What's required to convert a WRX from 3.9 to 4.444 final drive ratios?
 

Thanks to a tricky local hill climb I am looking for a parts shopping list to convert my stock standard ;) MY99 WRX to a final drive of 4.444

Currently it has the MY99 gearbox housing and 1-5 helical Ivan Albins gearset, (these came standard in the Glorious Nation of Kazakhstan) ;) other bits are:
[LIST][*]Original 3.9 front diff[*]Original MY99 center diff of 1.1:1 [*]Rear diff is a Kaaz 1.5 plated LSD with 3.54 crown and pinion also released in...Kazakhstan :o[/LIST]
Now a front and rear diff crown and pinion set of 4.444 seems inevitable but what's with the center diff? I guess I need one of these also? Then what about gear adapters to keep the speedo readings correct?

your speedo drive wont change (its part of your gearset), although you will probably need to change the sensor thats screwed into the speedo drive outside of the gearbox.

otherwise, all you need to change to 4.444 is to swap your crown/pinion on your main gearset (practically a complete gearbox rebuild), source a 1:1 centre diff housing (from any STI, JDM or non-turbo GC impreza). and a 4.444 rear diff.

your existing centre and rear diff centre are interchangeable.

^^ Close but not 100% accurate.

The plastic speedo drive gear inside the gearbox will require changing while the case is split, the external sensor has nothing to do with calibration.

The centre diff, viscous coupling and the transfer case remain as is, you will need 1 to 1 transfer gears from a gearbox of the same era as yours. Early 4 bolt case boxes have a different coupling spline, later ones (post ~00) have tapered bearings (yours should have ball bearings)

Also, check the gear ratios of your Albins kit as well, you may find that it's overall geared too low for 4.44's. If you have the set with a 3.45 1st and a 0.97 5th, they work best as a 4.11. If you have a 3.08 1st and a 0.87 5th get some 4.44's in it!

cool, i was never 100% sure about the sensor

yeaaahh that 0.97 5th is a killer in a 4.44 box...

Ahhh me 4k rpm at 100km/h

[QUOTE=dtrally;438992]Also, check the gear ratios of your Albins kit as well, you may find that it's overall geared too low for 4.44's. If you have the set with a 3.45 1st and a 0.97 5th, they work best as a 4.11. If you have a 3.08 1st and a 0.87 5th get some 4.44's in it![/QUOTE]
Thanks for the great info! I have a mixture of IA "Sport" 1st & 2nd (3 , 2) and IA "Street" 3rd-5th (1.36, 0.96, 0.76). As you say I need the 4.44's to liven things up for most events.

Currently with a first gear that gives up at 73km/h and a theoretical top speed of 290km/h I am not getting the best overall performance out of it.

Try to find a 99 onwards 4.44 gearbox that's broken a gear but not been driven too far afterwards. Pay up to $400 for it. If it's been 'just driven straight home' then the front crownwheel and pinion will almost certainly be chipped.
Then get someone who knows Subaru boxes to swap your gear shafts into it.
I reckon that will be easier and have a better chance of being set up correctly than playing with swapping the final drives and drop gears into your case.

What models came out post 99 with 4.44? I am thinking of fitting a Torsen front diff at the same time, probably when the clutch goes next?

If I just bought the Crown and pinion and freshened up the gear box with syncros at the same time this might be a viable option? Add drop gear and speedo adapter...rear diff also just a crown and pinion.

The guys at Neal Bates Automotive know how to build a box so I am comfortable they would get it right.

Thanks again.

[QUOTE=maddog;439532]What models came out post 99 with 4.44?[/QUOTE]

MY02-07 WRX. MY01 had the 3.9's still, so make sure its not one of those.