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Downside to 3.9 ratio


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43 replies to this topic

#1 ShawnW

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Posted 10 October 2012 - 10:40 PM

My 95 Outback has the TY752VAAAA trans with 4.11 gears and I have a spare trans lying around that is from a 98 Impreza, TY752VA5AA and 3.90 ratio.

I am thinking about putting a Frankenmotor together as the original engine has a thrust bearing play problem, and the input shaft bearings on the trans are toast too so was going to put it together.

The car is pretty decent right now in the power and gas mileage department. What would you expect would change with these changes? Still fun but a gas saver with the gears or just not worth losing the 4.11?

#2 spazomatic

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Posted 10 October 2012 - 11:50 PM

that's a pretty small ratio change, I don't think itd be a big loss. Youd need to change your rear diff too, though.

#3 kanurys

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Posted 11 October 2012 - 12:30 AM

I don't think it would be much of a problem with the increase in low end torque from the frankenmotor. Maybe they'd balance each other out?

#4 ShawnW

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Posted 11 October 2012 - 01:18 AM

Which is kindof what I was worried about too. If I am going to put a 2.5 bottom end in and 2.5 head gaskets in and lose what I had in the 2.2 with higher gears it might not be worth it.

#5 grossgary

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Posted 11 October 2012 - 06:00 AM

might be able to make up for it at the wheel? get a bit smaller or bigger tire/wheel combo to make up the difference?

#6 CoupedUpSubie

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Posted 11 October 2012 - 07:09 AM

Not sure how much of a difference 200 rpm makes. I calculated engine speeds at 60 mph and thats what I found for a difference between the two transmissions.

The 4.111 trans will have your car doing 61 mph at 2700 rpm. Compared to 64 mph with the 3.9 trans at 2700 rpm.

#7 edrach

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Posted 11 October 2012 - 09:32 AM

Finally something I had experience with. I had swapped our '97 Impreza from 3.900 to 4.111 to get more "dig" off the line since it was my rallycross car along with daily driver. At highway speeds I was running about 500 rpm higher in 5th. Check the transmission info in the USRM to match the ratio along with the ratio in 5th to see how many rpm you will change in that gear.

Oddly enough, we're changing the '97 back to 3.900 since it will become a DD for my sister in law and lower rpm in 5th and slightly better gas mileage is an issue for her.

#8 CNY_Dave

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Posted 11 October 2012 - 02:27 PM

It's a 5.1 % change, so take whatever revs you have now at any speed/gear and multiply by (1 - 0.051).

#9 kanurys

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Posted 11 October 2012 - 04:25 PM

Hey, you might even get better gas mileage with the 3.9. :) (Just do it)

#10 Fairtax4me

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Posted 11 October 2012 - 04:42 PM

It will make a difference, but the extra power of the Frankie will certainly overcome the ratio difference. Fuel economy depends mostly on how you drive and what speed you drive anyway. I can get over 30mpg out of my Legacy on the highway ~55 mph. But at interstate speed ~70-75 mph that drops to about 26 mpg.

#11 johnceggleston

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Posted 11 October 2012 - 04:45 PM

My 95 Outback has the TY752VAAAA trans with 4.11 gears

are you sure it is 4.11 ratio?

the ...AAAA trans was used from march of 94 - dec of 95 according to opposed forces.
click on usage info.
http://opposedforces...nfo/32000AD010/

the 3.9 pinion and ring gear were used in the ''outback'' starting in july of 95 - july 97.
click on usage info.
http://opposedforces...nfo/38104AA010/

i don't have enough reliable info, and it seems hard to come by, to say it is not a 4.11 trans, but i would make sure before you base any expensive decisions on it. but considering what you are talking about doing i doubt it makes much difference.

but if you want a 4.11 ratio from a manual trans just use one from 92 - 94 legacy or a 97 - 99 outback. (the 92 - 94 speedo gears will match your car.)

but i'm still not sure the 95 outback manual trans had the 4.11 ratio. i'm not sure it does not either.

the legacy L 5spd didn't have one.
5spd trans, 95 - 99 legacy L, brighton, ej22 has a 3.9 ratio.
auto trans, 95 - 99 legacy L, brighton, ej22 has a 4.11ratio.

HTH

Edited by johnceggleston, 11 October 2012 - 05:16 PM.


#12 edrach

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Posted 12 October 2012 - 06:32 PM

are you sure it is 4.11 ratio?

the ...AAAA trans was used from march of 94 - dec of 95 according to opposed forces.
click on usage info.
http://opposedforces...nfo/32000AD010/

the 3.9 pinion and ring gear were used in the ''outback'' starting in july of 95 - july 97.
click on usage info.
http://opposedforces...nfo/38104AA010/

i don't have enough reliable info, and it seems hard to come by, to say it is not a 4.11 trans, but i would make sure before you base any expensive decisions on it. but considering what you are talking about doing i doubt it makes much difference.

but if you want a 4.11 ratio from a manual trans just use one from 92 - 94 legacy or a 97 - 99 outback. (the 92 - 94 speedo gears will match your car.)

but i'm still not sure the 95 outback manual trans had the 4.11 ratio. i'm not sure it does not either.

the legacy L 5spd didn't have one.
5spd trans, 95 - 99 legacy L, brighton, ej22 has a 3.9 ratio.
auto trans, 95 - 99 legacy L, brighton, ej22 has a 4.11ratio.

HTH

It's a 4.111; from the transmission chart in the USRM:
US Legacy Outback MY94 TY752VAAAA 3.545 2.111 1.448 1.088 0.780 N/A 3.416 1.000 4.111 Viscous (4kgf) Open

Easier to see here:
http://www.gearhack....nsmission Chart

#13 johnceggleston

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Posted 12 October 2012 - 08:32 PM

i cannot argue with that chart. but if i remember correctly, the chart has been wrong in the past.

but it does appear that the ......AAAA trans was a 94 trans that was used in the 95 outback. and that would mean that it has a 4.11 ratio.

nothing i said above contradicts this.

i just wanted confirmation before some one spent engine / trans dollars on incorrect info. the outback manual trans is apparently the only manual trans produced in 95 that had a 4.11 ratio. ALL other 5 speeds in 95 had a 3.9 ratio.

glad the ratio is confirmed.

but again, if a 4.11 ratio is needed, get one from a 96 - 98 outback.

#14 edrach

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Posted 12 October 2012 - 08:37 PM

I sometimes wonder if Fuji just randomly picked transmissions and rear diffs when assembling their cars. Having made the 3.900 to 4.111 swap once and now back again, I'm beginning to believe they do. When I was looking for a 3.900 transmission for the Impreza, Every year from '94 to '98 had both the 4.111 and 3.900 transmissions available for the Legacy and Impreza models.

I'm not a true expert, but I've never found the chart to be inaccurate. Doesn't mean it couldn't be, but.......

#15 johnceggleston

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Posted 12 October 2012 - 08:51 PM

i must say, the early 90s were confusing. but the late 90s were fairly consistent.

ej22
4.11 for the auto trans
3.9 for the 5 spd trans

ej25
4.44 for the auto trans
4.11 for the 5spd trans

the 95 outback 5spd is the odd ball and does not match the above info.

and the 96 outback 5spd is different as well. it has the ej22 but it has the 4.11 5spd trans. it would fit the trend if it had the ej25 engine, but it doesn't.

as soon as i think i know something, i learn something new.

#16 edrach

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Posted 12 October 2012 - 10:30 PM

In my case, I wasn't even looking at the automatic transmission; just the manual 5 speed and found both ratio versions in the years I was looking for. Generally, the EJ18 engines had the 4.111 and the EJ22 had the 3.900. But there were exceptions to that rule too. I'm afraid we might be beating this topic to death. Suffice it say, check the chart to be sure; or if pulling a gearbox at the junkyard take the rear diff too.

Edited by edrach, 12 October 2012 - 10:33 PM.


#17 edrach

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Posted 12 October 2012 - 10:43 PM

but again, if a 4.11 ratio is needed, get one from a 96 - 98 outback.


I was lucky enough to find a 4.111 transmission out of a '95 WRX when a friend bought a Japanese front clip for the engine and sold me the transmission. It also had the advantage of being a close ratio box which served me well when my daily driver was taken to the rallycross course.

Transmission was a TY752VB3FA (from a ’95 JDM WRX Impreza). Cost me a little in gas mileage and extra rpm at highway speeds, but I didn't care about that.

#18 wally

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Posted 13 October 2012 - 06:58 AM

but if i remember correctly, the chart has been wrong in the past.


yes, it has been. it was incorrect for my '95 leg wagon. i don't remember the specifics, but it "claimed" the code from my transmission came from a different year, yet it was the factory original (which i replaced when i lost the synchros in 3rd and 5th, along with having it pop out of 3rd and 4th). the tag on the fender matched the numbers on the transmission bh.

#19 edrach

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Posted 13 October 2012 - 09:45 AM

yes, it has been. it was incorrect for my '95 leg wagon. i don't remember the specifics, but it "claimed" the code from my transmission came from a different year, yet it was the factory original (which i replaced when i lost the synchros in 3rd and 5th, along with having it pop out of 3rd and 4th). the tag on the fender matched the numbers on the transmission bh.

There seems to be some overlap in the years. For example, the production run for a '95 might start in Sept of '94 and the VIN plate will have the actual date of manufacture as 9/94, but the car is built to '95 specifications and is delivered as a '95 model. I've seen that discrepancy on the chart a few times, but the data for the final ratios from the chart have always matched what I found in the transmissions I've installed. I can't speak for the actual gear ratios for 1st through 5th since I've never had to look at that. But as long as the front diff and rear diff matched I didn't care.

#20 wally

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Posted 13 October 2012 - 06:04 PM

chart "claimed" i had 4.11 gears. i have 3.90s.

#21 edrach

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Posted 13 October 2012 - 06:29 PM

chart "claimed" i had 4.11 gears. i have 3.90s.

I can't argue with that. Just so I know in the future, since it won't be the last time I might switch out transmissions, do you remember the transmission number?

#22 wally

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Posted 13 October 2012 - 06:43 PM

Ty752vaaaa

#23 johnceggleston

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Posted 13 October 2012 - 09:39 PM

that is the same trans listed in the original post.

how did you learn you have a 3.9 ratio?????

#24 wally

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Posted 14 October 2012 - 07:41 AM

it had the TY752VAAAA transmission originally, which the chart claims is 4.11.

i replaced it with a transmission from an impreza, coded TY752VT3AA, which the chart lists as 3.90.

i did not change or replace the rear differential, and i have been driving it since i installed the "replacement" transmission in july 2010. thus, my original, or the replacement, does not have the gearing claimed via the "chart".

additionally, the TY52VAAA isn't listed for model year '95 legacy wagons. it's listed as model year '94 outback (i know they didn't exist in '94, at least in the us). according to the chart, my original transmission should have been coded TY752VABAA, which has (according to the "chart") 3.90 gears. clear as mud?

regardless, one of the listings is incorrect, else i would have munched the rear or center diff by now.

Edited by wally, 14 October 2012 - 08:36 AM.


#25 wally

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Posted 14 October 2012 - 09:02 AM

to the original poster, i'd verify that your existing transmission does, in fact, have 4.11.

my original transmission was coded exactly the same as yours (and matched the factory tag on the fender, next to the strut top). i believe it really had 3.90, especially since the replacement transmission is supposed to have 3.90, and i didn't change/replace the rear diff.




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