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Old 02-08-2013, 04:14 PM   #1
MikeC5
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Default Gearing Options for MT 2002 Outback?

I have a stock '02 Outback (NA 2.5 motor) that I really like with one exception; the (5 speed) tranny and differential gearing result in unnecessarily high revs when highway cruising (about 3200 rpm at 65 mph, if I can believe the gauges). We also have a '02 and '03 Forester with 4EAT and they are something like 500 rpm lower at same indicated speed. As much as I'd like to swap in a 6 speed, the threads I searched through make it fairly clear this wouldn't be a simple tranny swap - at minimum it appears driveshaft, front axles and maybe struts would have to be sourced too. While I'm not afraid to tackle something like this from a wrenching standpoint (it would be fun!), it would be prohibitively expensive I'm sure.

So another option might be to change the differential gearing. Can anyone tell me if a 5 speed Forester of correct vintage were sourced what besides the transmission (the whole enchilada) and rear diff would be needed? This assumes the Forester is geared differently than the Outback but maybe it's only a difference between MT and 4EAT vehicles?
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Old 02-08-2013, 05:13 PM   #2
Patrick Olsen
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I don't know about the 2nd gen Outbacks, but the 1st gen Legacy Outbacks just used a different 5th gear. It was about 10% different, I believe to account for the Legacy Outback's taller tires (compared to the normal Legacys). I swapped the Outback 5th (0.871:1, as I recall) into my 2.5GT's 5MT (which had a 0.780:1) to give the car better acceleration on track. Definitely put the highway RPMs up there (about 20:1, so 80mph @ 4k), but it made a very noticeable difference on the long straights at VIR and Summit Point.

If you check the Transmission & Driveline forum there's a sticky thread (or a thread in the "threads of note" sticky) with all sorts of gear ratio information. I've got a bunch of stuff saved at home, I'll try to remember to check later today.
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Old 02-08-2013, 05:17 PM   #3
MikeC5
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Thanks Patrick. I have been searching over there and it appears there was a spread sheet available with a lot of information for various models. Unfortunately, the links I was able to find to it were dead...
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Old 02-08-2013, 08:00 PM   #4
drewmob
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I thought the same thing about an old 99 LOB that I had so I swapped in an Impreza L trans with similar gearing and a 3.90FD instead of the 4.111. BAD idea. That thing was slower than Christmas and bogged off the line unless you goosed it.

I'm sure there are solutions but it would require a custom build.
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Old 02-09-2013, 11:07 AM   #5
Patrick Olsen
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This is the thread I was thinking of, but it doesn't have much info on newer models, nor does it have much info on Legacys/Outbacks/Foresters. This post has a decent summary of gear ratios, but it's missing the '00-04 Legacys.

This list is a bit more comprehensive, but it's not without its own inaccuracies. It shows that the '01 and '02 Legacy Outback went to a 3.90 final drive, but all the rest of the '00+ years are 4.11. I'm not sure I believe that, and doing the math I think proves I'm right. (With 3.90s and stock 225/60-16 tires, 65mph would be 3090rpm; with 4.11s it would be 3246rpm. The latter matches what you're seeing.) So, I think you can ignore that 3.90 final drive that it lists for your model year, and doing so opens up quite a few options for you - looks like there are multiple Forester, Impreza and Legacy options that have the same 4.11 gears but use the higher (lower numerically) 5th gear for lower highway cruise RPMs so you could swap the whole tranny and not worry about changing out the rear diff. The other option would be to source just the 5th gear parts for either the 0.780 or 0.738 ratio and throw that into your existing transmission in place of the 0.871.

Do you have the Owners Manual for the car? I think it might have the gear ratio info in it somewhere, in which case you could confirm the 3.90 vs 4.11 issue.

Quote:
Originally Posted by drewmob View Post
I thought the same thing about an old 99 LOB that I had so I swapped in an Impreza L trans with similar gearing and a 3.90FD instead of the 4.111. BAD idea. That thing was slower than Christmas and bogged off the line unless you goosed it.
Yeah, I was thinking the same thing. I think the key is to find just the 5th gear he wants, and make sure to stick with the same final drive he's got now. The '00-04 Outbacks are pretty sluggish to begin with; changing to a 3.90 final drive would help the highway RPMs, but would make the car even more of a dog.

Last edited by Patrick Olsen; 02-11-2013 at 05:21 PM.
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Old 02-10-2013, 07:40 PM   #6
MikeC5
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Thanks guys. I dug into the FSM for the Outback and it does show 4.111 with 0.871 ratio 5th. I did also dig up a thread on changing out the 5th gear set which doesn't sound too terribly difficult (I was planning to pull the engine to do a clutch and fix some oil leaks soon anyway). It appears I have a choice of 0.73 and 0.78 for 5th.
http://forums.nasioc.com/forums/show....php?t=2218907
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