rb25 garbox on rb20

[blackrb20silvia]

hey guys just a quick question

can a rb25 garbox be bolted to a rb20

does anything ahve to be moddified or is it a direct replacemant????

cheers

mines screwed was going to get rebuilt but have heard rb25 boxes are tougher is this true?

matt

[raz0r$harP.UK]

i have one on mine... you need an r33 tailshaft as well to fit...

also a different crossmember... i have heard that one from the silvias fit but not too sure

you might have to do a search

[dangerous_daveo]

Just a realllly quick one. Does the little gear stick, stick out from the same place??? Or is some interior hacking needed?

[blackrb20silvia]

well im talkin bout putting the rb25 box in a silvia that allready has a rb20

so i hope it lines up

as for tail shaft have heard rumours that the CA shaft and box where diff the SR oh well ill have to speak to a jap wrecker or something??!!

[Cubes]

A bloke over at SDU did it and said the R32 Auto x-member bolts up to the rb25 box fine.

[inissane]

anyone know if the box is much heavier than the rb20? ratios be fine? am looking at the same thing when/if my one dies too

[sproosy]

Pretty much the same wheight dude, mabye a few kgs heavier. As far as strength is concern an RB25 box is the same as a GTR box but does have a transfer case for 4WD, so she should withstand some punishment. How much power you making?

[inissane]

who me not as much power as matt......got bits to go on for bout 185rwkw which should be fine, but it just feels a lil old (gbox) and power will only be going up, plus engine is heavy for chassis so keep an eye on weight

cheers for info

[sproosy]

no worries champ! I think if i ever wrote my32 off id get the motor out and drop it in a 180 or an S13 for sure! Have you ran it down the 1/4 mile yet?

[inissane]

nah would love to have a shot after bits n pieces on but its not gonna set the world on fire me dont suppose, good fun round corners too though and love da rb note!!

[sproosy]

Hell yeah! Nice work man!

[R31 POWER]

Just over 20kgs heavier,I weighed them.I dunno about the ratios but I'm positive the 25det box's shifter sits about an inch rearward.

[jnr32r]

Just over 20kgs heavier,I weighed them.I dunno about the ratios but I'm positive the 25det box's shifter sits about an inch rearward.

if this is so... how have pple fixd the problem ?

[PHaT MR30]

i don't know that they do or not, my mounts are about 2 inch's rearwards of the normal CA box mounts, but my engine sorta sits a bit lower and further back also.

I got RB20 box (was told it was 25, till i took it out) babow!

I can't see why they shouldn't fit, as VL's run basically an RB20 box, and VLT's run same as RB25 i was under the impression??

[Roy]

Have you looked into getting it rebuilt? If so can you give an idea of price and parts repalced?

Mine is holding in there ok after two nights of drag racing, a drift day and 8 or so track days with +215rwkws. Its still going well with good oil, so im thinking its up to the power ive got, but it is a 180,000km gearbox that did about 3,000kms of track work with the std turbo.

So basically dont want to go to the expense and added weight of an RB25 box if there is a viable alternative...but suspect ill end up with an RB25 box.

[Cubes]

Roy,

Your running that Castrol 75/90 in your box?

I've used the above.

I figured the slightly thicker warm oil will help my poor little rb20 box behind the rb30.

For the first few hundred km's the box was actually perfectly silent again. Its gone back to its usual loud input shaft bearing noise.

[Roy]

Yeh Castrol Syntrax 75W/90

http://www.castrol.com/liveassets/b...90_B1278983.pdf

The box is the same old same old when cold...it never has been brilliant. But once i have done a few kms it shifts fine, and it does feel better then the Fuchs that was in there.

Funny thing is when at the track, and when it must be pretty hot, it shifts like a new box, and for the rest of the afternoon/home etc it shifts brilliantly. After it has sat overnight and its 100% cold again it reverts back to same old same old:(

So it would seem to be a bloody good oil, but perhaps suggests it never really get sup to the optimum temperature/viscosity putting around on the street...well for my g'box anyway

[Cubes]

When cold I honestly found mine shifts a little better with the VMX 80 I had in there, it also had a tube of that Nulon G70 stuff so its not really a good comparison.

I have found that after a few changes it shifts like new again, no notchyness.

Lightened flywheels makes a noticable difference to high rpm shifts. I will definately be going back, BUT this time, one with a replaceable insert. The ceramic will rip a molly item to pieces.

[PHaT MR30]

Roy,

Here is a link that works,

http://www.castrol.com/liveassets/bp_inter...90_B1278983.pdf

I might try that oil in my box when i put it back in, had a tendancy to crunch into 4th (woulda thought 2nd or 3rd be first to get noisy).

On the topic what oil do you run in yer diff?

[blackrb20silvia]

i guess my only prob with my box is it just doesnt like second

round rev limit and bot 500rpm before

that is all its just annoying trying to hold a slide then pop second and it s just like

"he ha hmmmm get in there you son of a bi........."

i lose all power cuz i have to come off throttle

same in a straight line im sick of making a come back in third cuz i cant grab second fast enough

it makes the car seem slow its like ppl are laughing at me (V8 tosses where i live)

till ill blow past breaking traction in third (eat that bogans)

but yeah i just wanted to know if they can replace rb20 boxes

if its cheaper to get rebuilt then i will but it dont matter to much because i have to take all engine and gearbox out as one anyway (damn silvia tunnel to small)

and innisane

dont worry to much bout weight

my car with 3/4 tank fuel spare tyre all interior only weighed 1220kg on the weigh bridge

a standard 180 with all HICAS and all options weighs nearly 1240kg

so 20kg in a box wont matter to much

cheers

matt