Getting ready to put a 4EAT from 1991 SS into a 1997 Legacy

[Boostedballs]

I am going to put the turbo trans into the wife's GT. I know I need to swap the rear diff also so I will have a 3.9 front and rear. Now it is stock at 4.11.

Other than just swaping the parts over, is there anything else I need to plan for? The wife will only give me the car for 2 days. She won't drive my SS in the meantime because it's too "obnoxious".

Will I need to swap the TCU over as well?

Will the plugs plug right in?

what else???

[cj91legss]

i think you will

[Legacy777]

You need to check and see whether the 97 has the phase 1 or 2 transmission. The phase 2 transmission has a different plug for one of the transmission plugs. If it is different, swapping is going to be much more of a pain.

As for swapping TCU's, I don't know if you will be able to due to the plugs most likely being different.

I would highly suggest you check out the transmission plugs and the TCU plugs before tearing into this. Last thing you want to do is have the wife's car apart and find out it's not going to work.

[Boostedballs]

Well, the 97 Legacy GT has squareish connectors with slightly rounded corners as does the 91 SS transmission. I think I might be all set.

I did read somewhere that the Legacy changed it's transmission wiring for the 97 1/2 model year. I guess I have the earlier one...

[Legacy777]

Looks like you lucked out

As for the TCU, I'm not sure. You may be able to use the one in the 97. I do know there were a few additional items in the newer transmissions, even the phase 1's. So that's only real issue I see about using the 97 TCU.

[ciper]

Why are you doing this? The car will feel slow.

I searched long and hard to get a 4.44 final drive trans because 4.11 wasnt enough. 3.9 would kill me!

[entirelyturbo]

Better highway mileage, perhaps?

[jdmellor28]

i would not do this if i were you !

i pulled a 1991 4eat out of my dads turbo legacy because the higher gears were stripped out !

it only had 80k miles on it and only had 1st and 2nd gear !

from what i read the old 4eats are weak , but 95 + are bomb proof.

my dads 91 legacy turbo now has a 95 legacy 4eat in it , we had to swap flywheel plates ( or whatever you call that ) TCU stayed the same. to be honest i dont even think i looked to see what the 95 legacy had in it as far as rear gear raito ?

but it drives great

[Boostedballs]

This is the wife's car. She doesn't need the hard launch like I do. She will be turning a few less RPMs on the freeway though, and that's a good thing. We got 29.7mpg on a recent road trip, maybe we can break 30???

She will be getting VLSD with the swap, and that's a good thing too.

I'll be using her 4.11 transmission in my sandrail with the EJ22T. That should be a trip!

[Boostedballs]

from what i read the old 4eats are weak , but 95 + are bomb proof.

I heard the turbo transmissions are bullet proof.

[jdmellor28]

ha ... my dads sure wasnt .. do what u will , im just here to put a word in on things .

[wtdash]

I recommend doing some research over on Ultimatesubaru.org/forum. Check this POST. I followed up w/him last year and here's his response:

Quote:
Originally Posted by wtdash
Hello,
Back in '06 you swapped a '95 4EAT into a '90 HERE. You stated the initial problems w/torque bind were due to a bad TCM (TCU).

Which year's TCM did you replace to get it to work?

Did/does it still work?

Thanks for your time,
Td

After I replaced the TCM it made the car 2wd. Thats why my torque bind issues went away. So I swapped the old computer back in and it was still stuck in 2wd. It stayed like that for a couple of years until I sold it. I never found the true problem.

Jeremy

Even though the connectors may hook up, I don't think they are wired the same.


Also, what I continually read is that the 4EAT, regardless of age, is strong, but must be kept cool. Heat kills 'em quick.

Good luck.

[ciper]

All the phase 1 EJ 4eats are essentially the same when it comes to how much power they handle. The only significant difference is in the final drive,,, which is why the SVX killed transmissions with its ridiculous 3.5 final drive. BTW the SVX has a "turbo" transmission in it

Usually 90-94 torque bind is grooves on the "basket" for the clutches which can be fixed by taking the edge off.
95~early 97 torque bind is from a shaft wearing through a normally nonreplacable item causing pressure to escape.
97-98 fixed the problems.

"NA" transmissions can supposedly be converted to "Turbo" spec, the big difference being additional clutches.

[Boostedballs]

It sounds like I should first try to swap in a different TCU and see what it does. She gets the 16 blinking lights upon first startup. The FWD fuse does nothing. It shifts very nice and firm otherwise. I wish my SS shifted like that.

Well, sometimes it seems to stay in a higher gear when I want to speed up from a near stop. It feels like the engine has all of timing pulled from it.

I might risk just installing the 97 TCU into my 91 SS to see what happens.

[ciper]

I dont think the 97 TCU will work because they use opposite signals from the throttle position sensor.

[Lunatech]

95~early 97 torque bind is from a shaft wearing through a normally nonreplacable item causing pressure to escape.


"NA" transmissions can supposedly be converted to "Turbo" spec, the big difference being additional clutches.

Anybody know what exactly the nonreplacable item is, and could one be made as tough as a turbo by using additional clutches? If so where would be the best place to get them?

[Boostedballs]

I dont think the 97 TCU will work because they use opposite signals from the throttle position sensor.

Do you mean it will NOT work?

[ciper]

I mean that the 90-94 has 5 volts for idle and low volts for WOT vs the 95+ using low voltage for idle and 5 volts for WOT

So yes, I don't think will work unless you had a matching ECU

[Boostedballs]

UPDATE-

I checked that the TCU for the 91 and the 97 are indeed different. They are different sizes and don't mount the same.

The car drives mostly in-town so I opted to keep the 4.11 stock gears. I pulled a tail seaction and clutch shaft from a wrecked 98 impreza. I ohmed out the solenoid and it checked out around 38ohms if I remember right. $42 out the door with a discount! They charged me for a transfer case.

After pulling the tail section on the 97 GT, I was glad I took the shaft from the 98. The 97 GT had some serious gouges in it!

All I needed to buy was some trans fluid, $5 exhaust gasket and $11 exhaust doughnut and a $5 gasket for the tail section. The tail section came with nice tranny mounts compared to the separated ones on the GT. Better clutches, working solenoid and good mounts for $42; tripple score!

What sucked about the job:
-Had to cut all of the exhaust bolts off,
-Tranny leaked out the back overnight,
-Getting the clutch pack lined up properly with the car only on ramps, should have been at least 2' off the deck. I did this one-handed, never again!

Also, There is a ATF line inside the tail section that is sort of pressed into the casing. This line was loose so I flattened out the sloppy sheetmetal clamp to hold the line tight against the case. Not sure if this needed to be done or not, but I KNOW it would have leaked (more) without doing it.

7 quarts of ATF later- Torque bind is gone! The car glides through tight corners and the wife is very pleased with her new car. I think the rest of the drivetrain is equally happy.
-

[Legacy777]

Good work! Glad to hear you got it resolved.