keltik Posted August 14, 2009 Share Posted August 14, 2009 Harro all! Its been a while. Im looking to change my transmissions final drive ratio from a 4.111 to a 3.9 or a 3.7 over the summer. Ive killed my front differential so the transmission has to come out sooner or later and i figured i might as well look into doing this swap at the same time. Has anyone done this? Ive seen a couple of kits advertised for converting USDM WRX's from 3.9 to 4.444 so its definately possible. Looks like i need to change the pinion shaft and front crown wheel. I know its a long shot but does anyone have any more information on this mod? Link to comment Share on other sites More sharing options...
4x4_Welder Posted August 15, 2009 Share Posted August 15, 2009 What's your car and transmission? Link to comment Share on other sites More sharing options...
keltik Posted August 15, 2009 Author Share Posted August 15, 2009 2002 Legacy (EZ30D) with a TY752 manual trans from a 1994 Legacy GT (EJ20H). Cruising RPM is about 3,000rpm for 60mph and i run out of revs in 5th at 135mph Link to comment Share on other sites More sharing options...
edrach Posted August 16, 2009 Share Posted August 16, 2009 2002 Legacy (EZ30D) with a TY752 manual trans from a 1994 Legacy GT (EJ20H). Cruising RPM is about 3,000rpm for 60mph and i run out of revs in 5th at 135mph I'm pretty sure you have a 4.111 now (check the transmission charts in the USRM) to be sure. It's pretty easy to swap in a 3.900 transmission along with a 3.900 rear (check the charts again to see where to look). Thats certainly easier than changing the front pinion and rings gears AND the rear diff to match. I'm not sure why you want to make the change. Having driven both versions in my '97 Impreza, the primary difference is that the 4.111 has more pickup and you'll need to shift down less on hills. The 3.900 version is a little doggy in comparison and runs out of power on hills sooner forcing you to shift down. Oddly I never noticed a difference in gas mileage. Of the two, I certainly preferred the 4.111. Link to comment Share on other sites More sharing options...
keltik Posted August 16, 2009 Author Share Posted August 16, 2009 (edited) Yup its a 4.111 at the moment. The main reason i just want to swap the final drive ratio instead of the whole transmission is a clutch issue. Turbo models here have MUCH stronger clutches and cant be swapped into a non turbo case. I want a good strong clutch and a lower cruising rpm. I dont think a non turbo EJ20 clutch would stand up very long to the torque and power ill be making. The other reason is gear ratios. The lower final drive ratio transmissions also came with higher gear ratios to compensate. So by swapping the crown wheel and pinion out of one of those into my transmission ill see a bigger gain than just swapping the whole thing. A 500rpm drop would make a bigger difference to my fuel economy compared to that on a EJ22 or whatever your Impreza has. I put a 4.444 final into my old turbo 1989 Legacy and it was a total blast to drive around town - but that car wasnt built for long distance driving. Edited August 16, 2009 by keltik Link to comment Share on other sites More sharing options...
johnceggleston Posted August 16, 2009 Share Posted August 16, 2009 (edited) when subaru introduced the 2.5L engine in the us it was always paired with the lower geared final drive, 4.11 manual, 4.44 auto, in the legacy any way. but they also always used larger diameter tires which mostly off set the lower gearing. (the one exception was the 96? - 99? GT which had legacy size tires.) as a result there isn't a great difference in how the legacy and the outbcak drive, except for the increased power in the 2.5l. and the lower miles per gallon is the result of the larger engine, not the lower gearing. the point is this, would larger tires accomplish the lower rmp you are looking for? would you need longer struts for larger tires? just a thought. EDIT: i corrected this post after edrach pointed out my error. the next post may be slightly confusing as a result. Edited August 16, 2009 by johnceggleston Link to comment Share on other sites More sharing options...
edrach Posted August 16, 2009 Share Posted August 16, 2009 (edited) when subaru introduced the 2.5L engine in the us it was always paired with the lower geared final drive, 4.44 manual, 4.11 auto, in the legacy any way. but they also always used larger diameter tires which mostly off set the lower gearing. (the one exception was the 96? - 99? GT which had legacy size tires.) as a result there isn't a great difference in how the legacy and the outbcak drive, except for the increased power in the 2.5l. and the lower miles per gallon is the result of the larger engine, not the lower gearing. the point is this, would larger tires accomplish the lower rmp you are looking for? would you need longer struts for larger tires? just a thought. John, I think you have it reversed; the 4.44 rear ratio was for the automatics. ALL US Impreza and Legacy models from '94 to '05 were either 3.900 or 4.111 for the manual transmissions (check out the chart from the USRM: http://www.gearhack.com/myink/ViewPage.php?file=docs/Subaru%20Transmission%20Chart). It's my understanding that the 4.44 transmissions were all automatics, but I can't reference any documentation for that other than my '99 Forester FSM which lists a 4.44 rear diff for the automatic transmission model. To the original poster: You might find the chart useful in selecting a transmission with a 3.900 ratio that can handle the extra HP of your turbo model and that fits. Edited August 16, 2009 by edrach Link to comment Share on other sites More sharing options...
johnceggleston Posted August 16, 2009 Share Posted August 16, 2009 (edited) John, I think you have it reversed; the 4.44 rear ratio was for the automatics. It's my understanding that the 4.44 transmissions were all automatics, you're right, i mixed them up, poor dumb brain. sorry, i will correct. Edited August 16, 2009 by johnceggleston Link to comment Share on other sites More sharing options...
keltik Posted August 16, 2009 Author Share Posted August 16, 2009 Well its a good thought with the tires, but im already running 17inch rims with 215/45 tires. Theres not a lot of clearance left to run anything bigger, or at least not usefully bigger. As far as the power goes, its just a H6 outback motor. When it was coupled to an automatic trans it had a 4.111 final drive and a 0.694 4th gear. With the manual, 5th gear is only 0.825. 60mph now comes at 3,000rpm instead of 2,200rpm. So thats a pretty big difference to the cruising rpm the motor was designed to be efficient at. Anyone whos driven a H6 - its like being stuck in 3rd all the time. Link to comment Share on other sites More sharing options...
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