Rb25 S2 with rb20 transmission

[specialedition]

Hey guys,

Planing on doing an rb25 s2 swap in my r32. In a way to save money and time finding an rb25 tranny. Has anyone put the 20 tranny onto the 25?

What do you guys think worth it or not please explain.

Thanks

[Supraclean]

Buddy of mine is using his rb20 tranny with his series 2 atm, no problems and hold up fine to the abuse of the stock 25.

[Skym]

Gearboxes have a torque rating / design limit.

Like a 5 speed S13 / 240sx gearbox (similar internals, different housings and both use same part number which is FS5W71C) is said to be good to around 30kgm x 9.80665 = 294.1995nm (design limit) -

http://www.nismo.co.jp/en/products/competition/mission/silvia.html

RB20DET produces around 264nm when stock and RB25DET is around 319nm. You have to remember a stock gearbox is designed for a stock engine or lightly modified stock engine.

But in saying that, one person has put a high km RB20DET gearbox behind a 310rwkw RB20DET with I think was slick tyres and it worked (not sure for how long). So torque ratings are rough guides for longevity of gearbox, as how you drive car (reach peak torque often or not) will determine how long it last's. Even clutch you use plays a role (solid or stock spring type clutch disc).

RB25DET gearbox would require gearbox cooler, pump setup due to lack of air around gearbox to cool it in R32 gearbox tunnel (if used on racetrack, motorway, etc).

Also there are race bearings that can be used (for R34 GTR transmission, etc). Not sure if available for older transmissions.

[specialedition]

Im pretty stock engine wise. I think itll work out for the mean time! Thank you Supraclean and Skym for the replies!

[supersayianjim]

iam using one on a bolt on s2 engine. i will let you know how it holds up!!

[Skym]

If could afford it, a modified Tremec T56 gearbox (fits behind V8's, etc) with custom CNC adaptor plate for non Skyline bellhousing or custom CNC bellhousing, as they can take up to 700flb (949nm or around 3x what a stock SR20DET gearbox can handle) -

http://www.hurst-drivelines.com/?page_id=4416

From what I understand, they are popular with drifters and can find gearbox second hand, as it's used behind alot of V8's.