Can anyone help me with info on a diff swap... I have the entire rear sub-frame and diff (4.44) from a STi-5/6 type R coupe with the mechanical LSD... and I want to fit this to my WRX running STi-3 sedan running gear (3.9) Is it possible to swap out the 4.44 ratio to match the 3.9 front diff ?? I don't want to change the gearbox if I don't have to !! Thanks in advance, Mark.

 

Have you also got the rear hubs, brakes, drive shafts, etc', because you'll need those too.

You don't have to change the gearbox, but you'll need to get it stripped, and a 4.44 crown wheel, and pinion fitted, to match the back. This MUST be done by an EXPERT. If it isn't, the chances are that it won't be done right, and you'll have a nightmare, with noise, wear, etc'.

Mark.

 

Hi there,

Just to give you a bit more info on your diff swap - I own an STi version 5 type R myself, it too runs a 4:4 diff ratio.

He is right in what he says in the above reply you must run the same ratio on the rear as what is in the gear box - as all STi's run 1:1 drop gears in the gear box as standard. BUT!!!!!!!!!!
the problem you are going to have here is that the Version 5 type R rear diff housing is much larger and the only gear ratio available to fit the larger housing is 4:4. Your Sti 3:9 crown wheel and pinion will not fit the type R diff.

If you would like more information I get all my problems sorted out at Town End Garage Motorsport - www.townendgarage.co.uk I'm sure one of them would be able to explain this alot better than me and greater detail and will tell you the most simple and cheapest way to solve your problem.

Hope this helps out,

Impreza Babe.
Hope you had a Happy Christmas!!!!!

 

Thanks guys, Looks like the cheapest option (for me !) is to swap my gearbox for the matching STi-R version... second hand parts are much cheaper here (NZ) than the labour charges to rebuild a 'box !! Is there a Subaru 'box that has tall 1~5 ratios with the correct 4.44 final ?? reason for this is I do 95% motorway driving with only a few drag racing days a year... Thanks Impreza Babe ! Hope you had a good new year ;-) >Mark.

 

The '98 WRX, and 4dr STi (V4) has longer gearing (5th = 21.8mph per 1k) there may be other options too.

I'm surprised that there aren't any other options, other than the 4.44, for the R180 diff (later type R) and that they only have options for the smaller R160. Can't imagine the rally guys would be too happy with this. It would be worth asking around, because I know there are other options, other than OEM, that the rally guys use.

Mark.