4EAT AUTO Transmission Compatibility Guide

[frood]

Yeah... wouldn't it be nice? So let's collect the data here!

I've been through a lot of suggenstions (Legacy777 and cipher earned a ton of thanks) but have never really known if THIS would fit THAT. It seems that the 4EAT transmission is essentially just refined from time to time, and never really completely redesigned (save the 1998-1999 revamp) in a way that prevents a later model from working on an earlier one.

What I want is for people who have swapped 4EAT's successfully to indicate the:

-----------------------
A)
-Receiving vehicle model (duh legacy)
-Year
-Engine
-Front/rear diff ratio

B)
-Donor vehicle Model (impreza, legacy, svx, etc)
-Year
-Engine
-front/rear diff ratio

C)
PECULIARITIES during install. TCU not compatible, need to replace the rear diff and axles, etc...

D)
How it worked after completion.
-----------------------

THEN we'll start to see some more options open up methinks! I'd MUCH rather have a low-milage 2000 4EAT IF it would work with just a diff swap. Let's face it, low-milage good-condition 4EAT's are getting kind of scarce, and I don't want to replace my beater tranny with ANOTHER 10,000 mile less beater tranny.

BASIC Guidelines and info I've gleaned...

EARLY vs LATE (pre through MY1998 vs MY1999 on)
---CASES
See last page of the following article to see the difference:
http://www.endwrench.com/pdf/drivetrain ... ransOp.pdf

EARLY cases used a 2-4 band and thus had a smooth middle portion to the case. LATE trannies, MY1999+, used a splined middle portion to accomodate a new 2-4 CLUTCH.

---BOLT PATTERN
EARLY case has 4 Bolts and 2 studs
LATE cases have more (8 total holes I count)
BUT it appears that the new locations are backward compatible; It looks like Subaru just added some more bolting points.
QUESTION - Has anyone actually compared if they'll mate up or not?

---TRANSMISSION FILTER
LATE cases have an external "oil filter style" transmission filter.

---OBD I vs OBD II
There -might- be an issue with the introduction of OBD II
QUESTION - Can a vehicle with OBD I use an OBD II transmission?
SUSPICION - Seems that OBD is really just for engine emissions, and it is uliekely that any of the controls necessary for "less polluting" operation be incorporated into the tranny (I'd think the TCU would take care of that).

---EARLY TCU vs LATE ECU
Are there any important differences that would not allow a late transmission to be hooked up to an early ECU? Is this the 'catch' we may run into with the "Band vs clutch" change or can they be controlled by the same signal?

---CONNECTORS
Are the 2 connectors different between the EARLY and LATE transmnissions? Someone must know this or have access to trannies to check them out.

---TORQUE CONVERTERS
I noticed that some of the 'nubs' (bit sticking out at center) on the torque converters had a cylindrical profile vs some having a little 'neck' toward the torque converter itself making the nub look more like a ball. Does this make a difference?

---Pre-1996 Impreza trannies probably fit...
It seems that only 2.2L Impreza AWD's got the 4EAT automatic, not the 1.8 (or whatever) model. This fact can help you on the Hollander interchange when looking up parts:

http://www.car-part.com/

---INTERNAL BIT DIFFERENCES
It seems that over the years, this year got a revamped oil seal, that year got a refinement of the band design, but nothing that made it incompatible with earlier/later years. In fact, many of the improvements that went in to 'this or that' year were also released as service bulletins later on, and -could- have been performed as a repair. In short, new and upgraded tranny parts were backward compatible.

FROOD'S RULE OF THUMB
A - If your recipient and donor cases look externally the same
B - If they both had a 2.2L engine

THEN the trannies are most likely compatible...

BUT the differentials may not be the same You must verify the ratios match OR swap out the rear diff too (probably easier than swapping the front diff out).

Alrighty, I'm done. PLEASE feel free to correct me but not with a line that starts with "I think". Be sure. Back it up.

Thanks all...
Chris, Pittsburgh, PA

[tris91ricer]

All EJ engines fit EJ trannies, auto or standard.
Just stick to 90-94, match the gears/ratio, and you shouldn't have too much of a problem. I'm confused about what you're trying to achieve here, with this guide idea..

[frood]

Yes, but then you have a 90-94 tranny, before the numerous improvements. I want to see which trannies newer than 1994 will fit as well.

Rather than stick a 1992 tranny with 110K on it, I want to see if the 1997 transmission with 57K on it will work, or the 2001 with 34K on it... etc. I'm thinkin' newer here. Cipher did it with a 1995 (or was it a 1996) impreza 2.2 AWD tranny.

I just thought it would be handy. I saw a lot of posts about it over time while I was researching... but not a lot of information in one place. Just trying to be helpful. =)

[tris91ricer]

Duly Noted. I don't have much more to contribute, but I understand what you're trying to do...

[All_talk]

I am currently in the middle of an auto tranny swap, I am also swapping the front diff. So far I have found a few issues with swapping the internal parts but it looks like it will all go back together.

Donor: 1997 Impreza 2.2 AWD
Receiver: 1992 Legacy SS

Notes so far:

Electrical connectors are the same (assuming the pin out is the same).

Keep the Torque Converter with the respective trans, the center input shafts are different on the TC end, the ’97 has a bearing journal on the end, (my ’92 TC wouldn’t fit, but I was able to swap the whole shaft).

The pinion shafts are different, the bearing mounting on the gear end is different but fits the case the same. The splined end is different as well and requires you keep the counter gear that came on it. And be very careful not to loose the spacer that goes on the early (’92) pinion shaft behind the counter gear, I had to go fishing inside the old case when things didn’t come out right.

I’ve been taking pictures along the way and will start a trans/diff swap thread with my pics and notes when I’m done (or post in this one?)

Gary

[TomK]

Hello, this is my first post but I've been browsing this site for two years now since I got my 94 legacy turbo wagon. My tranny is not in great shape but I found a 1998 Outback tranny. Are the 2.5 trannys compatible with the 2.2 turbo (besides changing the diffs).
Thanks

[azn2nr]

yes. all trans, engines and the such will bolt up. your only quest is to find trannys with matching rear diffs.

i have come to the realization that ej motors are more like legos than houduhs are.

[free5ty1e]

Legos rule.

[Legacy777]

The main thing you need to worry about with swapping newer trannies in is the electronics. Other then that, the mechanical fitment shouldn't be an issue.

[TomK]

So to a 94 2.2 turbo, I could attach
- 91 to 94 turbo automatic
- 95 to 98 2.5 automatic

I ruled out the N/A 2.2 tranny because I don't know if it can handle the extra power.

[Legacy777]

I'm sure the na 2.2 can handle the power just fine. If you mod the turbo a bunch, it might be questionable.

Big thing to do regardless is put a tranny cooler and syn fluid in.

[tris91ricer]

Really, the coolers are THAT important? I was told its unnecessary.. However, that was by non-subaru baddies.
I need to find the tranny cooler writeup, too...

[Legacy777]

heat is the killer in an automatic transmission. Stock cooling is adequate, but not great. If you drive agressively, you need a cooler.

[azn2nr]

Really, the coolers are THAT important? I was told its unnecessary.. However, that was by non-subaru baddies.
I need to find the tranny cooler writeup, too...

do a search on nasioc in the trans forum under user name no_coast_punk

[All_talk]

I posted about my front diff swap here:

http://bbs.legacycentral.org/viewtopic.php?t=21482

Just in case anybody cares.

Gary