RB25DET Gearbox - RB25DE Gearbox

[50FFT]

Hey,

just had a friend ask me if there is any way to tell the difference between a turbo and non-turbo box, if anyone knows that would be good

[R31Nismoid]

no expert here... but i'd be betting there would be a size difference (turbo being bigger)

[RB30-POWER]

From what i understand the NA had the same/similar box to the RB20DET.

There is a massive size difference if you put them side by side.

Like this

[Cubes]

Huge weight difference also.

I am able to lift the RB25DE/RB20DET box without too many problems.

The RB25DET box.. be buggered.

[predator]

b-jeebus.. no wonder they're so strong ..

[50FFT]

Thanks for that, Hey RB30-POWER are they the actual boxes? How much app. should the turbo box weigh?????????????????????????????

[R31 POWER]

From memory the left box is a MX7 from a VLT but still looks the same really.

I just weighed my R33 RB25det box with yoke and clutch fork and it came to 61kg's.If I had my RB20det box here I could of weighed that also.

[Cubes]

The MX7 is essentially the same as the RB25DET g/box?

As in shifter locations & boltup of everything, spedo cable etc?

[predator]

the old mx7 boxes are mechanical speedo.. but will bolt up yeah.. old single synchros in all gears. Not really as strong as RB25det at all..

but they are out of a VL and nearly 20 years old by now..

[Bl4cK32]

mX7 has single syncros on first to third gear though i think i read somewhere unlike the rb25det box which has double on first to third.....or could someone shed some more light?

[RB30-POWER]

The box in that photo is an RB25DET box above.

This is an MX7, notice how the MX7 (VL Turbo Box) has less webbing on the bellhousing.

Also i never seen actual proof that the RB25 box is stronger.

Usually, if you fit extra syncros you have to use a narrower gear because the extra syncros take up space. So to say the RB25 box is stronger may not neccesarily be true.

I've never seen the actual gears measured and compared between the two boxes.

[SteveL]

Usually, if you fit extra syncros you have to use a narrower gear because the extra syncros take up space. So to say the RB25 box is stronger may not neccesarily be true.

Gear width (or thickness) is the same between the 2, so in that sense the strength is the same. Having double synchros does not change the the thickness of the gears, because the extra synchro is concentric (ie one inside the other). Also I'd have to double check back at work, but 99% sure double synchros are only fitted to 2nd and 3rd gears (certainly there's no doubt that's the case for R32/R33 GTR gearboxes which are essentially the same design).

[RB30-POWER]

Gear width (or thickness) is the same between the 2, so in that sense the strength is the same.   Having double synchros does not change the the thickness of the gears, because the extra synchro is concentric (ie one inside the other).   Also I'd have to double check back at work, but 99% sure double synchros are only fitted to 2nd and 3rd gears (certainly there's no doubt that's the case for R32/R33 GTR gearboxes which are essentially the same design).

Ahh i see then.

From what i understood, if you add extra syncros you had to reduce the gearwidth, if you were using the same size housing so to speak.

I was told that dog boxes get extra strength due to making the gears wider/bigger using up the space where the syncros would normally go.

Buy maybe that wasn't entirely correct.

[R31 POWER]

Here's a pic of my R32 RB20det series1 box and a R33 RB25det series1 box.Also the Rb20 box weighs in at 40kg's

[Roy]

Bugger, so the thing weighs an extra 20kg:( Ill drefintely wait and see how long the RB20 box lasts then.

[R31Nismoid]

Yeah, the 25 box i got the other week weight heaps compared to a 20box.

MX-7's from what i've seen dont last long. Many have broken them and the one i had in my VL was dreadful to shift.

I guess they are very old now and most have seen better days

[Roy]

Whats the go with buying 2nd hand RB25 boxes. Its pretty safe buying, dump the fluid out of them and check for swarf (Synchros:() on the magnet? Or are they generally in good condition?

Im expecting it to die at Phillip Island in a few weeks, i shift like an idiot on the track and from ppl experiences the power im making will mean DOA RB20 box, especially since at the minute there is a fair bit of slop and wallow in the drivetrain:(

[Bl4cK32]

You can get caught out Troy. I got mine with noisy bearings...luck of the draw if you buy one through a private sale, especially when its out of the car. Ideally would be to go for a spin in the car its being taken out of first , but id say that would be a rare case.

I believe some wreckers offer a warranty if a gearbox is faulty when you buy one from them?...