88whitecat Posted May 5, 2007 Share Posted May 5, 2007 ...While giving up the fight against sleeplessness:banghead: Anyway has anyone ever tried changing their diff gears? The front ones in particular? I was researching and found that 2.2mt legacys got 3.90 front and rear gears. being that I do alot of highway driving shorter gears would give better gas milage eh? and with gas climbing steadily (almost $3.25 here in ct) I look for every way to save. what do you all think, worth the project? Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted May 5, 2007 Share Posted May 5, 2007 Hi. I've never done it; I would guess it doable with the time and money. Probably would be easier to just swap out the rear diff than to try to switch out the gears. Not sure about the front diff; usually they just replaced with the trans as a unit but I'm not too familiar with the MT's. Can you maybe just run larger diameter tires? Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted May 5, 2007 Share Posted May 5, 2007 i think changing anything in the front differential is A LOT of work. first you pull the trans, then you remove the lower shaft(?) then you seperate the case... then you start in on the gears. there are 3 final drive ratios related to the legacy / outback, 3.9, 4.11, 4.44. assuming all 3 share the same 9 tooth pinion gear, the differences are the ring gear, 3.9=35 teeth, 4.11=37 teeth, 4.44=40 teeth. so in theory it is possible. but as i said, A LOT of work. why not just buy a manual trans. legacy.? Quote Link to comment Share on other sites More sharing options...
LosDiosDeVerde86 Posted May 5, 2007 Share Posted May 5, 2007 i think changing anything in the front differential is A LOT of work. first you pull the trans, then you remove the lower shaft(?) then you seperate the case... then you start in on the gears. there are 3 final drive ratios related to the legacy / outback, 3.9, 4.11, 4.44. assuming all 3 share the same 9 tooth pinion gear, the differences are the ring gear, 3.9=35 teeth, 4.11=37 teeth, 4.44=40 teeth. so in theory it is possible. but as i said, A LOT of work. why not just buy a manual trans. legacy.? what has 4.44's? Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted May 5, 2007 Share Posted May 5, 2007 what has 4.44's? based on my research, everything with 2.5L and automatic. outback, legacy GT, leg LSi, 2.5L/auto, 96-99 at least, maybe all the way to 07? Quote Link to comment Share on other sites More sharing options...
88whitecat Posted May 6, 2007 Author Share Posted May 6, 2007 why not just buy a manual trans. legacy.? Mostly because I'm lazy. I drive a 100mi+ daily round trip commute to work, and would rather have that one less thing to think about. I wanted one when I got my subaru about 2 years ago but the dealer only had a mt sport wagon and an at legacy L within my price range and I decided interior room was more important. Just thought it might be interesting to try with a spare tranny from a j/y so I could be driving right up to the point where I swap and its over quick to get it back on the road. Quote Link to comment Share on other sites More sharing options...
porcupine73 Posted May 6, 2007 Share Posted May 6, 2007 A j/y tranny could work. Make sure to get the rear diff from the same vehicle then too. Considering the cost and work in that, if fuel economy is the concern, how about other things (if they're not done already) such as tune up, fresh air filter, plugs&wires, maybe front o2 sensor, etc., low rolling resistance tires like on those hybrids, empty any excess cargo out of the vehilce, fuel efficent drivetrain lubes, etc. Quote Link to comment Share on other sites More sharing options...
johnceggleston Posted May 6, 2007 Share Posted May 6, 2007 A j/y tranny could work. Make sure to get the rear diff from the same vehicle then too. you are going to need 2 trans (or front diffs) and one rear diff matching the 'new' ring gear in order to have ready to swap. are the housings for the front diffs interchanceable from M/t to A/T? boy, that would save some work. Quote Link to comment Share on other sites More sharing options...
kimokalihi Posted May 6, 2007 Share Posted May 6, 2007 Not worth it at all. Believe me. I had to replace my A/T tranny in my 90 Legacy and the best one I found at the yard was a 94 with 140,00 miles on it. So I did the swap(MAJOR P.I.T.A)and then heard a grinding noise in the rear end. Turns out I think I started with 4.11 gearing and swapped the tranny which came with the front diff attached to it that was 3.90. I had to go back and get the rear diff to match. The car is now a little slower than it already was. I think this was the case, it could have been the other way around, 3.90 to 4.11. I don't remember nor do I know which means what. I get 25.5 mpg mainly going 50-55 mph. Gas in here is 3.50:eek: I'm saving for a diesel VW because 25 mpg just flat out sucks in my opinion. Plus diesel is FINALLY cheaper than gas here! YaY! Quote Link to comment Share on other sites More sharing options...
88whitecat Posted May 6, 2007 Author Share Posted May 6, 2007 when I got the car it was great, 28-30mpg highway 22-25city. Right now Im lucky to get 20mpg highway mostly due to aerodynamic drag from a damaged front end. I try everything else easy I can. I run the car empty and even started using acetone in the gas after reading a thread about that here. I need to fix it or relace it but I dont have the spare cash at the moment to do either. This is paid off so at this point it doesnt owe me anything and costs are limited to gas and maintnence. Quote Link to comment Share on other sites More sharing options...
jib Posted May 6, 2007 Share Posted May 6, 2007 when I got the car it was great, 28-30mpg highway 22-25city. Right now Im lucky to get 20mpg highway mostly due to aerodynamic drag from a damaged front end. I try everything else easy I can. I run the car empty and even started using acetone in the gas after reading a thread about that here. I need to fix it or relace it but I dont have the spare cash at the moment to do either. This is paid off so at this point it doesnt owe me anything and costs are limited to gas and maintnence. Just a thought, but it might be less expensive to fix the front end, than changeout gears. Taller, skinny tires, run at the high end of the tire manufacturers range would be the most economical way to pick up some mileage gains. The would definitely reduce your traction somewhat. Jack Quote Link to comment Share on other sites More sharing options...
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