Tomi's '99 JDM S15 Silvia

[SR2O 1]

Dropped out of the scene for a bit (building a house), so haven't had much time for the S15 recently. However since my last update, have done the following:

 

- R33 GT-R diff which has a 4.11 ratio (37:9)

- R33 GT-R half-shafts which are 6-bolt with thicker splines and more teeth

- R33 GT-R axles, again thicker and 6-bolt

- R33 GT-R hubs to suit the above setup

 

The above components were installed for two primary reasons 1) to gain a better 4.11 ratio and 2) to gain the stronger (thicker) 6-bolt half shafts and axles from the R33 GT-R. Now on paper this may seem like a pretty straight forward conversion, however this is not a direct bolt if you want to retain your ABS system and/or speedo reading. Here are the reasons why:

 

- The S15 diff (R200) uses a 3 channel ABS system (meaning one sensor for each front wheel, and a single sensor for both rear wheels). The sensor on the diff not only provides the ABS module with a signal (sine-wave) but also provides the VSS (vechile speed signal) to the speedo. The sensor pickup is mounted on the front (pinion) of the diff and has a single ABS harness plug.

 

- The R33 GT-R diff (R200) uses a 4 channel ABS system (meaning one sensor for each wheel). The diff itself has two sensors, these read sprokets on either side of the half shafts which then merge into a single ABS harness plug. Mechanicaly, the way in which the ABS signal is being determined is different to the standard S15 system. Because of this you cannot just 'plug and play' as the signal pulse will be different to what the ABS module\speedo in the S15 has been configured for.

 

So after much research there are really only three options for this situation:

 

1. Forget about your S15 having ABS and/or a speedo reading. If this doesn't bother you then the R33 GT-R diff, half-shafts, axles and hubs will all bolt up directly to an S15 subframe. You must have all of these components for it to work.

 

2. Create a custom ABS sensor pickup that replicates the standard S15 setup, i.e. this would involve retrofitting a custom sproket (which replicates the diameter and teeth of the stock pickup) to the tailshaft, which can then be read by a sensor

 

3. Transplant the R33 GT-R diff centre and half shafts into a R33 GTS-t diff (R200, with 4.11 ratio and pinion mounted ABS sensor, like the S15). With this approach the R33 GTS-t crown and pinion is used on the R33 GT-R diff centre. BBy doing this you are able to achieve a 4.11 diff ratio, gain the stronger 6 bolt half shafts and axles, retain ABS and speedo readings. This is the option I went with as I was able to get a R33 GTS-t housing for free to attempt this transplant.

 

In hindsight, the easiest way to do this conversion (if only for the 4.11 ratio) is to go with a R33 GTS-t (Series II, manual) diff - however note the downside is that the half-shafts\axles are a 5-bolt not the 6-bolt like the GT-R.

 

Hope that helps anyone considering this, information on the Internet is very fragmented I have done my best to bring this together. If anyone needs more specific details around this then feel free to PM me.

Edited September 21, 2012 by SR2O

[SR2O 1]

Also one other point I forgot to mention - because the diff ratio is being changed so does the pulse that the signal produces. This means that your speedo reading will be slightly out and need to be calibrated by a speedo signal modulator - heaps are available online, or even kits through JayCar Electronics to do this.

[SR2O 1]

For those interested, here's a couple of pictures of the GT-R items post cleanup and transplant into GTS-t housing and final installation. Also fitted a GKtech billet diff cover (baffled w/extra 900cc)

 

[JDM Driftjunkie 0]

just went through this whole thread and this car is amazing im so keen to get an s15 now in white i love it