what normally goes wrong on turbo 4EAT

[bry]

I often find legacy turbo and svx cars with blown transmissions. What is the difference between turbo legacy and svx 4EAT, and are there any suitable and cost effective substitutes. What is the typical cause and effect when these transmissions fail. (sorry, no question mark on this computer)....

[Legacy777]

One of the big issues is decreased line pressure, which causes the clutches to slip more and can accelerate their wear.

The turbo Legacy & SVX transmissions are or should be nearly identical.

[bry]

quote per "whitelegacyguy" - "the turbo transmissions are built to a higher spec from the factory. there is one more clutch disk in the forward clutch(gears 1,2,3,4) the high clutch (gears 3,4) and the 2-4 brake band servo piston has a lager apply area (same band). also the transfer clutch has 1 more clutch disk (AWD).
what does all this mean, more torque capacity. of course the non turbo tranny shifts will flare on a turbo motor. your almost doubling the input torque. the tcu's are calibrated differently to match the trans and motor also."

quote per "Legacy777" - "Lower line pressure due to an overall design issue. There is a kit by Transgo that helps alleviate this problem. Line pressure was kept down during shifts to make it a little "softer". However, as a result the clutches sllip more and wear faster."

Here's documentation that came with the TransGo shifter kit.

http://main.experiencetherave.com/subar ... t_Docs.pdf

This means that if you have a turbo or SVX trans that is still working fine, you might want to put in the trans-go kit so it doesn't break down....

According to ECUtune.com, the SVX (and also turbo Legacy) suffers from high clutch slippage (due to inadequate pressure) at cruise causing eventual failure. This is characterized by transmission slippage in 3rd or 4th gear and a delay going into reverse. Of great interest is that often, a complete overhaul is NOT required. The cure is to clean the transmission and valve body, replace high clutch pack and brake band, install the transgo kit to raise overall system pressure, install rebuilt convertor and then flush lines and cooler. These cost effective measures can greatly extend the life of the original transmission.

ECUtune.com also offers a TCU reprogram that will change the shifts to something more along the lines of Subara's own "powermode", except you won't have to punch the throttle to make it work. This will actually increase your fuel mileage and life of the transmission.

[sqc151]

center diff is common to.

[Bdub]

The external filter was/is an option, in addition to the internal filter which IS in all 4EAT Legacy's.

[93forestpearl]

center diff is common to.

The is no center differential in a phase one automatic. There is a multiplate transfer clutch, however. The solenoid controlling pressure to this clutch can go bad causing the car to be locked in 4wd.

[sqc151]

center diff info... http://bbs.legacycentral.org/viewtopic.php?f=7&t=39306

center diff is common to.

The is no center differential in a phase one automatic. There is a multiplate transfer clutch, however. The solenoid controlling pressure to this clutch can go bad causing the car to be locked in 4wd.

[bry]

found basic 4eat info at: http://endwrench.com/main.php?smPID=PHP ... action.php&

and a 4eat rebuild manual at: http://rs340.rapidshare.com/files/12225 ... l_4eat.pdf

basic info on transmission fault diagnosis:

A transmission fault is indicated when the "power" lamp on the instrument panel is illuminated. To display TCU codes:

• warm up engine
• turn ignition switch off
• shift to "D" range
• switch manual button on
• turn ignition switch on
• shift into "3" range
• switch manual button off
• shift into "2" range
• switch manual button on
• shift into "1" range
• switch manual button off
• depress accelerator pedal half-way
• read error code flashed on power lamp

A consistent blinking indicates no fault. TCU and ECU codes may be cleared by removing the #14 fuse located in the lower portion of the instrument panel. Fuse must be removed for at least one minute to ensure the codes are cleared. Take this link for error codes and in-depth discussion: http://www.surrealmirage.com/subaru/trans.html (Courtesy of Legacy777)

Futher diagnosis made by observation of driving and operational characteristics:

• there are 5 or 6 (AWD) solenoids and a temperature sensor in phase 1 4EAT
• shift solenoid 1 or 2 defective = transmission operates in 3rd gear only, 1st only if manual button depressed
• shift solenoid 3 (over-running clutch) defective = engine braking when reducing vehicle speed
• solenoid A (line pressure) defective = line pressure raised to max, causes excessive shift shock
• solenoid B (torque convertor lockup) defective = high rpms in fourth, creats excessive heat
• solenoid C (rear diff transfer clutch) defective = power always transmitted to rear wheels, torque bind in corners
• tps sensor voltage: 4.5V at 0 degress (throttle closed), 0.5V at 90 degress
• line pressure fwd gears: 5.2-5.8 @ idle, 12.2-12.8 @ stall, stall defined as brakes & e-brake applied, wheels chocked, throttle fully applied (no longer than 5 secs and requires 1 min cool down between stall tests.
• stall rpm greater than 2850rpm = low line pressure and or clutch slippage
• delay when shifting to reverse = brake band and or high clutch pack

[bry]

new question - anyone know what is involved in swapping gen 1 legacy 4eat to gen 2 trans. i hear that the later are much more reliable, but i don't know if they are plug and play compatiable with the gen 1 wire harness.

Quote per Ciper - "differences you'll find are mechanical vs electronic speedometer, different final drives, different size torque converter diameters(and matching flex plate), different "internal drive shaft" which turns the torque converter, different mounts and cross member, different length of driveshaft, different shift linkage.

I had to reuse my old shift linkage since the new one was slightly different. I also took the transmission crossmember and made a large hole in the center to allow the use of the new style mount. The new ones have a bolt that goes through the crossmember and has a rubber bushing which prevents excessive upward or side to side movement.

The center differential and transmisison case have been changed throughout phase 1 4eat but you need not worry. All important compatibility issues come from outside the transmission.

I stayed with the original TCU.

There are two flex plate sizes. 2.2NA engines use size A while 2.5NA engines use Size A plus 1/4 inch. As long as you have a complete matching set of Torque converter + flex plate + internal shaft you can use whichever type you want.

The splines on the front differential are the same. Even if for some wacky reason they weren't you can pop them out since they are held in with a spring circlip (kinda like the later rear differentials or the first year of six speed)

The differential doesnt affect the TC type so you could mix and match as needed. Apparently you can even use a phase 2 torque converter on a phase 1 transmission with the right parts.

The driveshaft is a different length because the wheelbase changed. The transmission and center differential and rear differential are all the same sizes.

you will find an extra harness on the transmission and its not something to stress about. This is an "extension cord" for the second 02 sensor '89-'94 legacies don't have "

Any 90-98 phase 1 transmissions are swappable between all Subarus. Try not to swap TCU unless changing gear ratio. TCU has different shift maps for different car weights and gear ratios. According to ECUtune.com, SVX TCU will not work in a Legacy, not sure why.

found some info on a '97 4EAT n/a into a gen 1 turbo legacy: http://bbs.legacycentral.org/viewtopic.php?t=21482

also found some info on early legacy differential gear ratios:

90-94 AWD MT normally aspirated Legacies = 4.11
90-91 AWD AT normally aspirated Legacies = 4.11
91 AWD Turbo VSLD option = 3.90
91-94 AWD MT & AT turbo Legacies = 3.90
92-94 AWD AT normally aspirated Legacies = 3.90
90-94 FWD MT & AT Legacies = 3.70

95-99 2.2 MT Legacies = 3.90
95-99 2.2 AT Legacies = 4.11
95-99 2.5 MT Legacies = 4.11
95-99 2.5 AT Legacies = 4.44

-98 MT Outback = 4.11
-98 AT Outback = 4.44

90-97 AT SVX = 3.54


Here are your donors for a limited slip rear differential:

Impreza:
2000-2001 2.5RS 5MT, 4.111
2000-2001 2.5RS 4EAT, 4.444
2002+ WRX 5MT, 3.545,
2002+ WRX 4EAT, 4.111
2004 WRX STi 6MT, 3.900, mechanical

SVX:
1992-1997 AWD 4EAT, 3.545 final drive, has axle stubs

Legacy:
1991 Turbo, 3.900 final drive, has axle stubs
2000 GT, GT-LTD, Outback-CW, Outback-LTD, Outback-SDN (excluding Outback, Brighton, and L)
2001+ 2.5L (Excluding Brighton and L) 5MT, 4.111
2001+ 2.5L (Excluding Brighton and L) 4EAT, 4.444
2002+ 3.0L (H6) Outback and Outback-SDN 5MT, 4.111
2003+ Baja, see Legacy specifications

Forester
2000-2002 Forester S 5MT, 4.111
2000-2002 Forester S 4EAT, 4.444
2003+ with Disc Brakes 5MT, 4.111
2003+ with Disc Brakes 4EAT, 4.444
2004 XT Turbo 5MT and 4EAT, 4.444


some info on transmissions:

95-98 legacy trans code starts with "TZ102ZA" (phase 1)
In 99 legacy went to a TZ1A2ZJEBA, "TZ1A2ZJ" indicates phase 2 trans.
Late 97 impreza 2.2L AWD went to a phase 2 trans

[ciper]

It would be difficult. The first generation legacy uses a reversed throttle voltage from the later ones. They are not plug and play since the control mechanism inside the transmission was changed. You would probably have to change the TCU, the ECU, the throttle body and the IAC at a minimum.

[bry]

i'm not sure what control mechanism in the transmission you are refering to. do you mean solenoids. there is no logic other than pressurized hydraulic internal to the transmission.

the electrical plugs on the transmission from gen 2 are the same design as gen 1, at least from '95-'98. i do not know if the pins are in the same order, or if these go to the same solenoids. i've been told the solenoids are essentially the same for gen 2. you cannot swap a phase 2 tcu since it would misinterpret the signals sent by the ecu, which are based on tps voltage (reverse voltage to phase 1 as you mentioned).

on the svx forum, a guy is selling late model trans and diffs, and they are said to be swapping directly in without ecu or tps changes. from what i can tell, the svx transmission is the same as a gen 1 turbo legacy except the front diff is 3.54 vs 3.90. the difference between a normal aspiration legacy tranny and turbo tranny is additional friction and reaction discs in the clutch pack. this enables it to handle more torque without slippage.

[Legacy777]

decreased line pressure due to filter clogging or due to pump vane or ring damage. (sorry, no question mark on this computer). am i correct in assuming the turbo transmissions do have an internal filter. what about normally aspirated. i have seen pics of an external canister filter for early legacies, but have never seen one in person.

Lower line pressure due to an overall design issue. There is a kit by Transgo that helps alleviate this problem. Line pressure was kept down during shifts to make it a little "softer". However, as a result the clutches sllip more and wear faster.


There is some additional functionality on the phase 1 95-98 4EAT's. The main plugs are going to be the same, but controlling everything is what's going to be different.

Regarding the TPS voltage being reversed. As long as you use the right TCU for how the TPS is setup, it should be good. I haven't dug into all the wiring differences and if you can swap TCU's or not....but the TPS issue is probably going to be the biggest hurdle.

[ciper]

BRY dammit my mistake. I misread your post as saying phase 2 transmission and not second generation legacy. It is "common knowledge" that all Legacy/Forester/Impreza/SVX transmissions from 89-98 or so are almost the same. They changed internals over the years so the later transmissions are in some ways better. Some differences you'll find are mechanical vs electronic speedometer, different final drives, different size torque converter diameters(and matching flex plate), different "internal drive shaft" which turns the torque converter, different mounts and cross member, different length of driveshaft, different shift linkage.

With that said I am running a 98 outback transmission with 4.44 final drive in my 91 legacy

In 99+ the control mechanism of the transmission changed so you need a phase 2 TCU to go with the phase 2 transmission.

[bry]

yes, the 4.44 is what the guy on the svx forum is selling. so, do tell, how did you make it work and what issues should we be aware of. did you use the gen 2 tcu or stay with gen 1. does a gen 1 flexplate bolt up. i know the torque convertor and front differential driveshaft splines are different, but that shouldn't be a problem if one decides to keep the gen 2 front and rear diff. if one decides maintain original gearing, the front diff can be swapped, but you would have to use the gen 2 convertor, shaft, bearing, etc.

you mentioned the rear diff driveshaft is a different length. is that because it was changed from clutch pack to transfer case. (again, no question mark on this computer)...

do you have a writeup of your swap on this forum. i haven't found it if you do....

appreciate your experience and input!

[bry]

Lower line pressure due to an overall design issue. There is a kit by Transgo that helps alleviate this problem. Line pressure was kept down during shifts to make it a little "softer". However, as a result the clutches sllip more and wear faster.

i see that the oil pump is variable displacment due to eccentric cam. does the trans go kit modify the valve body with springs to increase overall system pressure, or just for certain shifts. i have some experience with auto transmissions, but have only rebuilt GM transmissions, which are way different than the subie.

[ciper]

In case anyone is interested in the differences between a phase 1 and phase 2 4EAT please read this pdf
http://www.endwrench.com/pdf/feb2004pdf/4EATPhase2.pdf

yes, the 4.44 is what the guy on the svx forum is selling. so, do tell, how did you make it work and what issues should we be aware of.

did you use the gen 2 tcu or stay with gen 1.
does a gen 1 flexplate bolt up.

i know the torque convertor and front differential driveshaft splines are different, but that shouldn't be a problem if one decides to keep the gen 2 front and rear diff.

if one decides maintain original gearing, the front diff can be swapped, but you would have to use the gen 2 convertor, shaft, bearing, etc.

you mentioned the rear diff driveshaft is a different length. is that because it was changed from clutch pack to transfer case. (again, no question mark on this computer)...

do you have a writeup of your swap on this forum. i haven't found it if you do....

The biggest issue with the 4.44 is that you will need larger tires or your speedo will be off by about 9.5% while the odometer will be off by about 7%. Acceleration is great but RPM at highways speed might be too high even with the TC locked. You will also need to swap the differential carrier into a newer style diff since 4.44 rear differentials are EXTREMELY rare in the old female axle style. I got one from Japan a long time ago but realize its way easier just to grab one from an outback auto and swap in the old carrier.

I had to reuse my old shift linkage since the new one was slightly different. I also took the transmission crossmember and made a large hole in the center to allow the use of the new style mount. I ripped SOOOOOOO many of the old mounts because they have nothing to limit travel. The new ones have a bolt that goes through the crossmember and has a rubber bushing which prevents excessive upward or side to side movement.

The center differential and transmisison case have been changed (among other things) throughout the range of phase 1 4eat but you don't need to worry. All the important compatibility issues come from outside the transmission.

I stayed with the gen 1 TCU because of the previously mention issue of needing to swap the TCU/ECU/Cruise control/Instrament Cluster/Throttle body issue. I also make EXTENSIVE use of the manual button to control shifts since I like to go full throttle without completely winding out the engine and drawing attention.

From what I can tell there are two flex plate sizes. 2.2NA engines use size A while 2.5NA engines use Size A plus 1/4 inch. As long as you have a complete matching set of Torque converter + flex plate + internal shaft you can use whichever type you want. Right now I am planning to move to the larger size TC/Flexplate with nippled internal shaft but I need to find the larger flex plate.

The splines on the front differential are the same. Even if for some wacky reason they weren't you can pop them out since they are held in with a spring circlip (kinda like the later rear differentials or the first year of six speed)

The differential doesnt affect the TC type so you could mix and match as needed. Apparently you can even use a phase 2 torque converter on a phase 1 transmission with the right parts. I want to try this so I can get the variable vane speed setup like the 02 WRX had.

The driveshaft is a different length because the wheelbase changed. The transmission and center differential and rear differential are all the same sizes.

Here is the closest thing to a writeup I have http://bbs.legacycentral.org/viewtopic.php?f=25&t=42516

Edit: This is only a guess but now that I think about it,,, I bet there are two sizes of torque converter for engine output levels. I bet that under 150HP they use the smaller one (ej16, ej18, ej20na, ej22) while over 150hp they use the larger size (ej25, eg33, ej22t, ej20t)

Oh and you will probably find an extra harness on the transmission and its not something to stress about. This is an "extension cord" for the second 02 sensor our cars don't have

[Legacy777]

i see that the oil pump is variable displacment due to eccentric cam. does the trans go kit modify the valve body with springs to increase overall system pressure, or just for certain shifts. i have some experience with auto transmissions, but have only rebuilt GM transmissions, which are way different than the subie.

There's a few things that get modified in the valve body, I don't recall exactly what gets modified. I think one or two of the passages get blocked off in the plate. It's been a long time since I had it installed.

[Legacy777]

I actually found the kit. It still has the instructions. I could try and scan them so you can see what all it modifies.

The number on the kit is:

"RE4R01A Shift Kit"

[bry]

Ciper, excellent post!!!! That is exactly the information I have been trying to piece together.

Josh, would appreciate it if you could scan the Trans-go instructions so I can tell what is being modified. Will also be good reference material stuck to this thread.

In the meantime, I'm going to try find the link that has discussion of subaru ratios (not just manual trans ratios as shown in the FAQ sticky). I know I've seen it somewhere, but maybe it was on another site. Would like to add it to this thread as well. With this last bit of information, this thread should be a pretty good guideline for 4EAT operation and swap compatibility.

Again, thanks for your help guys!

[Legacy777]

Here's documentation that came with the TransGo shifter kit.

http://main.experiencetherave.com/subar ... t_Docs.pdf

[93forestpearl]

center diff info... http://bbs.legacycentral.org/viewtopic.php?f=7&t=39306

That is for a manual transmission, which is completely different from an automatic.

The differential doesnt affect the TC type so you could mix and match as needed. Apparently you can even use a phase 2 torque converter on a phase 1 transmission with the right parts. I want to try this so I can get the variable vane speed setup like the 02 WRX had.

The input shaft is what needs to match the torque converter. So, to go to a WRX converter, you pop in a WRX input shaft, which plugs right in. WRX converter is a much beefier design, so if you're making enough power, it is worthwhile.


There isn't much of a difference between SS and N/A converters. The transmissions themselves are a bit different, but either can be used to make a built auto.



Anyone trying to get serious with an auto needs to have a phase 1 tranny worked over.

i'm not sure what control mechanism in the transmission you are refering to. do you mean solenoids. there is no logic other than pressurized hydraulic internal to the transmission. as i understand, even a transmission without tcu will shift, although extremely poorly and probably not for long...

Subaru automatics are completely electronically controlled. If you unplug the TCU, the transmission will be stuck in third all the time.


Also, simply swapping a phase 2 TCU to run a phase 2 transmission isn't going to happen. You will have to get into the wiring harness to change things. The phase 2 stuff has many more inputs so it's simply not a plug-in deal.

[sqc151]

so all the 5spds have center diffs and the autos have multiplate clutches??

[93forestpearl]

Yes, the 5 speed manual transmissions have an actual differential. The autos are just a multiplate clutch since the front wheels are directly connected to the transmission output via the transfer gears.

However, the newer stuff, like in a WRX, has an actual differential in the center.


Transer Clutch ("center diff"):

[bry]

Here's documentation that came with the TransGo shifter kit.

http://main.experiencetherave.com/subar ... t_Docs.pdf

Thanks Josh, that is helpful. Lack of pressure does appear to be the failure culprit. By installing this kit which raises pressure across the board, stiffens the accumulators and increases oil drainback to the pan, you have won half the battle. The other half is changing the internal filter every 60k and possibly adding a separate cooler.

I've had pretty good luck with the Trans-go kit on other makes. I like the way "Gil" is all laid back and writes the stuff in layman's terms...

I noticed that in part of the instructions, it says "except Subaru". Is this shift kit the same used in the 1st gen Nissan Pathfinder? I've also read that Ford and Mazda a variety of the 4EAT, called a F-4EAT. Funny thing is, this was used in FWD cars with transversely mounted engines, i.e. escort, probe, etc...

[93forestpearl]

I noticed that in part of the instructions, it says "except Subaru". Is this shift kit the same used in the 1st gen Nissan Pathfinder? I've also read that Ford and Mazda a variety of the 4EAT, called a F-4EAT. Funny thing is, this was used in FWD cars with transversely mounted engines, i.e. escort, probe, etc...

The SS auto trans is a JATCO unit that was used in a few vehicles, like a pickup or two, 300zx, etc.


Along with the reprogramming kit from Trans-Go, a few select things will make the auto hold massive amounts of power.