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R32 GTR box to rwd for rb20 conversion. ASAP!!!

dangerous_daveo
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dangerous_daveo Grand Master

dangerous_daveo

Posted
Posted

As per topic but expanded a bit more.

If I were to buy an RB26 GTR gearbox, with transfer case and all, how would I go about moding it to put in to a RWD RB20 application. Is it just a simple case of unbolt transfer case, and bobs your uncle (I wouldnt have thought so, but who knows).

Really Im lost with this one. Ive just done a quick search and got no where.

All I know is it can be done, and the reason is it is normally a cheaper option. If anyone has done it can you please post in here asap. I REALLY need to know.

Cubes Grand Master

Cubes

Posted
Posted

I'm really keen to hear back on this one. ;)

I know GTR-Ben has done this and fitted the g/box up to his Silvia and RB30DET.

From what I remember you basically cut off the transfer case and weld a plate over the hole. Bobs your uncle.

Does the GTR box have a longer first gear? (compared to rb20/25)

predator Grand Master

predator

Posted
Posted

I can't see how you just "chop off" the transfer case and weld it shut.. as there must be some gears that are driving the transfer case there.. ??

gtrgearbox.jpg

GTR's do a higher speed in 1st.. thats either the gearbox ratios or the diff ratios at play..

Sydneykid Grand Master

Sydneykid

Posted
Posted

I have never done it but I have seen one done, looks/sounds like simple stuff. Unbolt the transfer case and remove the chain drive from the gearbox output shaft. Cut off the ATTESSA extension and weld an aluminium plate in its place.:(

SteveL Mentor

SteveL

Posted
Posted

You would need a custom tailshaft and almost certainly the same for the cross-member. At the very least you should check the position of the GTR cross-member compared to the GTSt type as well as the position of the shifter (eg distance from the bell-housing face).

Sydneykid Grand Master

Sydneykid

Posted
Posted
You would need a custom tailshaft and almost certainly the same for the  cross-member.   At the very least you should check the position of the GTR cross-member compared to the GTSt type as well as the position of the shifter (eg distance from the bell-housing face).

I can answer a few of those;

I know the shifter is in the same place, I checked that.

The front tailshaft was the same as the "R33GTST gearbox in R32GTST" tailshaft.

(That's basically an R33GTST yoke and front shaft (shortened) with the mounting flange off an R32GTST).

The rear tailshaft was the standard R32GTST tailshaft.

I am not so sure about the cross member, I believe it was an R32 auto one. That needs to be checked, although I had heard (not seen) that it is simple to modify/move the standard R32GTST cross member.

:(

GTR-Ben Proficient

GTR-Ben

Posted
Posted

Yep I have done it alright. It was a tight fit into my S13.. and I have yet to do the cross member and tailshaft. Those are the simple parts though.

Basically you need to open it up, remove all the gears and chain etc so you are left with a straight shaft, put the speedo drive back on.

Then weld an alloy plate on the side. I just welded the complete transfer case up.. as the bearing press outwards there is no real need to get in there once it's sealed up. :(

You need to block the chain oil feed in the middle of the shaft as well as leave the oil pump there so it can supply oil to the rear bearing..

The cleanest way would be to make a new section so you can bolt it up and seal etc.. I did it the fast way as a test. If it starts to leak etc I know it fits now so I can re do it if needed.

The GTR's gearbox mount is quite different to the GTS-T etc.. but I am thinking a combination of the 2 would almost bolt up. The GTR box is also longer and I will be using a one piece tailshaft. Making tailshafts fit is as easy as cutting and welding then balancing..

My photo's are not so flash.. will get some more.

gearbox.jpg

under1.jpg

Sydneykid Grand Master

Sydneykid

Posted
Posted
what do you mean the rear tailshaft is the same???

Mine didnt have a yoke, it had a flange?

It had a two piece tailshaft, the rear piece was the standard R32GTST.

Yep, there is a flange at the end of the GTR gearbox that the tailshaft bolts to, the GTST box needs a tailshaft with a yoke as it has a splined output shaft.

:(

dangerous_daveo Grand Master

dangerous_daveo

Posted
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Posted

I spoke to my mechanic today, he wasnt keen on the idea. Mostly because he has to charge me money to do it, and he doesnt want to charge me that much :) His words were ''its not that bad yet''.

GTR-Ben Proficient

GTR-Ben

Posted
Posted
I hope your not suggesting that anyone 'do this at home'  (cut and weld).   Basically the GTR flange output needs to be mated to the 'rest' of the GTSt shaft.

:confused:

Thats what you pay a Tailshaft expert to do.. who do hundreds a day and can supply with paper work to say it's legal...

I have had dozens done like this.

Yeah I know I said simply cut and weld.. which is simple and cheap for an expert to do.

Doing that at home would be on the stupidest things I could imagine.... lol

dangerous_daveo: Your Mechanic is right.. and the difference in price between a RB25DET box and modded RB26 Box will come a whole lot closer if you have to pay for other peoples time to do it...

It cost me nothing to do.. and GTR gearboxs are so much cheaper, I know when I blow one up, I can simple unbolt my transfer case and bolt it to another GTR box and away I go ;)

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