Jump to content
SAU Community

Recommended Posts

I've been thinking about the best way to go for an RB25 upgrade for my R32. I don't want to be ripped off or dissappointed so I'm just wondering...

What's the best way to go with an RB25 upgrade and what should I be paying for one?

An estimate price for a stuffed engine that needs rebuilding would be great and maybe a price for a low km engine that can go straight i would be awesome.

James

just keep an eye on the for sale section, also call around the jap wreckers to see what they charge for a complete engine to give yourself something to reference to.

http://www.skylinesaustralia.com/forums/topic/358328-real-deal-rb25-setup/page__p__5725529__hl__rb25__fromsearch__1#entry5725529

just keep an eye on the for sale section, also call around the jap wreckers to see what they charge for a complete engine to give yourself something to reference to.

http://www.skylinesa..._1#entry5725529

So his rebuilt, forged engine is going for $1700 and his rebuilt gearbox is going for $1500 and the only other things i'll need are a computer and loom.

Not too shabby. Just depends whether its worth it or not. If I can get my 32 to 300rwkw for roughly the same I won't bother aha.

You got a conversion in yours?

yea, mine has a rb25 with a gt3076. In all honesty though, i feel the turbo is a little laggy for my liking. I may end up down sizing the turbo at some stage, or maybe just hunt down an externally gated .63 housing for it.

That link was just an example, I'm not saying to buy it, I'm pretty sure I saw a a complete rb25 long motor for sale either here or boost cruising the other day for 1200, you would expect to pay anywhere from 1000-2000 for a decent condition engine. Totally worth while to have the extra cubes down low as well, much nicer to drive off boost then an rb20

yea, mine has a rb25 with a gt3076. In all honesty though, i feel the turbo is a little laggy for my liking. I may end up down sizing the turbo at some stage, or maybe just hunt down an externally gated .63 housing for it.

That link was just an example, I'm not saying to buy it, I'm pretty sure I saw a a complete rb25 long motor for sale either here or boost cruising the other day for 1200, you would expect to pay anywhere from 1000-2000 for a decent condition engine. Totally worth while to have the extra cubes down low as well, much nicer to drive off boost then an rb20

Ahhhhh I see. I had no idea they're so cheap!!! I might have to do this hey. I think it'll all be in the compressor housing dude or yeah if its more than that just research the best combination for the 25.

If I've got a lightened fly and HD clutch, will an rb20 gearbox cope with an rb25?

Edited by EXEMPT

Ahhhhh I see. I had no idea they're so cheap!!! I might have to do this hey. I think it'll all be in the compressor housing dude or yeah if its more than that just research the best combination for the 25.

If I've got a lightened fly and HD clutch, will an rb20 gearbox cope with an rb25?

Depends how you drive but likely not. I killed a couple of RB20 boxes with only 183rwkw, first one behind the RB20, second behind the RB30 (the second one died real quick.. I don't think it liked so many 2nd gear clutch drops :laugh: )

Depends how you drive but likely not. I killed a couple of RB20 boxes with only 183rwkw, first one behind the RB20, second behind the RB30 (the second one died real quick.. I don't think it liked so many 2nd gear clutch drops :laugh: )

I might have to get someone to look at my gearbox coz im pushing a fair bit more than that atm. Gearbox feels solid as all hell but I mean Murphys Law will come into play as soon as the rb25 goes in, if it does lol.

Cool. I'll have my mechanic confirm I've got an rb20 gearbox next Friday.

Is there anything that is obviously different on the outside of the two boxes that will indicate 20 or 25 box? I'm only asking because the car runs 230rwkw on 20 psi and has done for a long long timeand hasn't complained at all. Only when I le the clutch out before I complete the shift pinch.gif

Is it torque or power from the engine that wears a gearbox?

Edited by EXEMPT

Torque, power is just a function of torque and revs (and a constant).

Physically, the RB25 is SHITLOADS bigger than the RB20 box. If you have a look down the transmission tunnel and the gearbox barely fits.. it's probably an RB25 box. Couple of other things like how the slave cylinder bolts on and the speedo sender is one the bottom of the output shaft on one box, and on the top on the other.. can't remember which way round it is though..

If you need me to, send me a PM and I'll have a look under the car when I get home :)

Torque, power is just a function of torque and revs (and a constant).

Physically, the RB25 is SHITLOADS bigger than the RB20 box. If you have a look down the transmission tunnel and the gearbox barely fits.. it's probably an RB25 box. Couple of other things like how the slave cylinder bolts on and the speedo sender is one the bottom of the output shaft on one box, and on the top on the other.. can't remember which way round it is though..

If you need me to, send me a PM and I'll have a look under the car when I get home :)

Noo shit. Well that should be a fairly easy diagnosis then =) I'll be sure to check it out when I'm home in a coupla hours. If I can't make my own mind up I'll snap a pic and post it up lol.

Cheers dude.

heres how you tell which box you've got;

RB25 box on the left, RB20 box on the right.

post-13452-0-26397000-1300858744_thumb.jpg

you can tell the difference straight away. the rb20 box is noticeably smaller and it has some differences in the housing.

in your case, buy a half cut - it will be much cheaper than buying everything separately. it should cost you around $3000-$3500. i also recommend doing a leak-down and compression test before anything. if the motor is in good nik then the gearbox that is attached is more than likely to be in good nik, i.e. not abused.

heres how you tell which box you've got;

RB25 box on the left, RB20 box on the right.

post-13452-0-26397000-1300858744_thumb.jpg

you can tell the difference straight away. the rb20 box is noticeably smaller and it has some differences in the housing.

in your case, buy a half cut - it will be much cheaper than buying everything separately. it should cost you around $3000-$3500. i also recommend doing a leak-down and compression test before anything. if the motor is in good nik then the gearbox that is attached is more than likely to be in good nik, i.e. not abused.

Very nice bro thanks for your wise words also! I can see this happening in the months to come aha

Definitely buy a half cut if you don't already have a 25 box in there. People over here want $1500ish for the gearbox alone. I then had a custom 2-piece shaft made up (to handle huge torque), that along with a new slave cylinder and some miscellaneous stuff, brought the gearbox conversion to around $2500 and that's with me doing all the labour.

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

    • For DBA, check out their guide table here. https://dba.com.au/wp-content/uploads/2023/01/Direct_Replacement-Guide-2021.2.pdf   Additionally they have some other guides and info on how to make sure you choose the right pad.
    • Sorry, just assumed that talk of coloured pads meant EBC red/green/yellow/shit stuff. I don't know the DBA pads, but it's a reasonable bet that they will be OK. DBA make good stuff generally. Those 4000 series rotors I linked to are very good. I may well replace the RDA rotors I have with those when required.
    • The average previous owner for these cars were basically S-chassis owners in the US. Teenagers or teenager-adjacent. I often tell people that neglect is easier to fix than something that was actively "repaired" by previous owners.
    • Update 3: Hi all It's been a while. Quite a lot of things happened in the meantime, among other things the car is (almost) back together and ready to be started again. Things that I fixed or changed: Full turbo removal, fitting back the OEM turbo oil hardlines. Had to do quite a bit of research and parts shopping to get every last piece that I need and make it work with the GT2860 turbos, but it does work and is not hard to do. Proves that the previous owner(s) just did not want to. While I was there I set the preload for the wastegates to 0,9bar to hopefully make it easier for the tuner to hit the 370hp I need for the legal inspections that will follow later on. Boost can always go up if necessary. Fitted a AN10 line from the catch can to the intake hose to make the catchcan and hopefully the cam covers a slight vacuum to have less restrictive oil returns from the head and not have mud build up as harshly in the lines and catch can. Removed the entire front interior just shy of the dashboard itself to clean up some of the absolutely horrendous wiring, (hopefully) fix the bumpy tacho and put in LED bulbs while I was there. Also put in bulbs where there was none before, like the airbag one. I also used that chance to remove the LED rpm gauge on the steering column, which was also wired in absolute horror show fashion. Moved the 4in1 Prosport gauge from sitting in front of the OEM oil pressure gauge to the center console vents, I used a 3D printed vent piece to hold that gauge there. The HKB steering wheel boss was likely on incorrectly as I sometimes noticed the indicator reset being uneven for left vs. right. In the meantime also installed an airbag delete resistor, as one should. Installed Cube Speed premium short shifter. Feels pretty nice, hope it'll work great too when I actually get to drive. Also put on a fancy Dragon Ball shift knob, cause why not. My buddy was kind enough to weld the rust hole in the back, it was basically rusted through in the lowermost corner of the passenger side trunk area where the wheel arch, trunk panel and rear quarter all meet. Obviously there is still a lot of crustiness in various areas but as long as it's not rusted out I'll just treat and isolate the corrosion and pretend it's not there. Also had to put down a new ground wire for the rear subframe as the original one was BARELY there. Probably a bit controversial depending on who you ask about this... but I ended up just covering the crack in the side of the engine block, the one above the oil feed, with JB Weld. I used a generous amount and roughed up the whole area with a Dremel before, so I hope this will hold the coolant where it should be for the foreseeable future. Did a cam cover gasket job as the half moons were a bit leaky, and there too one could see the people who worked on this car before me were absolute tools. The same half moons were probably used like 3 times without even cleaning the old RTV off. Dremeled out the inside of the flange where the turbine housing mates onto the exhaust manifolds so the diameter matches, as the OEM exhaust manifolds are even narrower than the turbine housings as we all know. Even if this doesn't do much, I had them out anyways, so can't harm. Ideally one would port-match both the turbo and the manifold to the gasket size but I really didn't feel up to disassembling the turbine housings. Wrapped turbo outlet dumps in heat wrap band. Will do the frontpipe again as well as now the oil leak which promted me to tear apart half the engine in the first place is hopefully fixed. Fitted an ATI super damper to get rid of the worn old harmonic balancer. Surely one of the easiest and most worth to do mods. But torquing that ARP bolt to spec was a bitch without being able to lock the flywheel. Did some minor adjustments in the ECU tables to change some things I didn't like, like the launch control that was ALWAYS active. Treated rusty spots and surface corrosion on places I could get to and on many spots under the car, not pretty or ideal but good enough for now. Removed the N1 rear spats and the carbon surrounding for the tailpipe to put them back on with new adhesive as the old one was lifting in many spots, not pretty. Took out the passenger rear lamp housing... what do you know. Amateur work screwed me again here as they were glued in hard and removing it took a lot of force, so I broke one of the housing bolts off. And when removing the adhesive from the chassis the paint came right off too. Thankfully all the damaged area won't be visible later, but whoever did the very limited bodywork on this car needs to have their limbs chopped off piece by piece.   Quite a list if I do say so myself, but a lot of time was spent just discovering new shit that is wrong with the car and finding a solution or parts to fix it. My last problem that I now have the headache of dealing with is that the exhaust studs on the turbo outlets are M10x1.25 threaded, but the previous owner already put on regular M10 nuts so the threads are... weird. I only found this out the hard way. So now I will just try if I can in any way fit the front pipe regardless, if not I'll have to redo the studs with the turbos installed. Lesson learned for the future: Redo ALL studs you put your hands on, especially if they are old and the previous owners were inept maniacs. Thanks for reading if you did, will update when the engine runs again. Hope nothing breaks or leaks and I can do a test drive.
×
×
  • Create New...