RB20 trans vrs RB25 trans

[turbot304]

So they say the 25 is much stronger than the RB20 transmission> OK i will believe that, but just how much? I got this car with the RB25 mated to the RB20 trans and it already had input shaft bearing noise when the clutch is out and its the same a year latter, not to mention its putting down about 300 to 350 RWH but now Ive made many mods over this winter (shooting for 400 to 450 RWHP) and feal I should start with a new trans , I want to do the RB20 trans over the 25 trans for the fact that I can just put it in with out (CORRECT ME IF I AM WRONG) different mounts and shorter drive line (Mckinney motorsports) .......O ya the car has the rear suspension from the skyline , so I dont know if the U joint from the rear end is the same distance from the trans vrs KA rear end.

P.S. could I just use the RB20 trans and use some nice anti wear oil additives?

O ya and I am not a fan of slamming gears and if I do get on it at the light I do it Discriminately>RPM VRS SPEED

[Scott Buwalda]

A good friend of mine, a tuner in new Zealand, has endurance track cars with RB25's and RB30's using the RB30E box, which is basically equivalent to the RB20, pushing 450-550 wheel horsepower for 8 hours at a time. Put some good oil in it, don't do 8,000 RPM clutch dumps, and you'll be good to go. Take the money you saved and do a full round of synchro's, change the 3rd gear, and still have $500 left over. The RB20 box is not as weak as internet experts would make you think.

Scott

[BoostFab]

ppl that break their rb20 transmission due to violent launch from drag. if you dont abuse your transmission like that it should hold up ok.

[pirate87]

for a good local example, JGY is using a 20 trans mated to their ~500hp RB25 Fox-Body mustang

...also is what I'm using, but I'm not making the power, nor has my car been running long enough to be a good example

[Joe]

i have a 20 trans in my car

have 2500 track miles on it, more 5000+rpm clutch kicks than i can remember and have never had a grind or a problem.

i only run redline lightweight shockproof gear oil.

[URAS]

The RB20 boxes last about 3 meetings in a drift type environment the rb25 ones will last nearly two seasons. (this is top level drift i am talking about to, not secondhand tyre beginner type drift)

The RB20 and SR20 boxes are nearly indentical inside (rb20 has longer mainshaft)and suffer badly from bearing and selector failures when driven hard.

The RB25 box is IDENTICAL to a GTR box cluster wise but the GTR has a shorter mainshaft. We have not broken one this year and our car makes 330 rear wheel kilowatts or 450 rear wheel horsepower.

The RB25 box is around 4 times stronger.

i do alot of RB25 box to SR20 engine conversions for serious track and street cars and and decent RB's will kill a 20 box in a matter weeks.
Modified by URAS at 11:18 PM 5/7/2007

[Joe]

The RB20 boxes last about 3 meetings in a drift type environment the rb25 ones will last nearly two seasons.

all depends on your power output.

[turbot304]

WOW thank you for the outstanding and what sounds like honest replies guys

[turbot304]

Wow, thank you alot there Scott, sounds like the way to go BTW I just spent some time looking for a rebuild kit for the RB20 transmission >no luck, would you be able to turn me in the right direction?

[Scott Buwalda]

Naw man, I had my box all done up by my mate in NZ.

On an unrelated note, I have fubarred my reverse (long story). So I'll be popping mine out very soon as well. I have a GTR box sitting here. Now I just need to find someone local to TIG well the diff casing shut.

Scott

[pirate87]

The RB25 box is around 4 times stronger.

Do you have a basis for that number?? Or was it just the first round digit to pop into your head?

[URAS]

Naw man, I had my box all done up by my mate in NZ.

On an unrelated note, I have fubarred my reverse (long story). So I'll be popping mine out very soon as well. I have a GTR box sitting here. Now I just need to find someone local to TIG well the diff casing shut.

Scott

i do quite a few of these for circuit series cars. The Greddy D1GP S15 runs exactly the same setup, but with a quaife gearset.



whole discussion here http://www.skylinesaustralia.c...64613

[URAS]

Do you have a basis for that number?? Or was it just the first round digit to pop into your head?

haha cause you would know?

in fact if you compare gearsets next to each other you would have a far better understanding.

i have been building "s" series race cars for close to 12 years now and specialise in gearbox conversions, engine building and race car setup. In fact 1/4 of the top level drift cars in australia have setups i have provided directly and i consult on probaly 1/3rd of all the cars in the elite series.

[pirate87]

certainly not arguing your credentials, just seems like it'd be hard to put an actual number to comparing strength/reliability

[GTR Shop]

You will break output shafts on a RB20 box with slicks and drag launches with ~450hp. Not 1st pass, but it will break.

RB25 box, 650hp same and no probs.

[Bart]

Hey guys sorry to intrude, but i need to ask what is the part number of the RB25 turbo gearbox? as im planing on buying one and want to make sure what im buyingthank you

[URAS]

Hey guys sorry to intrude, but i need to ask what is the part number of the RB25 turbo gearbox? as im planing on buying one and want to make sure what im buyingthank you

hey i see your in australia like me, go to nissan they have the numbers there. If not speak to darren at just jap or john at unique autosports.

i just paid $1500aud for my 15,000km (i pulled it from the front cut so kays are legit) r34 rb25 box. new is around 3-4k