Swapping a 1994 Legacy SS 4eat and rear diff into my 1990 NA

voodoochylde · Post by **voodoochylde** » Tue Feb 06, 2007 2:00 am

I found an extremely nice gentleman on the forums that may sell me his transmission.

It's a 3.90 4EAT transmission and rear differential. Mine's a 1990 Legacy NA with the 4.11 equivalent.

What would I need to do the swap? Just the tranny/diff? Will my TCU control the newer tranny? Will my axles work?

Thanks in advance!

555BCTurbo · Post by **555BCTurbo** » Tue Feb 06, 2007 4:34 am

I think you might need the Turbo TCU...

If so I have one that I could hook you up with for cheap

Post by **Legacy777** » Tue Feb 06, 2007 6:51 pm

You'll probably be fine with your existing TCU.

Is the tranny from a turbo or non-turbo legacy?

voodoochylde · Post by **voodoochylde** » Tue Feb 06, 2007 10:42 pm

555BCTurbo, nice name and thanks for the offer. I'll keep ya in mind.

Legacy777, it's from a turbo legacy. Since I'll have relative ease locating a TCU, I'm more worried about the axles/stubs. Am I correct thinking the only different axles in this year range (1990 - 1995) were between LSD and non-LSD?

AWD_addict · Post by **AWD_addict** » Wed Feb 07, 2007 2:47 am

I know that a NA 4.111 4EAT will work normally with a TCU from a TW's 3.90 4EAT.

You're probably correct about the axles.

voodoochylde · Post by **voodoochylde** » Wed Feb 07, 2007 4:01 am

AWD_addict wrote:I know that a NA 4.111 4EAT will work normally with a TCU from a TW's 3.90 4EAT.

You're probably correct about the axles.

Meaning...the turbo wagon's TCU has enough brainpower to control another 4eat...hopefully that means my NA's TCU is as smart

Thanks for the input

Post by **Legacy777** » Fri Feb 09, 2007 7:09 pm

The axles are the same, so you shouldn't have a problem.

wtdash · Post by **wtdash** » Thu Jul 05, 2007 7:02 pm

voodoochylde
I'm doing a similar swap, except I'm replacing my '90 w/a 4EAT and LSD rear diff from a '91.

Did your swap go as planned?

I'm looking for any/all info that my Haynes manual may leave out.

Thanks!

AWD_addict · Post by **AWD_addict** » Mon Jul 09, 2007 1:26 am

voodoochylde wrote: Meaning...the turbo wagon's TCU has enough brainpower to control another 4eat...hopefully that means my NA's TCU is as smart

Thanks for the input

Sure. If it can't do it, I have a turbo TCU for sale.

Coy · Post by **Coy** » Wed Jul 11, 2007 8:33 pm

so that means that if i got a rear section of a driveshaft from a 90 n/a 5 speed it would fit into my 92 n/a 5 speed, no fuss no muss.

i hope cause its the only option ive found to get my problems taken care of.

wtdash · Post by **wtdash** » Wed Jul 11, 2007 10:39 pm

Coy wrote:so that means that if i got a rear section of a driveshaft from a 90 n/a 5 speed it would fit into my 92 n/a 5 speed, no fuss no muss.

i hope cause its the only option ive found to get my problems taken care of.

If the driveshaft includes the rear diff see below:

I believe the '90-'91 are 4.11 rear dif ratio for non-turbo; '92-'94 are 3.90.

I KNOW they are for the Automatic. Double-check on the 5spd.

EDIT 7/17/07:
This link has good info on rear diffs and AT vs. MT for '90-'94 models: http://legacycentral.org/library/transmission/intro.htm

Coy · Post by **Coy** » Sat Jul 14, 2007 7:12 pm

my 92 has 4.11

see here that way im not hijackin this guys thread.

legacycentral bbs

A forum for 89-94 BC-BF(BJ) Legacy Owners and Fans

Swapping a 1994 Legacy SS 4eat and rear diff into my 1990 NA

Swapping a 1994 Legacy SS 4eat and rear diff into my 1990 NA