4EAT AUTO Transmission Compatibility Guide
Posted: Tue May 03, 2005 6:56 pm
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
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