Jump to content
SAU Community

Recommended Posts

hey, due to all my turbo probs lately I've decided that I'm going to swap out my engine. I'm just going to replace it with a second hand one for the moment and slowly rebuild my current engine with much stronger gear. thinking an RB26 crank and con rods forged pistons bigger cams etc. i know i could just drop a 26 in but its more about the experience of building something up. i know it would cost around the same if not more in the long run but after allot of though it's what i want to do.

my only question is the gear box. i'm interested if an RB26 gearbox can bolt to an RB20 engine. as i want a box that could handle a bit more punishment. Plus something with a different gear ratio to the standard RB20 box. any one know if one will bolt up or not?

The RB26 box is not of any use to you because of the 4WD transfer case hanging off the side of it.

An RB25DET gearbox is the same but without the 4WD gear, and yes they bolt on.

Oh yeah, you'll need to have a custom tailshaft made up because the 25 gearbox is bigger.

I'd just leave the box you have until you have the power to require changing to a stronger box.

Edited by Bluprint
The RB26 box is not of any use to you because of the 4WD transfer case hanging off the side of it.

An RB25DET gearbox is the same but without the 4WD gear, and yes they bolt on.

Oh yeah, you'll need to have a custom tailshaft made up because the 25 gearbox is bigger.

I'd just leave the box you have until you have the power to require changing to a stronger box.

I'll be ordering my replacement engine soon, and i just figured i was better off to get the gearbox at the same time!

although i would be interested to know if the rb25 gearbox has sincro in 1st as the rb20 gearbox doesn't and it really ticks me off sometimes.

Edited by Viper_r32
I'll be ordering my replacement engine soon, and i just figured i was better off to get the gearbox at the same time!

although i would be interested to know if the rb25 gearbox has sincro in 1st as the rb20 gearbox doesn't and it really ticks me off sometimes.

All Nissan boxes since at least the 60's have had synchromesh on all forward gears.

Edited by mjfawke
All Nissan boxes since at least the 60's have had synchromesh on all forward gears.

not true as all s13, boxes and rb20 boxes do not contain sincro in first gear,

this is why when you slow down at a set of light and just as your about to stop the lights turn green so you go to stick the gear in first but the box wont let you. this is because 1st dose not contain sincro!

not true as all s13, boxes and rb20 boxes do not contain sincro in first gear,

this is why when you slow down at a set of light and just as your about to stop the lights turn green so you go to stick the gear in first but the box wont let you. this is because 1st dose not contain sincro!

+1 for GTR boxes not having first gear syncro

Im pretty sure the first 5 speed GTRs had the same 5 speed thats used behind the RB25, in fact arn't they rated as a stronger box than the 6 speed anyways? Just going off rumours etc but i know the 25 box is strong as anyways and bolts on, so it would probly be your best bet. Cheaper too maybe?

geese when did this turn into a debate, i hate debates :)

cant we all just get along :(

anyway i know my gearbox and the one my mate has in his s15 do not have sincro in first, so would prefer one that dose. so maybe a 25 box is the go, I'll see what the price difference is when i order my replacement RB20.

decided that I'm just getting a replacement RB20 for now. but im going to replace the watter and oil pump for N1 stuff. and put one of those new stronger collars on the pump as i believe thats what has caused the prob in my existing engine.

so wile I'm getting that done i'm going ahead with a short shifter kit, and replacing my Cusco coil overs for some Tien Super Street ones. as the Cusco are just to stiff for a daily driver. I'm getting new bucket seats. a clear camgear cover and to top it all off a new shift knob

so about $5000, later but that's the price you pay for high performance cars!

and ill just keep my existing engine and slowly rebuild it over time, possibly a full Tomei RB22 or 24 kit. well see........

Edited by Viper_r32

I'm going to say this slowly again, one more time : All... Nissan... boxes... since... at... least... the... 60's... have... had... synchromesh... on... all... forward... gears. For good measure, the GTR also has it on reverse.

I dont know enough about other box's, only have rb25 and rb26 gear box exp,

But from my exp with older box's the synchro will start to fail will age and with a FULL gearbox rebuild will be back to new. HOWEVER, this is with older cars that are 40years old :( Not 20year old nissens.

I dont see why the synchro would fail in a 20 year old car unless its been pushed hard.

Edited by BNR32t
I'm going to say this slowly again, one more time : All... Nissan... boxes... since... at... least... the... 60's... have... had... synchromesh... on... all... forward... gears. For good measure, the GTR also has it on reverse.

ok, im not disagreing with you, and i'm not saying you are wrong. you are probably correct. all i'm trying to say is that i don't have syncro in first.

one of my close mates who has been into imports long before me, and has driven an s15 for like the last 7 years told me that allot of Nissan boxes don't have syncro in first. maybe he was wrong i am just trying to work out what box i want to go to and whether or not i will buy a 25 box or go for another 20 box. I'm not trying to say you are wrong in any way I'm just trying to get an idea of what most people think i should do? i didn't mean to offend you so if i did i apologize.

I dont know enough about other box's, only have rb25 and rb26 gear box exp,

But from my exp with older box's the synchro will start to fail will age and with a FULL gearbox rebuild will be back to new. HOWEVER, this is with older cars that are 40years old :( Not 20year old nissens.

I dont see why the synchro would fail in a 20 year old car unless its been pushed hard.

i actually believe the gear box and engine have been pushed hard, as i believe one of the previous owners in japan used to race it on the track. but have to say it is interesting that despite being pushed so hard the engine still has full compression even at 190,000ks

And if you have a look at page CH-31 of the GTR service manual, you will find a 1'st gear synchro baulk ring.

I stand corrected, still, yet to drive a GTR that 'feels' like it has a first gear syncro :)

For good measure, the GTR also has it on reverse.

You learn something new everyday :(

Edited by infamous_t

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

    • Thanks, I removed the fuse and the relay from the car and made my own circuit with them to test them with a test bulb.  I will look for the wiring diagram and go from there.
    • Jdm DC2R is also nice for a FF car compared to the regular hatches of the time.
    • Now that the break-in period for both clutch and transmission is nearly over I'd like to give some tips before I forget about everything that happened, also for anyone searching up how to do this job in the future: You will need at least 6 ton jack stands at full extension. I would go as far as to say maybe consider 12 ton jack stands because the height of the transmission + the Harbor Freight hydraulic platform-style transmission jack was enough that it was an absolute PITA getting the transmission out from under the car and back in. The top edge of the bellhousing wants to contact the subframe and oil pan and if you're doing this on the floor forget about trying to lift this transmission off the ground and onto a transmission jack from under the car. Also do not try to use a scissor jack transmission lift. You have to rotate the damn thing in-place on the transmission jack which is hard enough with an adjustable platform and a transmission cradle that will mostly keep the transmission from rolling off the jack but on a scissor lift with a tiny non-adjustable platform? Forget it. Use penetrating oil on the driveshaft bolts. I highly recommend getting a thin 6 point combination (box end + open end) wrench for both the rear driveshaft and front driveshaft and a wrench extension. These bolts are on tight with very little space to work with and those two things together made a massive difference. Even a high torque impact wrench is just the wrong tool for the job here and didn't do what I needed it to do. If your starter bolts aren't seized in place for whatever reason you can in fact snake in a 3/8 inch ratchet + 6 point standard chrome socket up in there and "just" remove the bolts for the starter. Or at least I could. It is entirely by feel, you can barely fit it in, you can barely turn the stupid ratchet, but it is possible. Pull the front pipe/downpipe before you attempt to remove the transmission. In theory you don't have to, in practice just do it.  When pulling the transmission on the way out you don't have to undo all the bolts holding the rear driveshaft to the chassis like the center support bearing and the rear tunnel reinforcement bar but putting the transmission back in I highly recommend doing this because it will let you raise the transmission without constantly dealing with the driveshaft interfering in one way or another. I undid the bottom of the engine mount but I honestly don't know that it helped anything. If you do this make sure you put a towel on the back of the valve cover to keep the engine from smashing all the pipes on the firewall. Once the transmission has been pulled back far enough to clear the dowels you need to twist it in place clockwise if you're sitting behind the transmission. This will rotate the starter down towards the ground. The starter bump seems like it might clear if you twist the transmission the other way but it definitely won't. I have scraped the shit out of my transmission tunnel trying so learn from my mistake. You will need a center punch and an appropriate size drill bit and screw to pull the rear main seal. Then use vice grips and preferably a slide hammer attachment for those vice grips to yank the seal out. Do not let the drill or screw contact any part of the crank and clean the engine carefully after removing the seal to avoid getting metal fragments into the engine. I used a Slide Hammer and Bearing Puller Set, 5 Piece from Harbor Freight to pull the old pilot bearing. The "wet paper towel" trick sucked and just got dirty clutch water everywhere. Buy the tool or borrow it from a friend and save yourself the pain. It comes right out. Mine was very worn compared to the new one and it was starting to show cracks. Soak it in engine oil for a day in case yours has lost all of the oil to the plastic bag it comes in. You may be tempted to get the Nismo aftermarket pilot bearing but local mechanics have told me that they fail prematurely and if they do fail they do far more damage than a failed OEM pilot bushing. I mentioned this before but the Super Coppermix Twin clutch friction disks are in fact directional. The subtle coning of the fingers in both cases should be facing towards the center of the hub. So the coning on the rearmost disk closest to the pressure plate should go towards the engine, and the one closest to the flywheel should be flipped the other way. Otherwise when you torque down the pressure plate it will be warped and if you attempt to drive it like this it will make a very nasty grinding noise. Also, there is in fact an orientation to the washers for the pressure plate if you don't want to damage the anodizing. Rounded side of the washer faces the pressure plate. The flat side faces the bolt head. Pulling the transmission from the transfer case you need to be extremely careful with the shift cover plate. This part is discontinued. Try your best to avoid damaging the mating surfaces or breaking the pry points. I used a dead blow rubber hammer after removing the bolts to smack it sideways to slide it off the RTV the previous mechanic applied. I recommend using gasket dressing on the OEM paper gasket to try and keep the ATF from leaking out of that surface which seems to be a perpetual problem. Undoing the shifter rod end is an absolute PITA. Get a set of roll pin punches. Those are mandatory for this. Also I strongly, strongly recommend getting a palm nailer that will fit your roll pin punch. Also, put a clean (emphasis on clean) towel wrapped around the back end of the roll pin to keep it from shooting into the transfer case so you can spend a good hour or two with a magnet on a stick getting it out. Do not damage the shifter rod end either because those are discontinued as well. Do not use aftermarket flywheel bolts. Or if you do, make sure they are exactly the same dimensions as OEM before you go to install them. I have seen people mention that they got the wrong bolts and it meant having to do the job again. High torque impact wrench makes removal easy. I used some combination of a pry bar and flathead screwdriver to keep the flywheel from turning but consider just buying a proper flywheel lock instead. Just buy the OS Giken clutch alignment tool from RHDJapan. I hated the plastic alignment tool and you will never be confident this thing will work as intended. Don't forget to install the Nismo provided clutch fork boot. Otherwise it will make unearthly noises when you press the clutch pedal as it says on the little installation sheet in Japanese. Also, on both initial disassembly and assembly you must follow torque sequence for the pressure plate bolts. For some reason the Nismo directions tell you to put in the smaller 3 bolts last. I would not do this. Fully insert and thread those bolts to the end first, then tighten the other larger pressure plate bolts according to torque sequence. Then at the end you can also torque these 3 smaller bolts. Doing it the other way can cause these bolts to bind and the whole thing won't fit as it should. Hope this helps someone out there.
×
×
  • Create New...