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RX Tranny into a 99 Legacy L wagon with a motor swap


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14 replies to this topic

#1 The Korean

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Posted 02 January 2007 - 11:15 PM

Hello all!
So after seeing pictures of a Forester with a ea82 dual range tranny I got to thinking...

What are the complications that I am going to run into if I swap in a RX Tranny into a 99 Legacy L Wagon with a soon to be 2.5 NA motor?

A few questions off the top of my head are:
-I know I need an adapter plate, ea82 flywheel, ea82 clutch, 3.7 rear diff but what else?
-Is there any way to change the gear ratio without binding? Like could I take the RX tranny and swap in my Legacy gears? Im worried about the 3.7 gear ratio...
-Do I need a custom flywheel or does it need to be modified?
-Will I need to change the clutch assembly out?
-How much power will the tranny be able to take?
-Will the front drivetrain need to be modified and if so what will need to be done?

Reasons for doing this:
-Its different and unique
-Very few people have done this... at least to my knowledge
-I will have a 5-speed with a high low gear and a center locking diff control


I think that is all for now!
Thanx
Korean

#2 Numbchux

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Posted 07 January 2007 - 09:45 PM

An RX tranny will need quite a bit of work to be worth swapping in there. the lo range is very meager. simply a 1.2:1 reduction. the only time you really notice the difference is in the already far too low 4th and 5th gears.

the locking center is neat, but the EJ viscous diff works great for everything.

I just spent 4 days with the MNSubaru at the annual Ice Race event. and quickly found out that the locked center really wasn't any different than the viscous center in the EJ cars, except you don't need to unlock them when you get out on the street. AND, you have some traction control on the street. if you try to accelerate hard out of a corner on the street (center diff needs to be unlocked) you'll get unlimited wheelspin on the inside front wheel, and no traction.

and with the EJ22 (which you probably have either that or an EJ25), the extra torque means it's faster to drive in hi-range, and shift less frequently

also, don't let the 3.7 axle ratio fool you, the gears are much shorter, and you'll be running much higher rpm's on the freeway.

don't get me wrong, it's a cool tranny, and I intend to keep using it, but when I get it the way I want it, it'll have taller 1-5 gears, and lower lo range. aswell as a front LSD.


I don't want to discourage you, but I want to be sure you know that this tranny is not all it cracked up to be. ever since I finished my wagon, I've had one complaint. the tranny. I've been very disappointed with it. The tranny was designed for the EA82t. and there's more than a few reasons they changed the design with the new motor.

nobody really knows how strong they are, but they're pretty tough. but almost everyone who upgrades motors, upgrades trannies as well. but I suspect it has very similar strength to an early EJ 5-speed.


BUT, to answer your question, I can only help a bit. This swap is pretty rare. but as you mentioned, you'll need an adapter plate, flywheel, clutch, rear diff, and tranny. the rear diff will bolt right into your car, so no worries there, it's an upgrade anyway. the driveshaft will need to be modified (length is different, though I'm not sure how much, or even which direction). and the linkage will need some work. you're car might also be a hydraulic clutch system, and the RX tranny uses a cable clutch, so you'll need to convert.


some good info on RX tranny gearing, and a good solution:
http://www.ultimates...ead.php?t=68752

#3 baccaruda

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Posted 07 January 2007 - 10:28 PM

Nice job on that.
You've been putting out a lot of really good stuff over the last year or so :headbang:

#4 The Korean

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Posted 07 January 2007 - 11:25 PM

WOW thanx! I'll get back to a reply later, but thanx for a good explanation.

#5 kingbobdole

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Posted 08 January 2007 - 01:40 AM

(not that I dont want to sell my tranny but...) I agree... The rx tranny is kind of a false legend... its nice and all, but the gearing sucks... Thats why I chose the impreza tranny when I put the EJ25 in my Rx.
A thing on Numbchux post I'd like to point out...
The hydro clutch fork will fit the Rx tranny... (my Rx fork fit my impreza tranny just fine) So you'd just need to mount the clutch slave on the tranny somehow.. either welder, or drill and tap or... JB Weld.. :lol: :banana:

#6 Numbchux

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Posted 08 January 2007 - 03:46 AM

(not that I dont want to sell my tranny but...) I agree... The rx tranny is kind of a false legend... its nice and all, but the gearing sucks... Thats why I chose the impreza tranny when I put the EJ25 in my Rx.
A thing on Numbchux post I'd like to point out...
The hydro clutch fork will fit the Rx tranny... (my Rx fork fit my impreza tranny just fine) So you'd just need to mount the clutch slave on the tranny somehow.. either welder, or drill and tap or... JB Weld.. :lol: :banana:


hmmm.....interesting. good to know!

#7 The Korean

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Posted 08 January 2007 - 12:32 PM

So all in all do you think it would be worth it? I mean it is somthing different, haha.

#8 Numbchux

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Posted 08 January 2007 - 01:12 PM

So all in all do you think it would be worth it? I mean it is somthing different, haha.


it depends what you want out of it. and what you do with the car. if you're autoXing and RallyXing, don't. but if it's just a daily driver/toy, and you want it go for it.

but for what I want out of my car, I would say no. it would be worth it in an EA82 car where everything bolts up, and fits perfect. but the amount of work required to get it to fit up to a legacy....I just don't think it's THAT different and cool.


unless...you swap some gears around, drop in an LSD, etc. click my link above for some thoughts on gear ratios to make the RX tranny more than it's legend.

#9 The Korean

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Posted 08 January 2007 - 01:17 PM

it depends what you want out of it. and what you do with the car. if you're autoXing and RallyXing, don't. but if it's just a daily driver/toy, go for it.

but in all reality, I would say no. it would be worth it in an EA82 car where everything bolts up, and fits perfect. but the amount of work required to get it to fit up to a legacy....I just don't think it's THAT different and cool.


unless...you swap some gears around, drop in an LSD, etc. click my link above for some thoughts on gear ratios to make the RX tranny more than it's legend.


The car is used as a daily driver with a hint of spirited mountain driving.

The plan for the car is as follows:
Swap in the EJ25 NA motor
Do light modding including the suspension
Swap in RX Tranny
Add MiniMac CarPC
Add Sound System

I want to do something different including the tranny and I like your idea of dropping in a LSD and stuff like that. I'll be looking into it a little more I suppose.

#10 kingbobdole

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Posted 09 January 2007 - 01:11 AM

Add MacMini CarPC

I sooo need to do this to the 6.... I love my mac mini!:banana:

#11 Numbchux

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Posted 09 January 2007 - 02:58 AM

unless you're accelerating hard out of tight turns, you probably won't notice the open center diff.

it'd definitely be different. but, in stock form, not really an upgrade

#12 Free Range

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Posted 09 January 2007 - 11:53 AM

I'm putting the RX trans into my '91 lego with the 2.5 block/2.2 head frankenmotor. the real reason for me is I want the locked center diff, a slightly lower first gear and awd for the street, I do a lot of irrigation and random ranch work in this rig and with the awd the lego plain sucks offroad, with the locked center I can go out wheeling and keep up with most of the tame rigs in my RX as it is, so into the lego it will go.

#13 Numbchux

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Posted 11 January 2007 - 11:15 PM

I'm putting the RX trans into my '91 lego with the 2.5 block/2.2 head frankenmotor. the real reason for me is I want the locked center diff, a slightly lower first gear and awd for the street, I do a lot of irrigation and random ranch work in this rig and with the awd the lego plain sucks offroad, with the locked center I can go out wheeling and keep up with most of the tame rigs in my RX as it is, so into the lego it will go.


1st gear is the same. your legacy probably has 4.111 gears. 3.7 axle ratio after a 1.96 lo range is comparable to 4.444 axles. the difference is unnoticeable in 1st gear.

and the EJ viscous center is very strong. Austin's imp got high-centered up here in MN about a year ago and he had both front wheels up in the air, but the rears were on the ground. and the center diff still pushed enough power to the rear to cause one of the rear tires to dig a hole. I bet the reason your RX is more capable is the rear LSD, not the lockable center.


like I said, I don't want to discourage people. but I also don't want people to be as disappointed and frustrated as I have been the last 6 months. putting that RX trans in my car was a total pain, and I don't think for a second that it was worth it.

#14 mikeshoup

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Posted 11 January 2007 - 11:39 PM

Now put a 1.5 low range in the RX box, then it would be worth it :headbang:

#15 Numbchux

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Posted 12 January 2007 - 03:53 AM

Now put a 1.5 low range in the RX box, then it would be worth it :headbang:


that's one of my goals for this spring. taller 1-5 gears, lower lo range, and LSD front.




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