Rb25 Box Required For L28

[gerrardq]

Hi all,

 

Located in Tas, looking for a RB25 Manual box.

 

Thanks in advance,

 

Gerrard

Edited March 19, 2018 by gerrardq

[HomeBuiltByJeff]

You may get a better response with a more accurate thread title.

[d3c0y]

Any reason you need that box? Kind of a hard expensive option, when there are much easier and cheaper choices?

[gerrardq]

Any reason you need that box? Kind of a hard expensive option, when there are much easier and cheaper choices?

 

I'm open to suggestions for other options but I'm told that a RB25 will be the optimum choice.

[GregTas]

I ran an L28 with large turbo and EFI in a 240 and the box handled the power for some years. Unless there's a special need I think an original box even if you need to rebuild one would be the best option.

 

RB25 box is very big and heavy. I'm putting one in my car now, but only because I'm going RB25. It needs a custom rear mount. Quite a bit of work in that. The speedo drive will be unlikely to clear the original gearbox mounts without some work. I suspect there would also be some work to be able to bolt it up to an L28. New custom tailshaft will be needed.

 

The RB25 boxes are not that easy to get hold of because although strong, when the power is upped they do fail. The skyline boys are always looking for them. The R33 box has a known problem where they fail to select one of the gears (third I think) when given a hard time due to a very small part in the selector failing internally. 

 

The R34 box is an improved design, but harder to get hold of. It has a pull type clutch not conventional push type. This can be converted to a push type clutch by replacing the from pivot and fork.

 

Cost about $1000 to $1500 and you can't be sure whether it's in good cond or has been given a hard time. It took me some months to find one. I went R34 box.

 

So i think it would be worth weighing up each option carefully to be sure the RB25 box is the way you want to go.

 

Greg

[gerrardq]

Thanks Greg,

 

As I don't have anything but a auto box at the moment, would you be able to point me in the direction of a standard 5 spd?

[Dionysus]

RB20 box will handle the power, be much cheaper and there is a thread on here on how to convert it to use with a L series motor.

[260DET]

RB20 turbo box will handle up to 300 horses treated reasonably well eg no drags or driftin.

[gerrardq]

Thanks for the help so far, this is my first Datsun/Nissan and I am fairly clueless,

 

Would I be right to assume from the comments that the RB20 box will bolt straight onto the L28 in a 260z 2+2 with no modification?

[my_mad_z]

Hi Gerrard,

 

Not sure if you've seen this but it's definitely worth reading: http://www.viczcar.com/forum/topic/2434-tutorial-srca-gearbox-onto-l-series-engine/

 

If you look at post #8, there's a link to a write up with pics that is also quite helpful.

 

I don't think an RB20 box will bolt straight in, the bell housing mounting points are different between RB and L series, pretty sure this is mentioned in the link above.

 

I've done the conversion using a S13 gearbox and so far it's held up fine with my L28 that generally runs between 16 - 20psi of boost... no idea on actual hp as it's only been road tuned at this stage.

 

Marc.

[dat2kman]

Who told you, that an rb25 is needed?

How did they come to that conclusion?

What motor do/are you going to run?

 

The rb20 suggestion can be an issue in a 240Z, as the floorpan hole is set further back than a 260Z.

Even in a 260z, the rb20 gearstick comes out near front of hole.

It needs a L bell, modified, a offset rear mount, but, you retain your standard Z tailshaft

A better fit option would be a S13/S14 Sylvia five speed. Only minor machining mods reqired to a L bell ( if you are using a L motor ?), and you discard the original bell.

An offset gearbox mount needs fabricating, and, your tailshaft needs shortening.

[1600dave]

Stock, standard 260Z 2+2 ?

 

Go grab an L-series 5 speed from pretty much anything (240Z / 260Z / 280ZX / 240K / Bluebird / etc), bang it in using all stock parts and off you go. There's a post stuck at the top of the "Gearbox" page on here that lists all boxes that will work.

 

There is "better", then there is "better for your purpose". I  fail to see how an RB25, RB20, FJ20, S13, etc box that will require additional work for no real gain is "better " for you (assuming stock-ish car), only real advantage is that they will be newer and potentially in better condition (assuming Nissan Silvia drift brigade haven't tortured them to within an inch of their life already).

Edited March 20, 2018 by 1600dave

[gerrardq]

The L28 I have had built isn't stock and I just want a straight forward Manual conversion that compliments the engine, the 260z is currently auto  , the engine has  Stage 2 Cam, flat top hypatec pistons, moly race rings, blue print, triple Mikuni 44s etc.

 

Do all l series 71B boxes fit up to a L28 in a 260z without issue? 

[dat2kman]

All 71 B type ( except from R30 Skylines, they are the short version of a 71B) will fit into a Z

Ie Bluebird, Skyline, 240K, 280ZX, the more fun box is the 260Z five speed, as the first two gears were slightly close, in ratio, than other regular 71B units

[C.A.R.]

.

Edited April 9, 2018 by Lurch ™

[C.A.R.]

The L28 I have had built isn't stock and I just want a straight forward Manual conversion that compliments the engine, the 260z is currently auto  , the engine has  Stage 2 Cam, flat top hypatec pistons, moly race rings, blue print, triple Mikuni 44s etc.

 

Do all l series 71B boxes fit up to a L28 in a 260z without issue? 

So you need a manual conversion kit?

Call Les Collins in Vic: he will be able to supply everything you need to convert your Z (including gearbox) from Auto to Manual: 03 5623 3108

[PB260Z]

Hi

 

Another thing to consider is your diff ratio.

As your is factory auto it will most likely have the 3.545:1 ratio diff.

 

My car was originally L26 Auto with the 3.545 diff. I swapped to an L28 (EFI) with a 280ZX Manual box then changed the diff to a 3:9. Changing the diff ratio made a massive difference to how the car performed.

 

The 3.9 is pretty good compromise, reasonably responsive but still able to cruise at 110+ without reving its head off.

 

I don't think you should go to trouble of costly gearbox until you have the car on the road with the most suitable diff, for now just grab a 5 speed and see what you think.

 

This is just my opinion.

 

Cheers

 

PB