How Strong Is The R34 Gt-t Rb25 Gearbox?

[xanavinismo]

Hi all,

Just wanted to get your opinions on how strong a standard R34 GT-T RB25 gearbox is? Like:

• How much power can they take?
• What are their weaknesses?
• How are they at the racetrack? (Circuit, not drag racing)
• Any other info etc...

Cheers guys!

Glen

[Hadouken]

They break at exactly 251kw

[GTSBoy]

Unless you have a box made on a Friday by Yasumi-san. In which case they all break at 249 kW.

[admS15]

If it was made on Monday morning, it will only take 206kw

[xanavinismo]

Wow cant handle that much... could it handle more if made on a Saturday? =P

[Hadouken]

Only Monday to Friday

[sleptema]

Ignore all these jokers.
















It's exactly 261kw.

[admS15]

Ignore all these jokers.

It's exactly 261kw.

False. Its 261.3

[tridentt150v]

Will take 800rwkw easy..........................for 20 minutes maybe 25-30 if your lucky!!!

Seriously have a look at the dyno thread. plenty on there with standard boxes making good power.

[GTSBoy]

I feel a little sorry for the OP now. So I shall do a little to put him out of his misery.

The R34 box is the same as the R33 RB25DET box (different clutch actuation notwithstanding). It is also essentially the same box as the R32 and 33 GTRs. As such, it is a big, heavy box that is very strong. The known weaknesses are not so much "weaknesses" as much as the things that people tend to break when they push them too hard. 2nd and 3rd gear mostly.

There's no power numbers that we can put on this though. They can certainly take hundred of rwkW, but the usual "how long is your piece of string?" comment applies, both to how much power and for how long at that power level.

On the racetrack, they are a big, heavy gearbox that drives alright but isn't awesome. Typical notchy Nissan, shouldn't be hurried too much if you don't want to kill the synchros.

[Kinkstaah]

Are they confirmed to be exactly the same, internally though?

As someone who is making above the general "safe" power for this gearbox and wanting to use it, the decisions as to what to actually do become a bit relevant vs going through the rigmarole of getting some other converted gearbox, i.e T56 or CD009 350/370Z box.

[GTSBoy]

Well, they may not be exactly the same, but we're only talking detail differences here. Things like different spec clips or tiny differences in synchro profile or any of a bunch of other revisions Nissan might have done that don't ultimately affect the raw strength of the box or the way they all work after 15-20 years of use and abuse. The parentage of the 25DET box goes all the way back to the mid 80s. The VL turbo box is pretty much the same box too.

[sleptema]

I was told from someone that after around 500whp you need to start being slightly more careful. I have a mate running 550awhp in his r33 gtr with no issues yet. And that thing takes some abuse - I regularly see him taking it to the drags.

[Duncan]

In almost every case, gearbox breakages come down to driving style and to a lesser extent clutch choice. The standard gearboxes are as strong as anything in most vehicles, it is also almost identical to the navara gearbox.

If in doubt stay standard until you prove you are an abuser by breaking it....

[MrStabby]

In almost every case, gearbox breakages come down to driving style and to a lesser extent clutch choice.

Yeah, Terry from Award Diff and Gearbox says solid center clutches should be avoided at all costs.

[turboedsloth]

Yeah, Terry from Award Diff and Gearbox says solid center clutches should be avoided at all costs.

Yep, have seen triple plate solid centre clutches snap input shafts

Well, they may not be exactly the same, but we're only talking detail differences here. Things like different spec clips or tiny differences in synchro profile or any of a bunch of other revisions Nissan might have done that don't ultimately affect the raw strength of the box or the way they all work after 15-20 years of use and abuse. The parentage of the 25DET box goes all the way back to the mid 80s. The VL turbo box is pretty much the same box too.

Better style sliding hub/key/spring retainer. But essentially same box