glennda5id Posted July 24, 2012 Share Posted July 24, 2012 Is it possible and/or advisable to take a 4EAT set up for AWD and configure it for 2WD by removing the center diff and rear output shaft and covering up the hole? I ask this question because I need to replace the trans on my 2WD Legacy, however it might be of interest to folks who are doing special applications like building a mid engine car. This is one of those special projects and I think they do it, but I don't know how. http://www.factoryfive.com/kits/project-818/ Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted July 24, 2012 Share Posted July 24, 2012 (edited) Most people just disable the Awd by putting a fuse in the FWD fuse holder and remove the rear section of the driveshaft. For a swap like you're talking about I have heard of people just covering the output shaft. There is no need to remove any internal parts though, the automatics drive the front wheels all the time and just vary power to the rear with a set of clutches. I suppose if you wanted to shed some weight you could remove the transfer clutches, but it's not really necessary for the trans to operate. Edited July 24, 2012 by Fairtax4me Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 24, 2012 Share Posted July 24, 2012 if you open the rear extension housing and remove the clutch drum and output shaft with bearing you will be left with a fairly simple hole to plug. my back ground is in bath remodling so i thought a type of plumbing pipe plug could be retro fitted. but it doesn't seem like it would take much. the other thing to consider is the FWD and AWD may have different rear mounts. i'm assume the mounting points are there for both but just be aware. Quote Link to comment Share on other sites More sharing options...
presslab Posted July 25, 2012 Share Posted July 25, 2012 The FWD 4EAT has a different upper reduction gear, without the transfer clutch basket. The AWD output shaft can't be simply removed as it supports the end of the intermediate shaft, the FWD end cover has a different bearing here. If you want to convert from AWD to FWD I think these are the parts to do it: intermediate shaft (with upper reduction gear), lower reduction gear (they're a matched set), and FWD end cover with bearings. I haven't tried this though. I imagine it's easier (although not as clean) to just cap the AWD output somehow. Quote Link to comment Share on other sites More sharing options...
Ricearu Posted July 25, 2012 Share Posted July 25, 2012 just install the carrier bearing and front driveshaft section from the awd car. easy peasy. I have put 10k on my current legacy sedan just like this. Quote Link to comment Share on other sites More sharing options...
glennda5id Posted July 25, 2012 Author Share Posted July 25, 2012 (edited) So it sounds like removing the AWD part of it is sort of out of the question. If I use this transmission. Is it bad on the transmission to just run it as is with no rear driveshaft attached? The trans will be hooked up to a TCU that won't have any wiring for the duty C solenoid so the duty solenoid will not be energized. Is this an issue? Edited July 25, 2012 by glennda5id Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted July 25, 2012 Share Posted July 25, 2012 Grossgary might have some further ideas, I think he converted a AWD Impreza to FWD and surmounted this challenge somehow. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 25, 2012 Share Posted July 25, 2012 (edited) The FWD 4EAT has a different upper reduction gear, without the transfer clutch basket. The AWD output shaft can't be simply removed as it supports the end of the intermediate shaft, the FWD end cover has a different bearing here. you have to plug / cover the output shaft some how. with out the drive shaft the ATF will pill out on the ground. i understand what was said about the ''carrier'' bearing in the FWD rear cover and how it supports the what ever shaft / gear, but i'm not 100% on how that eliminates the chance of removing the rear output shaft and clutch basket / drum. based on the way it is designed, it seems to me the rear of the trans shaft is getting very little , if any, support from the transfer clutch drum and the rear output shaft / bearing. it reminds me a little of a long board sitting on 2 saw horses while you try and saw it in half in the middle. at some point there is going to be movement in the middle . because of where the trans shafts are supported there is going to be some, maybe lots of, slop or play in the clutch drums / baskets where they fit together. but i have very little experience inside a trans and i would hate for someone to try removing the rear shaft and end up ruining a trans and wasting money based on my in-experienced advice. i know the bearing on the rear output shaft is a engineered and tight support point and i guess since there are no lateral forces at play on the shaft at either end (although the drive shaft carrier bearing COULD allow for some, maybe, i guess)... i guess the clutch basket / drum could supply support for the trans shaft. it just seems an odd way to design something that you didn't want to slop around. an extra bearing or support point for either shaft would seem like much better design from an engineering point of view, i would think, maybe. but idk. what am i missing.? Edited July 25, 2012 by johnceggleston Quote Link to comment Share on other sites More sharing options...
bluedotsnow Posted July 25, 2012 Share Posted July 25, 2012 first of all I can say from personal experience when you totally remove any RWD from an AWD subaru it will eat front cv axles! I imagine this can be avoided by using axles and possibly axle stubs from a FWD car as they are stronger. these cars suspension were not designed to be FWD and I could very much feel the instability of the rear end. when I was having problems I went from having the solenoid fail with some atf pressure to the rear section to NO pressure after winters auto left a gasket and backing plate off. I did notice a difference and my front cv axles were torn apart within a few weeks! a friend also pointed out that when in this bungled FWD mode the car would downshift more than normal due to slight differences in wheel ration. if you want to do this mod do it all the way and use a FWD ECU and TCU I think the TCU is the same just no duty c wiring and or circuitry this means you wont have a code thrown constantly due to an AWD TCU lack of duty c signal. conversely I have heard of some people making the 4eat strictly RWD but I gotta say I bet that eats rear cv axles and or clutch packs unless you do the pin mod and lock your clutch pack at all times with metal pins(not advised). be nice to your subie, maintain and appreciate its AWD it will save your life when a FWD car will kill you! Quote Link to comment Share on other sites More sharing options...
glennda5id Posted July 25, 2012 Author Share Posted July 25, 2012 So my legacy is a 2WD and I need a new trans and have access to a low miles AWD trans for a great price. I'm trying to figure out if this AWD trans will work and if I can remove the rear drive shaft or if its okay to leave it in there. I have access to a 2WD 4EAT that I can swap parts from. Could I take parts from my 2WD to turn my 4EAT AWD into a 2WD. My other question is, with no power to the duty C, my understanding is that the center diff will be locked at 50/50. Does this matter with nothing hooked up to the rear output shaft? I would love more than anything to turn that car into AWD, but that is a lot of work and cost. Quote Link to comment Share on other sites More sharing options...
presslab Posted July 25, 2012 Share Posted July 25, 2012 Could I take parts from my 2WD to turn my 4EAT AWD into a 2WD. Yes. You will need to move the parts I mentioned, the intermediate shaft with gear (the upper one), the whole thing should slide out with a bit of prying. And the lower gear, you'll need a gear puller for this, and a new pinion nut. Make sure to mark the gear teeth mating before you pull them apart so you put them back together with the same teeth touching. And then of course use the FWD rear cover. My other question is, with no power to the duty C, my understanding is that the center diff will be locked at 50/50. Does this matter with nothing hooked up to the rear output shaft? This won't cause a problem, but you'll need to keep the output shaft in place and somehow cap the end so the fluid doesn't leak out. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted July 25, 2012 Share Posted July 25, 2012 so if you swap in a AWD trans and want to run it in FWD only the easiest way to do it is to install the FRONT section of the drive shaft from the AWD car the trans came from. but leave the rear section of drive shaft off. with out the front section of drive shaft the ATF will run out through the output shaft. the seal located there actually is supposed to seal to the front most section of the drive shaft. i ASSUME all the ''bolt holes'' for mounting the AWD rear trans mount and cross member (different than the FWD) and the drive shaft carrier support bearing mounting bracket (the cross member at the mid point of the drive shaft), i assume all those bolt holes will be there. you may have to clean them up in order to use them. this is an educated guess based on the fact that it is cheaper for subaru to put all the bolt holes on all the chassis rather just the AWD holes on the AWD cars. but the deal breaker for the ''really cheap'' AWD trans may be the cost of the front section of the drive shaft. you have to have this and if it cost money it may over price the AWD trans. making it more than a local FWD trans. Quote Link to comment Share on other sites More sharing options...
glennda5id Posted July 25, 2012 Author Share Posted July 25, 2012 Pesslab, I'm confused, I will be leaving in the rear output shaft but swapping the rear cover from the 2WD 4EAT? How will that work? Quote Link to comment Share on other sites More sharing options...
presslab Posted July 25, 2012 Share Posted July 25, 2012 Pesslab, I'm confused, I will be leaving in the rear output shaft but swapping the rear cover from the 2WD 4EAT? How will that work? One of your options is to keep the "center diff" (which is part of the output shaft) and the answer to your question is that being locked won't cause a problem. The other option is to replace the intermediate shaft and gears, and you will no longer have a "center diff" or an output shaft, so obviously this is not a problem either. The "center diff" is really a transfer clutch. Quote Link to comment Share on other sites More sharing options...
glennda5id Posted July 25, 2012 Author Share Posted July 25, 2012 If I take option 2, basically leave everything alone, is there going to be any loss in power or efficiency to the front wheels. Is it bad to just leave the rear output shaft. If I leave it, it shouldn't leak as there is a seal there already. This would be the equivalent of having an AWD car and removing the rear drive shaft. Also, one of the posters mentioned different different mount locations for the two transmissions. I have heard of folks putting a 2WD 4EAT into a AWD Subaru, I assume I can do the reverse. Quote Link to comment Share on other sites More sharing options...
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