RB20 manual box into R34 auto

[DatsunBanana]

Hi, I've been offered an RB20 manual gearbox and I realise that's the same box as the R34 non-turbos had. I have done a plus T but it's still only running modest power so I'm OK with putting the smaller box in. The one thing I'm struggling to really find is whether the R34 NA auto box has a speedo sender that will plug into the RB20 manual? Does it make a difference which Skyline the box came from - like if it was an R32? Nissan EPC doesn't even seem to list a speed sensor for the R34 non-turbo but it does for the 300zx NA auto which is the same box. I can't find any pictures showing where it is on the autobox either.

[GTSBoy]

I wouldn't do it. The RB20DET box is reasonably strong, but nowhere near strong enough to handle the torque of a 25DET.  I killed an RB20 manual box with just modest power on an RB20, around 190 rwkW.  Not thrashed, just wore out the input shaft bearing.  Too much torque, and over a not very long time.

The other thing is that the speedo senders are almost certainly different.  You may just be lucky and the NA R34 electronic sender will fit the RB20 box.  Maybe.  The boxes might be the same, but the speedo sender/cable drive part of it might be different.  I put an RB25DE manual into my R32 after I killed the original 20DET box and it accepted the R32 cable drive.  Maybe just maybe the R33&34 NA manual boxes are all cable drive (although I can't imagine why they would be).

[DatsunBanana]

Thanks for the reply. I'm not too worried about the power capability of the box at the moment. If I go ahead then I'll be building it up on a spare RB25DE NEO I've got in the garage. If all goes well I'll transplant the lot and attach all the +t mods I've done on the current engine. So worst case scenario is that it doesn't last long but having done all the hard work on pedals, clutch etc. I'll just be forced to buy an R33 box but then it's just a straight (ish) swap.

Also I'm supposing that a few have done +T on their R34 NA manuals and just kept using the W71C gearbox already in there?

What I need to do is start buying all the bits I need and just not sure if a speed sender will be one of those things. I think you're right about it's gonna be different but I'm just not clear on what's in the auto box already and whether it will slot in to replace whatever the RB20 box has. So if anyone knows that would be great.

 

[GTSBoy]

The auto one will NOT fit the manual box.  That much for certain.

[DatsunBanana]

OK. I'm hoping there's one on the box when I see it tonight. I found out that it's off an R33 so at least it will take an electronic one if not already there.