2007 SG Forester XT Low Range Conversion

longy99gt · Post by **longy99gt** » Sun Sep 06, 2015 9:44 pm

Hi all,
I have been collecting pieces for a Low Range conversion into my 2007 Forester XT.

The overall plan:
SG N/A Gearbox - SF 1.4 Low Range - 4.11 FDR - XT Gearset (3,4,5th)

What I have collected:
1x Half 2006 SG N/A Gearbox (opened but no centre diff)
1x Full 2006 SG N/A Gearbox and matching 4.11 Rear Diff
1x Full 2006 GD WRX Gearbox (blown Synchro's)
1x KAAZ front 1.5 way clutch type LSD
Interior Centre console and cable linkages for low range lever

What i still need:
HD Clutch to suit NA gearbox
Clutch Slave cylinder to match N/A Gearbox
Gearbox and diff oils

The Final Product:
I will be using the SG case, with 1sr and second gear from the SG N/A box,
then switching out 3/4/5 from the WRX (Same as the XT) so i have taller gears, which will be good for highway work, and keeping the 4.11 Final Drive Ratio which will give me lower RPM when at 110kmh,
with a lightly tuned turbo motor, and future addition of an exhuast upgrade, power will be no issue and it should be sitting on around 2650RPM when doing 110kmh~ (instead of 2950 which seems overkill when the car's empty..)
I am also swapping the lowrange from 1.19 (SG) to 1.4 (SF) to make the reduction somewhat worthwhile.
also going in is a KAAZ 1.5Way Front Clutch Type LSD (one of the only types that still work with a lifted wheel)

In the future when the finances recover i may look to add a rear LSD to replace the useless VLSD.

Stay Tuned for the install and pics! should be hopefully happening over the next month, interior is installed ready with the lever, so i can atleast pretend i have low range for now.

Longy

vincentvega · Post by **vincentvega** » Mon Sep 07, 2015 9:30 am

sounds like a great gearbox combo. I am interested to see how you go with it.

Be careful with gearing too tall. You might find yourself dropping back to 4th more often on the highway, especially when cruising at 100kph

Venom · Post by **Venom** » Mon Sep 07, 2015 4:49 pm

When I did my last dual range build for the Liberty I went with the taller 5th to have the revs sit at around 2500 rpm, my thinking been that is that it's closer to where the auto sits in 4th. Made no difference to my fuel consumption that I could notice and it dropped the motor out of it's power band. With the stock SF gearbox I swapped in recently it's sitting on nearly 3000rpm at 100 and still using 10l/per 100km, and it's ready to boogie when I put the foot down. So I'm not convinced dropping the revs in 5th actually does a lot for fuel economy.

I'll be doing a similar build to you soon (ish), keeping all of the stock SG gearing 1 - 5, putting in a 4.44 to compensate for slightly larger tyres and that's it for gearing. Keeps it relatively simple.

Your final tyre size is probably the biggest determining factor for what gearing will work best.

I'd recommend going on the hunt for a 5MT DCCD, swap out the DCCD and then on sell it as a standard STI gearbox. It'll do more for you than the front diff, but ideally you'd have a good diff front centre and rear.

longy99gt · Post by **longy99gt** » Mon Sep 07, 2015 5:57 pm

as its a 2.5L Turbo with a mild tune, and a future Low resistance TBE exhuast will be added, i dont believe i will have any problems sitting at 2650 at 110kmh,
i am using 215/65/16 tires, so they aren't huge, just slightly bigger than the stock 215/60/16
i think that if the car is loaded fully and its a reasonable hill, it'll probly need dropping back to 4th to get up easily, but for all other cruising with a medium-light load, it'll be fine, and i am just on the bottom of the torque curve,

currently i am using 8-9L/100K with a light load, on the highway,
and around 10L/100K with a medium load or light trailer, sometimes upto 11 in head winds of very hilly areas with a heavy car.
thats since getting the tune done, has made good fuel saving differences,
I have an accurate Ultragauge so i can monitor the difference before and after.
it was sitting closer to 11-12L/100K with a loaded car on the highway.
if it wasnt turbo then i would probably stick with shorter gears.

longy99gt · Post by **longy99gt** » Mon Sep 07, 2015 6:03 pm

as for DCCD, its in the Centre and just makes sure power goes to front and back,
main problem is diagonal wheel spin, and the centre has no control over this,
so dropping in a front LSD thats a clutch type will always give power to both front wheels and atleast one rear wheel, getting rid of diagonal wheel spin.
as good as DCCD is, you still have diagonal spin, which doesnt help offroad in undultaing terrain, its great for track and rally work though and wheels and basically always in contact with the ground, just with varying levels of traction

vincentvega · Post by **vincentvega** » Tue Sep 08, 2015 9:19 am

i found the same thing as venom with gearing.

When I converted from 4.44 auto to 3.9 manual I went from 2500rpm at 100kph to about 2900rpm at 100. I actually use less fuel now (but i put some of that down to the manual conversion) and have way better driveability as the motor is in its power band. I just leave it in 5th and it pulls up anything.

NA EJ22 though. Your 2.5L turbo could well be different.

vincentvega · Post by **vincentvega** » Tue Sep 08, 2015 9:21 am

and on diagonal wheel spin I also have a VLSD rear and my technique has always been to keep the boot in for a few extra seconds once i lose traction. most of the time i can feel the rear end tighten up and the car continues forward.

VLSD needs to build up heat to lock up. Sounds like mega abuse but i have put about 150K on this diff center without issue.

NachaLuva · Post by **NachaLuva** » Sun Sep 13, 2015 3:33 pm

I agree that the front diff is the most important, unfortunately its also the most difficult. But don't underestimate a good centre diff, thats why the L series with their locking centres do so well. While you're doing the box, I reckon a DCCD is a good idea, although it can be swapped in later without dropping the box.

I like what you're doing with the gears, pretty much what I'll be doing.

longy99gt · Post by **longy99gt** » Mon Sep 14, 2015 6:21 pm

Vincent,
if you are still moving a lil, then booting it will get VLSD to help and hopefully stock you from getting stuck, however, this isnt always an option depending on the terrain,
for instances climbing slowly up a hill, or if you stop on a hill thats rutted, then VLSD cant help, and thats where the benefit of the Front LSD comes in, well atleast the clutch type front LSD anyway.

as for the locking Centre diff in the L series/Brumby, isnt that still only locking power front/back, they still have open front/rear diffs?
it will just guarantee you have front/back power from the get go, instead of it needing the viscous centre diff coupling to do it like the AWD cars are,
ideally DCCD + F LSD + R LSD, but we only have so much money,
i think i'll still keep the rear VLSD anyway, it just wont be contributing on the slower climbs
Now i am just on the search for a Gearbox specialist to piece it together,

vincentvega · Post by **vincentvega** » Mon Sep 14, 2015 6:59 pm

i am specifically talking about slow climbs. if i get to a point where i am no longer moving forward and have diagonal wheelspin i keep the boot in and most times the rear end locks up and i move forward.

if that doesnt happen i ease the brakes on to control the wheelspin then back down for another go at it.

i am not talking about full noise wheelspin here. just keeping whatever throttle you were using on for a few seconds after losing momentum. works more times than it doesnt for me.