Another great Forester project with STi 6 speed swap installation and Spiider Plus DCCD controller:
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2008+ STi 6 Speed Trans Swap Guide
LIST OF NEEDED PARTS TO SWAP A MY’08 6 SPEED INTO A WRX
-04 to 07 are direct fit
-08 can be used – it must be shortened (read below)
Axle stubs, seals, and circlips to reuse your front wrx axles
-can also use 04 to 07 STi axles if you have the supporting hubs*** – 08 axles are too long i believe
6 speed clutch, flywheel, and fork
– 5 speed clutch and flywheel will NOT work
Can reuse all the rear end driveline if it is a wrx with a 3.54 rear end (02 to 04?) i believe
– If 05 wrx and up (other than 3.54 rear) you will either need to:
– swap to a 3.54 rear diff
– swap out your ring and pinion
– swap to the sti (06? and up) rear end (3.54)
– this one will require in the rear the sti axles, hubs, brembos, and rear sti suspension assy
Linkage form an 04 to 07 sti – this is the easiest – buy one
– the 08 one may be able to made fit but it will require extensive shortening and *may* throw off your shifter position – don’t be cheap
08 trans mount and support works just fine
slave cylinder and starter can be reused
1. What are the diff ratios in the 08+ transmissions?
The diff ratios are unchanged from 2007 It runs a 3.90 in the front and a 3.54 in the rear which yields a 1.1 center. Strait swap into the bugeye wrx if you don’t plan to swap the rear diff right away.
2. Are there any changes to the gear ratios from 07?
The ratios appear to be the same.
3. Are there any changes to the housing or overall case size?
No it is still the same overall size as previous years.
4. Are there any changes to the wheelbase length in 08 to affect the driveshaft length?
Yes – 02 to 07 the wheelbase length is 100 inches. In 2008 it was LENGTHENED to 103.3 inches. This will explain why MY02 wrx 5 speed and the 08 sti driveshaft are the same IDENTICAL length when laid next to each other. The 08 sti driveshaft can be made to work – it needs to be shortened.
5. Can an 04 to 07 sti driveshaft be used with an 08 sti tranny?
Yes – you will need to find a driveshaft from an 04 to 07 sti or from an automatic impreza.
Note: The 08 driveshaft can be shortened and made to fit. If you decide to shorten your 08 STi driveshaft –
the front half must be shortened 3 inches and the back half must be shortened 0.5 inches
You must also modify the center bearing bracket cause it is a slightly different shape in 08. the drivers side of the bracket must be “bent” so that it is higher than the passenger side – if you look at the mounting holes you will understand. in 08 the center-bearing bracket is nearly flat.
6. Can the 08 shifter assembly be used in an earlier model when doing a swap?
No – The shifter linkage along with the brace bar underneath are too long. It seems that the hole cut under the center colsole for the shifter assy has been moved backwards in 08 to cause the linkages to be longer. You will need an STi shifter assemblyy from an 04 to 07.
7. When doing a swap to a wrx with female front axles, can the same axle stubs and seals be used as if it was an 07 trans?
Yes – Install the seals and stubs with circlips in the trans.
805329010 – Circlips x2
38415AA110 – Stubs – x2
806730041 – Oil seal left
806730042 – Oil seal right
633046020 – Spring pin x2
8. Are there any changes to the trans fluid and rear diff fluids needed?
No – Use valvoline 80w90 in the trans and the house blend subaru LSD oil in the rear diff.
9. The 08 trans does ont have a dipstick anymore?
True – there is a plug where the dipstick should be. the filling process is to open both plugs underneath and let it drain completely, then fill is with the specified amount of oil – After 7 qts you see the level in the hole with a light and it was still about 4 to 5 inches below the hole! There is a second plug on the driver side of the trans near the front that when it is opened and 4.5 qts is poured in, the oil level will be level with this hole. There is an illustration in the link below.
10. The 08 trans does not have a speed sensor anymore
vsspro which will wire into an abs sensor and output a use-able signal for the speedometer. It will comes with a potentiometer which will be able to adjust the signal output to accommodate different size wheels.
11. The 08 transmission DCCD
If you want to take full advantage of your swapped in STi transmission then a Spiider DCCD Controller is recommeneded.
Win with Spiider Plus
Great news! Amanda Skelly Comes second in 2018 Eastern RallySprint Series (2nd Overall Driver and 2nd in AWD catagory)! We are proud to be a small part of this success with our Spiider Plus DCCD Controller.