Rb20 Box Or Sr20 Box What One Is Stronger

[Bsa]

Hey everyone iv tried searching google and all that but I keep getting mixed answers. Now I'm putting a sr in my BMW and I have a sr box and a rb20 box either one will work I just want to know what one is better I don't want stupid answers only people that have used both. The sr box is out of a 180 type x and the 20 box is out of my old 32. The sr will be running a td06h-20g so I'm hoping around 260kw which the 20 box handled before. Anyone thats thinking buy a rb25 box I know they are better but a pain to fit up to a sr. Any info would be gold

[GTSBoy]

Are you talking about putting the bellhousing half of the SR box onto the RB20 back half in order to attach it to the SR? Why go to that effort? The ratios in the SR box suit the SR20 better anyway.

[Roy]

RB20 and RB25 gearboxes bolt to the backs of RBs. So I would expect you would have the same issues using an RB20 box on an SR as you would an RB25 box on an SR.

The SR20 and RB20 internals are very similar though, with the same PPG and OS Giken part numbers anyway. So general health and age would be the determining factor one would think.

I would be sticking with the SR20 gearbox behind an SR20. Just be sensible with the sprung centre clutch and use good quality Castrol fluid and would be ok provided the car isnt being clutch kicked like a wet, stray dog

[Bsa]

Yeah that's what I would do. I just don't want to put a weaker box on when I have both available I already need a custom shaft so I don't care about that. Also the shifter is in different locations the 20 box seems to line up near perfect. I'm not to worried about gearing as the diff in using (m3 LSD) is already in the 3.8 regon I think so that would decide most of how the car reacts.

[Bsa]

Go put a rb25 box on I would need to cut and shut the bell housings bit of a mission

[Bsa]

Also what clutch should I use if I went the 20 box

[dori34]

if ur box does end up blowing, prob best to go VG30 box with the adapter plates, same stregnth as rb25 but alot of chaeper

[GTSBoy]

Bsa......Im still confused. What makes you think you can just bang an RB20 box on the back of an SR20? The RB20 and RB25 boxes have the same bellhousing as each other - not the same as the SR20.

[Bsa]

I have a sr bell housing that I will change over onto the rb20 box so it will then fit the sr20

[GTSBoy]

OK, fair enough, so my first post applies.

[Bsa]

Yeah sorry for the confusion iv never felt a sr box before well actually driven one I know my 20 box is still tight no crunching I also have a short shifter for it

[Birds]

They are for most part the same box, no real difference, just made for a different car. So go with the SR20 for ease of use. As for RB25 gearbox, you can buy SR20 adaptor plates so no cut and shut necessary. Running 260rwkw that's the path I'd heel heading down, personally.

[blind_elk]

I don't think it really matters which box you use. My experience has been that Nissan makes near indestructible gearboxes. (Although I have heard of 1 person who managed to lunch 3 RB boxes in a matter of months - probably using a VHD multi-plate clutch, and sidestepping the clutch at 7000 rpm.)

Since you are using a SR engine, it makes good sense to use a SR gearbox, IMHO.

[Bsa]

Iv just heard so many stories of people munching sr boxes that's all

[GTSBoy]

RB20 boxes are no stronger. But most RB20 cars don't get driven by the same grade of twat that drive S13s.

[Bsa]

I'm fairly careful with my things as I don't have money to throw at my car. I think I'll use my 20 box because I know it's good and cheap to replace thanks for the help boys

[Sir Lord Van Von Vader'ham]

another thing i've been told is that the SR has longer raitos. may want to scope that out for yourself though.

RB tops at around 200, SR at 240ish. (Same diff ) but again, double check that...

[Bsa]

I can tell you now my 20 box seen more the 200 got 215 (nismo 260 cluster) before I slowed down on a private road of course diff is the main controll of top speed so the m3 diff would benefit from a shorter ratio box

[GTSBoy]

Yuh, not even close to correct.  The RB20 will see over 180 km/h in 4th easily, run to much much more than 200 in 5th.  The main differences in ratios between SR cars and RB cars is that the RB diffs are shorter than 4:1 and the SR diffs are taller than 3.7:1.  The SR gearbox ratios are therefore better suited to the longer diff gears.

Bsa.  Just use the SR gearbox.  It is better suited to your engine and your diff ratio.

Edited February 3, 2012 by GTSBoy

[Bsa]

Rito sounds good what clutch you think will best suite