it, and not getting all the old rtv off both pan and transmission.

 

The problem with the phase 2 tcu swap is that it will be expecting to see signals that phase 1 ecus do not send. I've tried running a 97 and 98 25d ecu in a 99 GT for testing purposes. Both put the tcu into limp mode despite all 3 being "phase 1 ecus".

 

I'm confident that if I pulled the pan I could do it right. I've build a few shortblocks and swapped engines and trannies, etc.

 

Thanks for the info. I was wondering the the ecu had to communicate with the tcu or if they were independent. So it seems like the only way to get a phase 2 to work properly would be to do a complete wiring harness merge and engine/tranny swap. I was looking into doing that but I have since decided to go with a RobTune ecu. 

Share this post


Link to post
Share on other sites

If you're on Facebook you may be able to get some help finding the vtd tcu you're looking for from some of the Australian and New Zealand members on the subaru pages. Ben Thurgar has been a good source of parts for many people in the last few years.

Share this post


Link to post
Share on other sites

Cool! I'm not on FB but I'll try and get in touch with that Ben dude! My buddy said he found a guy in Australia that would find me one. Wonder if it's the same guy. Weren't you looking for some 22T pistons a while back on bbs? I have a set that I might toss soon.

Share this post


Link to post
Share on other sites

I was looking for some a while back, I ended up getting two sets and never using them lol. Ben is in NZ, but there are several helpful guys from AUS. Hopefully they'll be able to find the tcu you need.

Share this post


Link to post
Share on other sites

 

 I have a set that I might toss soon.

 

If you plan on keeping your SS w/the EJ22T 'as is' I'd keep those as I've blown @ least one ringland....but maybe it'll be time to upgrade to forged?

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×