3.90 to 4.11 conversion

93Leg-c · Post by **93Leg-c** » Sun Nov 07, 2004 6:23 am

What parts are needed for the conversion for a '93 AWD NA AT?

georryan · Post by **georryan** » Sun Nov 07, 2004 12:13 pm

Aren't you already a 4.11 if your NA?????

If you are....why would you go to a 3.9?? (other than gas milage)

93Leg-c · Post by **93Leg-c** » Sun Nov 07, 2004 4:34 pm

My ratio now is 3.90. I would like to have a 4.11.

And the way I drive, I actually get better gas mileage with a 4.11 than with a 3.90.

evolutionmovement · Post by **evolutionmovement** » Sun Nov 07, 2004 4:43 pm

An unresearched guess from a guy with a manual, but isn't the front diff a seperate section? If so, you may be able to get a front 4.11 and swap it on.

Steve

THAWA · Post by **THAWA** » Sun Nov 07, 2004 7:22 pm

you still have to remove the tranmission, then break open the whole case (because you have to change the whole ring and pinion), then change it, then find a 4.111 rear. Then you've got to wonder, if you have access to the front half of a tranny, where's the rear half of it? It would be quicker and more effcient to just grab a 4.111 tranny, and 4.111 rear diff and throw those bad boys on.

Although using the 3.9 gear ratios with the 4.111 final would make for some fast 1st and 2nd gears

93Leg-c · Post by **93Leg-c** » Mon Nov 08, 2004 9:21 am

I've never worked on an AWD system before so I'm not sure what's needed for the conversion. So, please bear with me if I ask seemingly unintelligent questions:

So, I basically need a new tranny and rear dif, both with 4.11 ratios?

But, aren't 4.11 trannies found only on WRXs? If so, will it be an exact swap with the Legacy tranny with no mods needed?

And I thought the 4.11 rear dif was also found on WRXs? Again, will it be an equal swap with no modifications?

Can I keep my tranny now and just install a 4.11 rear dif? That won't mess anything up?

So, the front dif is different than the tranny? (I told you I'd ask an unintelligent question or more)

Post by **Legacy777** » Mon Nov 08, 2004 3:10 pm

You'll need to find a 4.111 tranny from a 90-91 legacy at. The wrx ones won't work with your car.

It's possible a 95-99 will work, but I don't know the final drive ratios of them.

93Leg-c · Post by **93Leg-c** » Mon Nov 08, 2004 5:18 pm

OK, so I'll need a 4.111 tranny from a '90-'91 Legacy. And, I cannot just swap out the rear dif, right? (That would have been so much easier.)

If I locate a '95-'99 4.111 tranny from a Legacy or Outback, that should work? Or are electronics of any sort involved so that I would have to swap out sensors, ecu, or whatever?

Do I need a rear dif from a Legacy or will a 4.111 from a WRX work?

Now, the front dif. What is it? That's still a foggy term for me. Can someone make that clear to me, please?

Post by **Legacy777** » Mon Nov 08, 2004 7:32 pm

What do you mean....yeah you can just swap the rear diff...not sure I understand?

In 96 the phase 2 4EAT's were introduced. They have a different style connector that won't plug into your harness. So a 95 "should" work....the later models won't be plug and play....

any 4.111 rear diff will work.

The front diff for the automatics is a separate piece then the transmission however almost all transmissions that I've seen that get sold or bought have the diff included because it's pretty much part of the transmission....just a separate case.

93Leg-c · Post by **93Leg-c** » Tue Nov 09, 2004 6:38 am

Legacy777 wrote:What do you mean....yeah you can just swap the rear diff...not sure I understand?
.

I guess I don't always type what I'm thinking. What I was thinking was, it would have been so much easier to keep my 3.90 tranny and just swap out my 3.90 rear dif for a 4.111 rear dif--but I couldn't just do that because I need a 4.111 tranny to match the gearing with the 4.111 rear dif, right?

93Leg-c · Post by **93Leg-c** » Tue Nov 09, 2004 6:46 am

Legacy777 wrote:The front diff for the automatics is a separate piece then the transmission however almost all transmissions that I've seen that get sold or bought have the diff included because it's pretty much part of the transmission....just a separate case.

So, is it possible to just get the front dif and replace the 3.90 front diff for the 4.111 front diff as Steve mentioned? (Or is it not worth the trouble of doing that?)

Is that what THAWA was referring to when he said the ring and pinion have to be changed?

THAWA · Post by **THAWA** » Tue Nov 09, 2004 6:56 am

that's exaclt what I was referring to.

93Leg-c · Post by **93Leg-c** » Tue Nov 09, 2004 7:19 am

Gotcha.

And I've got a ways to go to understand everything but finally the picture is getting clearer.

Post by **Legacy777** » Tue Nov 09, 2004 3:25 pm

by the time you swap out the pinion gear....you would've been better off just getting a 4.111 tranny IMO.

93Leg-c · Post by **93Leg-c** » Tue Nov 09, 2004 5:02 pm

Yep, swapping the whole tranny rather than the front diff would be better for me since I've never been inside of any AT--I'm not ready for a new learning curve in that area, yet.

Although, THAWA posted something that now interests me: "Although using the 3.9 gear ratios with the 4.111 final would make for some fast 1st and 2nd gears." I assume by that post that the 3.9 tranny gearing is higher than the 4.111 tranny gear ratios. So, can the 4.111 ring and pinion be used in place of the 3.9 ring and pinion and still keep the 3.9 tranny gear ratios? And if that can be done, how much of a difference in acceleration would that make (after all, I'm looking for the best possible low- and mid-range pickup)?

93Leg-c · Post by **93Leg-c** » Tue Nov 09, 2004 5:11 pm

But, now going back 4.111 trannies. . .

Josh (or anyone else), the '96 and later trannies are not plug and play but are they just wiring connector differences or does it get more involved such as needing different ecus? Or are the differences in trannies due to physical differences, e.g. wider, longer, etc? Or are a combination of differences involved?

Post by **Legacy777** » Tue Nov 09, 2004 7:38 pm

1st and 2nd gear are lower on the n/a 4EAT's with the 3.90 final drive ratio. 3rd & 4th are the same.

93Leg-c · Post by **93Leg-c** » Tue Nov 09, 2004 7:57 pm

So then, it's possible to keep the lower 1st and 2nd gear ratios of the 3.90 tranny and replace the front diff and install the 4.111 front diff?

Post by **Legacy777** » Wed Nov 10, 2004 2:20 am

yeah....but it's a lot more work.

THAWA · Post by **THAWA** » Wed Nov 10, 2004 6:54 am

Do I have a problem explaining things? I'm not trying to be a dick by asking this so don't take it the wrong way, but did you not undestand what I said? Was I trying to say too many things at once? Please tell me so I can be clearer in the future. Seriously I'm not trying to be rude, I actually would like to know if I'm not explaining things right.

93Leg-c · Post by **93Leg-c** » Wed Nov 10, 2004 9:24 am

No, THAWA, it's that I sometimes don't get things right especially if I'm learning about it for the first time. In the past I've thought I understood something only to find out later that I missed something important. So, if I'm not really sure I understand it correctly, I ask again to get verification that my understanding is correct. I'm sorry if I've frustrated you or anyone else. But it's not you, it's me.

Would it help if in the future I said something to the effect, "So, could you verify this for me..." or "So, if I understand this correctly, ..." and then asked the question again?

Oh, and, thank you for explaining your feelings upfront. I really do appreciate it!

THAWA · Post by **THAWA** » Wed Nov 10, 2004 4:32 pm

ah okay. The only reason I ask is it seems like when i post a fair amount of info someone always misunderstands what I'm saying. Maybe I'm just being too impatient.

93Leg-c · Post by **93Leg-c** » Thu Nov 11, 2004 8:58 am

THAWA, now when I go back to your first post on this thread it makes a LOT more sense to me. I understand it now. You, and others on this board, have a lot more knowledge about all the different systems and components of the Legacys than I do so what is commonplace for you is not for newbies like me. So, it's probably just technical terms and a bit more knowledge that we newbies need and we'll be able to follow along perfectly well with your explanations.

Thanks for being patient.

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3.90 to 4.11 conversion

3.90 to 4.11 conversion