Jump to content
SAU Community

Recommended Posts

Basically I have bought an series 2 RB25DET 4wd from a Stagea

Just wondering if leaving the front diff from the stagea with the rest of the driveline being standard gts4 would the attesa system still work fine with the different diff ratios (if there is any? presuming that their is, stagea was auto btw)

Also, if anyone who has done this conversion could you tell me what else will need changing? will be putting 25det loom and ecu in, manifold and external wastegate on, and a front mount intercooler on at the same time. So should be a good improvement over the standard rb20det

Thanks in advance

Cheers

Link to comment
https://www.sau.com.au/forums/topic/242104-r32-gts-4-rb25det-conversion/
Share on other sites

It's a different ratio (4.083 v 4.375). Therefore the rears will be turning faster than the fronts, causing the ATTESSA to activate drive to the fronts, and the the front will want to accelerate away from the rear. Not a good idea.

I would recommend you get hold of a Stagea rear diff assembly and have the crown wheel and pinion swapped over into the GTS4's centre and housing. (The torque out of the RB25 doesn't justify the 4.375 ratios)

You see, I read all these things. I know the diff ratios are diff from 32 and 33. Icontinue seeing these threads pile up with the same information.

But when I did my conversion. The ratio's were the same. I dropped in a DE which may have been the diffrence. Lower gear ratios for a less powerfull engine. Makes sence.

But yes, the easiest way to do it is as Elk said. swap the wheel and pinion over.

Or get a 4.375 rear diff. The 32 gearing is ver short as it is, depending on what your planning to do with the car you may find it a better option to change to a larger diff ratio.

Edited by GTS4WD
You see, I read all these things. I know the diff ratios are diff from 32 and 33. Icontinue seeing these threads pile up with the same information.

But when I did my conversion. The ratio's were the same. I dropped in a DE which may have been the diffrence. Lower gear ratios for a less powerfull engine. Makes sence.

But yes, the easiest way to do it is as Elk said. swap the wheel and pinion over.

Or get a 4.375 rear diff. The 32 gearing is ver short as it is, depending on what your planning to do with the car you may find it a better option to change to a larger diff ratio.

No, the R32 already has 4.375 rear diff ratio (and a 4.375 front diff ratio). The Stagea has 4.083 (@ both ends!)

There are 2 options:

1. Swap the front diff from the RB20 into the RB25, so you retain the factory R32 4.375 ratio.

2. Swap the C/W and Pinion from a Stagea REAR diff onto the diff centre of the R32 REAR diff (the Stagea seems to run an "open" rear diff, not a Viscous Coupled rear diff like the R32). This way, you get the Stagea 4.083 ratios.

With the torque of the RB25DET, I would go for option 2 while you have the opportunity and everything is out of the car. (Because I've been there, done that)

With option 2, you will need to change the speedo drive gear in the gearbox to a R32 GT-R unit, to keep the speedo readings correct.

Ok sweet thanks, does anything else run the 4.083 rear diff ratio that will still fit upto 4wd driveline?

and if i went with option 1 (rb20 front diff) what sort of rpm would the car be sitting at at 100kph in 5th gear (currently about 2900rpm, pretty high for a 2ltre i think)

will eventually want to put a gtr driveline in it at some stage, not at this point in time though, want to get it back on the asap now.

also, my right front CV joint is f**ked, what CV joints do they take?

thanks for your help, good to see a few GTS4 owners on here aswell :(

Ok sweet thanks, does anything else run the 4.083 rear diff ratio that will still fit upto 4wd driveline?
Not that I'm aware of.
and if i went with option 1 (rb20 front diff) what sort of rpm would the car be sitting at at 100kph in 5th gear (currently about 2900rpm, pretty high for a 2ltre i think)
Should be exactly the same because you'd still have the factory driveline.

in mine with stagea RB25 and box and GTS-4 diffs it revs at around 2880rpm at 100km/h and 3060rpm at 110km/h dosen't feel like the engine is revving its tits off (its a pig on fuel anyway so fuel consumption remains at around 18l/100)

Edited by bozodos
Ohh and also, to swap the diffs over, do you need to swap the whole sump or can u take just the diff off buy itself?
You can swap just the diff itself. You MUST swap both the Crown Wheel and the Pinion - they are a matched set. Have fun undoing the pinion retaining nut!

Hey guys, i have a r32 gts4 with a stagea rb25 conversion. I had a work shop do the conversion and they had a few issues, one of which was the trying to attach the rb 20 front diff/sump to the block (rb25) eventually they ended up machine the bottom of the block to fix the front diff axial across the bottom of the sump. I am pretty sure, thats what they did. and now if i am full lock or accelerate quickly i get 50/50 touque split which i assume is from the rb20 rear diff and the rb25 front diff! umm thats a bad thing........oh shit~

You can swap just the diff itself. You MUST swap both the Crown Wheel and the Pinion - they are a matched set. Have fun undoing the pinion retaining nut!

ok sweet, so how is the diff attached to the sump? i thought they were one piece, so ur saying the rb20det front diff will just bolt upto the rb25det sump?

Remove the cover plate off the diff housing, remove the drive shafts, and the diff centre basically falls out. To undo the pinion nut, lock out the flange against the block with something like a cold chisel, then use a BIIIGGGG breaker bar to get the leverage to undo the nut. The pinion comes out the same direction as the centre.

  • 2 weeks later...

Use GTS4 rb20det sump & diff and bolt that on your stagea rb25det motor. It bolts straight up. Done it before. RB20det 4wd ratio's are shorter and more fun. Hence alot of GTR's convert to GTS4 ratio's

Also listen to blind elk. he knows what he's talking about and helped me ALOT via PM's last year, while doing this very same conversion

Use GTS4 rb20det sump & diff and bolt that on your stagea rb25det motor. It bolts straight up. Done it before. RB20det 4wd ratio's are shorter and more fun. Hence alot of GTR's convert to GTS4 ratio's

ok sweet, bolting the rb20det sump and diff on sounds a whole lot easier if it just straight bolts up. any probems with running rb20det sumper coz maybe be smaller or anything silly like that. lol soz bout all the n00b questions but im learning :P

Cheers guys :laugh:

  • 5 weeks later...

i have heard both.... that it is a same bolt on but i can tell u, some of them dont! i had it done at opition one auto and they showed me the difference between the two sumps! hey i had to have the block machined

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


  • Similar Content

  • Latest Posts

    • Even more fun, leave all the ADAS stuff plugged in, but in different locations, hopefully avoid any codes!   And honestly, all these new cars with their weird electronics. Pull all the electronics out Duncan, and just shove an aftermarket ECU and if needed a trans controller in, along with a PDM. Make it run basic but race car styled!
    • To follow up a question from earlier too since I had the front bar off again (fking!) This is what is between the bumper and the drivers side wheel And this is the navigator side, only one thing but its a biggy! So basically....no putting coolers in the wheel arches without a lot of moving other stuff. Assuming I move to properly race prepping this car I'll take that job on and see how the computers respond to removing a whole bunch of ADAS modules
    • So I prepped the car for another track day on Wednesday (will be interesting to see coolant temps post flushing out and the larger reservoir, with a forecast of 3-14 being 20o cooler than last time I took it out). Couple of things to mention; since I am just driving the car and not taking a support vehicle, I took the rear seats out and just loaded the back up Team Trackday style. Look at all that space! To cover off removing the rear seat....it is weird (note the hybrid is probably different because it wouldn't have folding rear seats) Basically, you remove the lower seat base, very similar to a r series but it is a clip that pulls forward to release the base rather than it being bolted down. Easy Then, you need to remove the side section of the rear seat on each side. There is a 14mm head nut at the bottom of the side piece, the it slides upwards off a hook at the top to release; you also need to unhook the seatbelt from the loop at the top. Then the centre piece is weird. You need to release/fold the seats forward with the tab in the boot on each side From there, there are 2,x12mm headed bolts holding the rear of each seat to the folding bracket, under the trim between the rear seat and the boot (4x christmas tree clips there, they suck). The seat is out but you can see where the bolts attach to the bracket
    • As discussed in the previous post, the bushes in the 110 needed replacing. I took this opportunity to replace the castor bushes, the front lower control arm, lower the car and get the alignment dialled in with new tyres. I took it down to Alignment Motorsports on the GC to get this work done and also get more out of the Shockworks as I felt like I wasn't getting the full use out of them.  To cut a very long story short, it ended up being the case the passenger side castor arm wouldn't accept the brand new bush as the sleeve had worn badly enough to the point you could push the new bush in by hand and completely through. Trying a pair of TRD bushes didn't fix the issue either (I had originally gone with Hardrace bushes). We needed to urgently source another castor arm, and thankfully this was sourced and the guys at the shop worked on my car until 7pm on a Saturday to get everything done. The car rides a lot nicer now with the suspension dialled in properly. Lowered the car a little as well to suit the lower profile front tyres, and just bring the car down generally. Eternally thankful for the guys down at the shop to get the car sorted, we both pulled big favours from our contacts to get it done on the Saturday.  Also plugged in the new Stedi foglights into the S15, and even from a quick test in the garage I'm keen to see how they look out on the road. I had some concerns about the length of the LED body and whether it'd fit in the foglight housing but it's fine.  I've got a small window coming up next month where I'll likely get a little paint work done on the 110 to remove the rear wing, add a boot wing and roof wing, get the side skirt fixed up and colour match the little panel on the tail lights so that I can install some badges that I've kept in storage. I'm also tempted to put in a new pair of headlights on the 110.  Until then, here's some more pictures from Easter this year. 
    • I would put a fuel pressure gauge between the filter and the fuel rail, see if it's maintaining good fuel pressure at idle going up to the point when it stalls. Do you see any strange behavior in commanded fuel leading up to the point when it stalls? You might have to start going through the service manual and doing a long list of sensor tests if it's not the fuel system for whatever reason.
×
×
  • Create New...