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 Post subject: rear subframe interchange
PostPosted: Thu Jul 21, 2016 1:05 pm 
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Joined: Thu Jul 21, 2016 12:17 pm
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What are my options for putting an AWD sub frame in the car in my sig? I know that the 89-94 AWD Legacy sub frame fits but are there any others. Those cars aren't common near me and the ones in the junkyard are there because they rusted out. Can I use a sub frame from a newer Legacy, Outback or Forester? Are there any that aren't a bolt in but are close to being compatible? I own a sawzall and a welder and would be willing to use those to make something that almost fits fit but if I'm going to go that route, depending on how involved it is I may as well copy a 89-94 sub frame from scratch or stuff a 8.8 based IRS up there since I have tons of 8.8 stuff lying around. Most of the research I've done has focused on the bolt-in stuff but if I can mod different sub frame to fit then I'll look into that.

Second question: What part of the AWD assembly conflicts with the gas tank? If it's the diff or drive shaft then I'll just leave those out until and use the FWD tank until I get around to installing an AWD trans.

Third question: Can I re-use the control arms from the FWD? It looks like I don't need new trailing arms as the FWD and AWD are the same part number. What about the lateral arms? They're not the same part number in the Subaru catalog but they don't look any different and the ones for sale online don't mention fitting AWD or FWD specifically.


I'd really like to slap a an AWD sub frame and knuckles under this now (current sub frame is fairly rusty) and then deal with the trans, diff gas tank, CV shafts, etc. at my leisure.

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'93 Legacy L, wagon, FWD, 2.2, automatic


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 Post subject: Re: rear subframe interchange
PostPosted: Thu Jul 21, 2016 6:06 pm 
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Welcome to the BBS.

You should be able to use a first gen Impreza rear subframe. I don't know of any major differences, but maybe others can comment. The second gen Legacy should also have the rear subframe.

As for the AWD components it's a little more complicated. The rear AWD knuckles have the CV shafts holding the bearing assembly and everything together. So if you were to not put in the rear diff or swap gas tank you would have to run the outer portion of the CV axles to keep the hub together.

You have to remove the rear subframe to install the gas tank so IMO it doesn't make sensor to install the AWD rear subframe have to use a make-shift outer cv axle just to pull everything out again. Just collect the parts and do it all at once.

Regarding the lateral links, I am trying to remember from my swap how they were different. I don't remember, but I think there may be a difference in the thickness of the part that bolts onto the subframe, but I can't confirm that. Someone else may be able to confirm. I would recommend getting the newer style lateral links from a first gen Impreza so you can add a rear anti-sway bar.

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: rear subframe interchange
PostPosted: Thu Jul 21, 2016 7:05 pm 
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Joined: Thu Jul 21, 2016 12:17 pm
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Legacy777 wrote:
Welcome to the BBS.

You should be able to use a first gen Impreza rear subframe. I don't know of any major differences, but maybe others can comment. The second gen Legacy should also have the rear subframe.

As for the AWD components it's a little more complicated. The rear AWD knuckles have the CV shafts holding the bearing assembly and everything together. So if you were to not put in the rear diff or swap gas tank you would have to run the outer portion of the CV axles to keep the hub together.

You have to remove the rear subframe to install the gas tank so IMO it doesn't make sensor to install the AWD rear subframe have to use a make-shift outer cv axle just to pull everything out again. Just collect the parts and do it all at once.

Regarding the lateral links, I am trying to remember from my swap how they were different. I don't remember, but I think there may be a difference in the thickness of the part that bolts onto the subframe, but I can't confirm that. Someone else may be able to confirm. I would recommend getting the newer style lateral links from a first gen Impreza so you can add a rear anti-sway bar.


So Legacy from 89 through 99(1st and 2nd gen) and Impreza through 2000 are my options for a 100% bolt in swap. Is that correct? I've seen sub frames listed as being compatible with 98-03 Impreza/WRX and Forester and 02-05 Impreza/WRX. I assume that's for a direct, bolt on fit with existing components so someone like me who doesn't have a bunch of other stuff (diff, suspension links T, brace, sway bar, etc) that the sub frame has to be compatible with might be able to get away with using anything in that range as long as the rest of the stuff I use is from a compatible application.


The CV being required to hold the unit bearing doesn't bother me. I'd want to have a set of stub shafts on hand anyway (for when I blow up a CV at 11pm on a Sunday) so cutting off the splined and threaded part of some junkyard CVs wouldn't be an issue.

Sway bar doesn't matter to me. Keeping the tires planted on unpaved surfaces does. If I have to get new links I'll just make my own adjustable links (bushing on one end, rod end style joint on the other). It'll be cheaper, beefier and adjustable (unsprung weight be damned). I'd only need to buy the threaded bungs and joints.

What about the differential? I was hoping to find a wrecked or rusted out 5spd donor with (matching front and rear ratios) and just swap that onto my sub frame whenever I get around to swapping to an AWD manual transmission. Is there somewhere with exactly what differentials and ratios were used in what vehicles?

Can the gas tank be dropped enough to access the sub frame without disconnecting everything on it?

I understand that it would be easier to do this all at once but the rear sub frame is pretty rusted out as are the lower coil perches on the struts. Up front the struts have the same issue and the top ring of the coil is broken a few inches in (same spot on both sides). I want to get the AWD suspension under there so I can do Forester struts all around, hopefully before the coils go through the lower mounts or the sub frame starts bending. My girlfriend DDs this from time to time so I can't count on being able to spot one of those things happening before they're a problem. Having to take everything apart a second time to get the driveline parts in there is really no big deal to me.

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'93 Legacy L, wagon, FWD, 2.2, automatic


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 Post subject: Re: rear subframe interchange
PostPosted: Thu Jul 21, 2016 10:31 pm 
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arse_sidewards wrote:
So Legacy from 89 through 99(1st and 2nd gen) and Impreza through 2000 are my options for a 100% bolt in swap. Is that correct? I've seen sub frames listed as being compatible with 98-03 Impreza/WRX and Forester and 02-05 Impreza/WRX. I assume that's for a direct, bolt on fit with existing components so someone like me who doesn't have a bunch of other stuff (diff, suspension links T, brace, sway bar, etc) that the sub frame has to be compatible with might be able to get away with using anything in that range as long as the rest of the stuff I use is from a compatible application.


The 02-05 Impreza stuff may work, but I'm just not sure. The earlier foresters are likely going to share the same subframe as the imprezas. You'll have better luck with the mid-90's stuff for compatibility assurance, but that doesn't mean some of the newer stuff wouldn't work....I just don't know.



arse_sidewards wrote:
What about the differential? I was hoping to find a wrecked or rusted out 5spd donor with (matching front and rear ratios) and just swap that onto my sub frame whenever I get around to swapping to an AWD manual transmission. Is there somewhere with exactly what differentials and ratios were used in what vehicles?


The rear subframe has two parts that connect the diff. The diff acts as a part of the rear structure with the Tee crossmember. Check out this picture. More pictures of my swap can be found here.

http://www.surrealmirage.com/subaru/ima ... P_3104.JPG

In theory you could just run the rear subframe and then add the rear diff and front tee crossmember later.

Check out these threads for ratios (where were in the drivetrain sticky thread, I recommend checking out the forum sticky threads).

http://bbs.legacycentral.org/viewtopic.php?t=32148

http://bbs.legacycentral.org/viewtopic.php?t=27119

Be aware that there are different style of differentials that require different drivelines and input flange.



arse_sidewards wrote:
Can the gas tank be dropped enough to access the sub frame without disconnecting everything on it?


The gas tank does not need to be touched to change the subframe. The subframe must be removed to change the gas tank.

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Josh

surrealmirage.com/subaru
1990 Legacy (AWD, 6MT, & EJ22T Swap)
1997 Impreza OBS

If you need to get a hold of me please email me rather then pm


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 Post subject: Re: rear subframe interchange
PostPosted: Fri Jul 22, 2016 12:16 am 
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Joined: Thu Jul 21, 2016 12:17 pm
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Ok, I'll look into foresters since they're common around here compared to 90s stuff. I'm probably going to have to buy a rear sub frame on line since pretty much everything here will be rusted out. I should be able to get the handful of brackets and stuff from a junkyard car. From there I wait for a transmission + drive-train donor. Not sure what I'm gonna do about the fuel tank. I hate using used fuel tanks here since everything is rusty. Hopefully I can find a junkyard car with a newish tank,

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