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Old 05-24-2003, 10:30 PM   #1
SubaruPreza
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Default EJ25 Swap quesions (axles, rear diff)

I am doing an 1994 EJ18 swap to a 2000 EJ25 engine. Does anybody know if i will need the front and rear RS axles for the swap. The engine i am getting comes with the transmission so would i need the rear differential to work with the rs tranny. Any info would help.

thanks
Aaron
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Old 05-24-2003, 11:00 PM   #2
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You are going to need a rear diff with 4.11 final drive. You can get one for about $500. Your current rear diff will not work due to a different final drive ratio. You can have the 4.11 gears swapped into your L rear diff, but why not just spend the little bit of extra cash and upgrade to the 4.11 LSD. With the LSD, you will need 2000+ RS axles. The front axles from the L should be the same, albeit smaller diameter.

-Jon
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Old 05-24-2003, 11:19 PM   #3
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or you could look for a 99 RS rear diff. it is an open 4.11 and you will be able to use your current axels
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Old 05-25-2003, 09:41 PM   #4
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You want the LSD, they are much more fun in the snow . I believe there are two types of rear axles: the open diff axles and the lsd axles. You will need to select which axles you use based upon the diff you select.

-Jon
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Old 05-26-2003, 01:13 PM   #5
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I heard my tranny will bolt right up to the RS engine. so if i didnt even use the RS tranny how long before my tranny will go out and i have to buy a rear diff and axles. or would you just recomend finding a rear diff and axles when i do the whole swap.
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Old 05-26-2003, 01:22 PM   #6
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Yes, it will bolt up just fine. That would also be an option. The strength of either tranny should be about the same, you just get the newer synchos and lower gearing with the RS tranny. There are a couple locals here who are mating an EJ20 to their old EJ18 trannies.

-Jon
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Old 05-26-2003, 06:41 PM   #7
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is there any power lose by going with that option, useing my tranny and rear diff??
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Old 05-26-2003, 07:18 PM   #8
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power no
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Old 05-31-2003, 08:20 PM   #9
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Quote:
you just get the newer synchos and lower gearing with the RS tranny.
You sure on that? I thought the 1.8 had the shortest gearing of the bunch. I've got the 97 with a 1.8, and planned on keeping my tranny, as I'm fairly certain it's got shorter gearing.

Correct me if I'm wrong, but I think I'm right. Can you show me numbers from somewhere?
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Old 05-31-2003, 08:45 PM   #10
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Default question

sorry guys, didnt mean to butt in. im interested in doing this swap during the summer too. however i was thinking most likely just swapping the engine for now and then save up for tranny and rear lsd for later. but what i want to know is what do i need to just be able to hook up the ej25 into my 93 1.8 L (awd) do i have to have a ej25 ecu with wiring harness? for the harness can i use a 2.2? or am i better off just going straight with the ej25 harness and ecu? need some ideas. been searching the forums but havent come across any complete threads. thanks in advance.

kevin
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Old 06-02-2003, 03:40 PM   #11
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Qaveboy, your car is OBDI and the 2.5l are OBDII. This means you will not be able to just plug in the ECU. You will need wiring diagrams of both vehicles and do some heavy duty splicing.

Streetman, the L gear ratios are lower when you consider the smaller diameter wheels as well. At least 1st is lower. The other gears are a little taller as I recall. Do you know if the Brighton and L have the same gears?
Also I just read an article in Grassroots Motorsports that said the RS tranny had a stronger shaft in it to handle more torque. I don't know if that is really an issue as there are a few EJ20s out there with L trannies. I-speed has done at least one. The L/RS tranny seem to suffer from broken 2nd and busted synchros mostly.
If you swap in an ej20 and start doing drag launches, neither the L, RS nor WRX tranny will last long.
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Old 06-02-2003, 06:02 PM   #12
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I thought I saw that the Brighton had shorter gearing, regarless of tire size. And yes, with 14's it's really short. I'll fix that, once I figure out the brake/wheel setup I'm going to use.

Perhaps you'll know this, as I have anyone to answer for sure, as of yet. How hard is it to go from a 1.8 to a 2.5 if you already have OBDII, and a MAF? I've got the 1.8 in 97. And yes, really, it's a 1.8 in a 97. No one seems to believe me, or thinks I'm an idiot. Don't know why. 97 was the first year for all AWD, but they still had the Brighton model.

So anyhow, 1.8, MAF, OBDII. I'm thinking a 99 2.5 would bolt up almost perfectly, wiring and all. Trying to see if I can get away with just a drop in, and replacing an ECU.

This is way off SubaruPreza's original post about axels. If you want to answer on one of my posts, go for it. Someone needs to document this, as apperently, it's never been done.
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Old 06-02-2003, 06:07 PM   #13
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http://forums.nasioc.com/forums/show...00#post3999000

My thread, as to get off of SubaruPreza's. Sorry dude, just passing through.
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Old 06-03-2003, 11:38 AM   #14
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No problem streetman. I got a pair of WRX rear axles i heard these will work with a rear LSD ( i am still looking for a rear LSD also if anyone knows anybody selling one or where i can get one let me know) , but does anyone know if i will need front axles as well.
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Old 06-03-2003, 02:45 PM   #15
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Are they WRX wagon or sedan axles? If they are sedan axles, you will find that they are each 1/2 cm too long.

As far as I can tell, your front axles are just fine. I have an axle spline count thread in the transmission forum with as much axle information as I have been able to find. The only differences that I have found for the front axles are diameter for ANY of the axles (sedan vs wagon included).

-Jon
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Old 06-03-2003, 02:49 PM   #16
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I'm 90% sure the fronts are the same, you should be fine.

The LSD came aorund on the RS in 2000, and 2001. Then in 2002 and 2003, the WRX got it, but not the RS. You are correct, if you use it, you will need the slightly different axels in the rear. To find the LSD, check for those years in junkyards. There's also a diff from turbo legacy that everyone is fond of, but I don't recal which year, or why everyone loves this thing. Maybe it's limited slip as well.

Your tranny will bolt right up, so you really don't need a new diff right now. In fact, don't need one in the future either. The transmission will last as long as you don't abuse it. So far, with only 110HP, you haven't had the power to abuse it. At least that's the way I feel about my 1.8 motor. Helps that the clutch is slipping too. That tranny has had no abuse.

However, you might as well replace the whole thing, when you do the swap, as long as you're wrenching on it anyway. Then, you'll have a complete driveline left over to build something fun with. After debating the Subaru powered recliner or riding mower, I've decided I'm building some sort of on/off road dune buggy looking something with my driveline.

Have fun.
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Old 06-03-2003, 03:24 PM   #17
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The 1991 legacy had a 3.90 lsd in the MT. I don't think it will work with WRX axles.
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Old 06-03-2003, 11:24 PM   #18
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so the WRX axles will not work if i get a rear LSD from a 2000 RS???!!!
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Old 06-03-2003, 11:40 PM   #19
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Reread what he said. 91 Legacy LSD won't work with WRX axels. However, maybe your old axels will work? Check it.

I believe the 00-01 RS, and the 02-03 WRX all used the same LSD.
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Old 06-04-2003, 01:03 AM   #20
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What other types of rear differentials could i use with the 2000 RS tranny. Would i just have to find any rear differential that has a 4:11 gear ratio. I have seen some forester L rear differentials that have the 4:11 ratio. Would that fit? And do i only need new axles if i get a rear differential that has the LSD?
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Old 06-04-2003, 01:24 AM   #21
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Correct on both accounts. You merely need to match the final drive ratio to that of the transmission you are using. If you do get a new diff, LSD's require different axles from the open diffs.

-Jon
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Old 06-04-2003, 02:04 AM   #22
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I have a new pair of WRX rear axles can these only be used with a 2000-2001 RS Rear LSD or any rear differential that has LSD, or can these work on differentials without LSD. If i go with a rear diff. that isnt LSD can i use my stock axles or will i have to get new ones. I am guessing that the Rear LSD's are more expensive than other rear diff's?
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Old 06-04-2003, 12:16 PM   #23
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WRX axles fit with a 2000-2001 RS LSD and the WRX LSD of course.
The RS MT diff is 4.11
The WRX MT diff is 3.90
The 1991 Legacy LSD is 3.90 but has unique axles.
WRX axles will not work with an open diff. or the Legacy LSD.

I think that covers it.
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Old 06-04-2003, 12:30 PM   #24
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so can i use my stock axles w/ a 4:11 open diff?
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Old 06-04-2003, 03:20 PM   #25
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You should be able to.

-Jon
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