R34 manual gearbox swap to RB20DET (SMALL BOX)

[RB25inside]

Okay update I have placed an order on the parts. The speed sensor is coming from the USA so it will take some time for it to come over to AUS early FEB some time. But I am also getting some other parts at the same time like a rear main seal (May as well do it while I have to box out) 

I will keep the form posted how I go

[RB25inside]

Found this neat website that lists all the details about the 71-Series transmission (RB20DET) speedometer gears and ratios / history. The website also lists what is compatible with what. 

http://datsun1200.com/modules/mediawiki/index.php?title=71

 

Also web archived it for future uses (If needed  )

https://web.archive.org/web/20240109124810/http://datsun1200.com/modules/mediawiki/index.php?title=71

[GTSBoy]

There's some problems with the "technical editorial" on that page. The author goes on about how the 71C is real strong and handles 3L turbos just fine. And it's just not true. I killed the input shaft bearing on 2 of these behind an RB20DET making only ~170rwkW. They just aren't tough enough to handle that sort of torque for very long. I wouldn't even contemplate it behind a 25DET.

But otherwise, that's a good find.

[RB25inside]

Just letting you guys know that the R33 brake pedal has a higher pitch bracket on it so it didn't line up with the R34 auto 5th dash screw. 

Ended up drilling a hole in it and putting a thick spacer in between. All seams very tight.

[DatsunBanana]

Couldn't quite see what you mean from your photos, can you share a pic of the drilled hole and spacer? Still promising myself that one day I'll fit all the manual bits I've got in the garage. Is the rusty one the R33 pedal?

[RB25inside]

I certainly would but it's all in the car now 🥺 the R33 pedal is the rusty one. I was able to figure out where to drill it by putting them side by side from one another and used some rulers. As the R33 pedal was a higher pitch and longer I used a thick 2CM high pipe (was going to use a couple of nuts) to fill the gap. Made sure it was all tight and solid would hate for my brake pedal to not function 😳

Other then that I have been using the pedal for a while now and it all seems to be good have checked that it's still tight which it is

Just got the speed sensor in the post so I'm waiting for the hoist to be free anyone know what the recommend oil is for the RB20DET box?

[DatsunBanana]

Nice! That makes perfect sense now - thanks 👍

[RB25inside]

Okay I have got the speed sensor in the mail from the KA24DE (S13 MODEL) all bolts in nicely

Spoke to another guy who did the same swap in his N/A R34 and he said that the car used the speed sensor off the differential (Not sure how that works) but I will give it a shot and test it.

If all else fails and neither of those work I'll buy an S14 speed sensor and test.

Man this has been a rabbit hole 😂

Edited February 9, 2024 by RB25inside
Needed to edit the speed sensor model

[RB25inside]

*** UPDATE ***

I have done it the gearbox is in the car and it is rolling Car feels so much more responsive with the RB20DET box. Will keep you updated how it goes.

So as it turns out I didn't have to use any speed sensor. The rear drive shaft has an abs sensor which detects speed. So I didn't end up using the S13 speed sensor.

I checked that the Speedo was reading right with two different GPS apps on two different phones and it all lines up. So the R34 GT NA dont seem to need a speed sensor from the gearbox. Instead of runs off the ABS system 💪

[niZmO_Man]

That's good, because the gears for the speedo inside the gearbox can break if you don't have matching sensor (on the pre-R34 era cars), then you're screwed haha.