Rb25 Tranny Vs Rb26 Tranny

[Charles W.]

I am currently doing a RB26 swap to my R32 gtst. I have searched on this in all the silvia forums regarding on making the rb26 rwd. There are different method but i wonder which one will be better. Should use the GTR tranny and cut the transfer case? then weld a plate on top? or should i just get a RB25 tranny? i am asking because i know it will take some work to get the rb25 to work with gtst cluster. Also, the engine will come with a gtr tranny so i dont want to sell it and buy another unknown condition rb25 tranny. Is the GTR tranny going to work? whts the bad side of cutting the transfter case off?? thanks

[Risking]

Why exactly do you want to cut the transfer off when it unbolts from the rear of the transmission??

Generally the easist way is to remove the Transfer open it up and have it modifed to suit. Most places compentant with transmission work can do it. What area are you located in?? By far the neatest and probably more simple solution is to buy an RB25 box even if its stuffed. You can use the RB26 gearset minus the ouput shaft and build a good RB25 box out of it.

[Charles W.]

what i mean to cut the transfer case of its that i want to remover the part that sticks out. and bolt a plate over to cover the hole. I am located in Canada and there is no one doing a rb26 swap to a gtst that i know of. My plan was orignially save the money of getting a rb25 box n use it to rebuild the engine. i know the cutting part sounds weird but i have seen some people doing it, don't know if it is the best way though.

[sh@un]

Just buy an RB25 g/box and be done with it.

[turboedsloth]

^^^ wat he said. to much time, effort an money involved to do wat ur talking about

[9krpm]

I have similar scenario.

I have both gearboxes. Would I be able to swap the internal gears from the RB26 box to the RB25 box?

[2rismo]

No point. Buy an RB25 box and use that. They're very strong. I would say, equally strong.

[Cubes]

Charles W,

GTRBen did exactly what you are talking about and was goign to fit it in to his RB30DET S13.

I remember seeing some pics with it in the tunnel but for what ever reason he ended up not finishing the *rb26 g/box* project and bolting up an rb25t box.

I don't see Ben around here all that much any more but it wouldn't hurt to drop him a PM.

Be sure to update the thread with any issues etc and why he decided to not go with it if he responds.

[R31Nismoid]

25 & 26 box are basically identical im lead to believe.

Obviously one has a transfer case, one doesnt etc. But internally they are the same thing.

So... just use a 25 box and sell the GTR box off. You'll come out infront cost wise as opposed to having the transfer case removed etc

[Charles W.]

thanks for the reply guys and i really appreciate it. A rb25 box is very hard to come across, let alone finding a good condition one. but yea, i will drop him a pm and hopefully he can give me a hand.

[Marco-R34GTT]

Well the Rb25 box is only a 5spd isn't it?

[sinistaGTR]

yeh im 99% sure they use the same geaset yes the gtr is 6 speed but im along the same lines as r31nismoid here

[STATUS]

it depends on your usage, i have modded a few GTR transfers to RWD only see pic. i even have a spare in the shed.

The benefit of using a GTR trans is they are dirt cheap on average i would pay between 500-800 for a complete setup. The gtr box and modded transfer has much better support (4 bearings vs one) on the output shaft so takes abuse like drifting far better, in fact TRUST japan uses a GTR box and modded transfer behind their sr20 D1GP car as it lasts far longer than the GTs-t equivalent. (something to do with the way the load travels up the output shaft).

the downside is the time and effort to make it happen, i built one up for our RB26 powered s13 but found that due to some other issues i was unable to fit it in the tunnel without reworking the custom handbrake setup and so forth. I ended up using a R34 gtt box.

only the R34 is a 6 speed and it wont fit.

R33 gts t and R34 GTT are the same box but the R34 has some nice subtle upgrades ive noticed.

Edited April 20, 2007 by URAS

[R31Nismoid]

clutch arrangement is also different R33 S1 to late R33/R34

[Risking]

There is aheap of info around now about the 25/26 boxes.

They are the same gear set, identical in every single way. Like Uras has said the output shafts are a different length and supported slightly differnt but other than that they are the same same.

You can't take the GTR gear set out and drop it straight into the GTs't housing because the shaft differences for the trasnfer. You need to get a GTS-t output shaft and have the gear set fitted onto this shaft then fitted into the housing.

Ive dont plenty of them its not a hard thing to do with the right tools.

[Abo Bob]

Risking, I reckon there is money to be made there. As mentioned above, GTR boxes are dirt cheap and GTST boxes are getting hard to find I've been told. I guess this only helps where you have a dead r33 box though and doesn't address the shortage of r33 boxes.

Uras, in a bigger car with stock handbrake setup (eg R33gtst) would you think the modded GTR box will fit? Also I remember reading about your car in HPI I think where you said you thought the R34 box was stronger than the R33 one (pretty sure it was you). What makes you think that? What are the subtle differences you talk of?

I'm certainly no expert so I'm not being a smart arse with these questions. The only thing I've noticed from the outside is the R34 box is much lighter as the casing is made with much more aluminium in the alloy. The down side is that it's very soft and easy to thread the bell housing bolts.

[Risking]

Yeah I agree hence why we do the conversion. If you have a dead GTS-t box and can get a GTR box fro cheap its really very simple to re-build the GTS-t box with the GTR bits using the original output shaft.

Unfortunatly alot of people tend to do exchange R33 boxes with wreckers and they end up being lost or dismantled for parts making it very difficult to get the housings.

You may remember seeing a box in bits near your diff that I was actually building at the time to go into an R32 RB25.

I have fitted full sized GTR boxes into the R33 GTS-T before but im not sure about the 34. From memory the floor pans are very similar and Id say it would fit.

R34 boxes are very similar to the Z33 gear set all bar the extra gear and selector obviously, id be interested to hear Trents opinion on the R34 5 speed as im not a fan of the Z33 box at all

[Abo Bob]

My r34 box has a selector issue in that sometimes when rushing from 4th to 5th I put it in no mans land between 3rd and 5th gears and it crunches. I know of other R34 boxes that do this too.

[Risking]

Could be a few things. Probably fimd the previous owner of the box rested a little pressure on the gear stick in 5th and may have put some premature wear on the face of the selector fork so it wont engage, Could have a problem with the Gate on the selector.

I have this same problem with my GTR from time to time and I know its cause I rest my hand on the stick with a little presure whenever I drive it to work cause im lazy

[STATUS]

clutch arrangement is also different R33 S1 to late R33/R34

yeah i just use the earlier bellhousing on the 34 box.