RB25DE gearbox speed sensor

[Black 1via RB25det swap]

Hey Guys,

I actually have this post running on another forum already which is generating some answers but would like some second opinions.

I have a 1991 1Via with an RB25det engine swap. It's paired to an RB25de gearbox.

I'm trying to get the correct speed sensor to fit it and get my speedometer working.

I've got an RB25DET speed sensor which fits into the gearbox hole but doesn't mesh with the Speedo drive because I believe the DET sensor is longer than the DE version and has 20 teeth instead of 21.

I'm lead to believe that the RB25DE speed sensor is actually common / shared between both the RB20DE and DET gearboxes. I have an RB30DE speed sensor and I know that doesn't fit the 25DE gearbox.

What I'm after is if anyone knows the exact part numbers of the below:
RB20DET speed sensor
RB20DE speed sensor
RB25DE speed sensor

Or if anyone knows anything different to the above info with pics.

Cheers Al

[robbo_rb180]

use the rb20 speed sensor. From memory I think(going back 10 years or so) you can use the sr20 speed sensor or the gear so speedo should be right.

[GTSBoy]

RB25DE box is same box as RB20DET. So cable speedo drive or electronic senders will cross-pollinate between them. The 35DET box is a completely different box, so the speedo sender will not work with the skinny boxes.

As Robbo suggested, the 4cylinder box's speedo drive should be same enough with the Rb skinny boxes, but there's no guarantee that the output speed will be correct. It might be, but I don't know for sure.

Keep in mind that the electronic speedo sender in the box sends an AC signal to the dash. The dash converts that into a ~5V PWM square wave signal for the ECU. So all 3 parts have to be correct to get everything working perfectly. Sometimes near enough will be near enough.

[Rusty Nuts]

5 hours ago, Black 1via RB25det swap said:

What I'm after is if anyone knows the exact part numbers of the below:
RB20DET speed sensor
RB20DE speed sensor
RB25DE speed sensor

According to the R32 parts manual they all use the same speed sensor 3270258S21 the 21 on the end indicates the teeth.

[Black 1via RB25det swap]

Okay guys I have finally sourced the appropriate sensor for the RB25DE gearbox. I now have an RB25DE/RB20det, RB25det and RB30DE sensor. To save any people the future hassle of going through this please see the below photos of the sensors next to each other. I will attach photos of dimensions to so you can know what you're after. The RB25DE sensor is indeed shorter than the 25DET sensor and has 21 teeth on the purple pinion head as opposed to the 20 teeth on the 25DET red pinion head. The RB30DE speed sensor is the greeny/blue pinion head and has a OD of only 28mm as opposed to the RB25 sensors which both have an OD of 30mm to enter the gearbox.

[Noble__1]

Hey I am having a similar issue. Have a gtt Nismo cluster for my r34 GTV, everything works except for the speedo. I believe this to be a speed sensor issue and the difference in teeth on the worm gear. The r34 GTV runs the RB20DE gear box. Were you able to solve this issue with the different speed sensors?

[GTSBoy]

Shouldn't make any difference. The speedo should work. It might be wrongly calibrated, but it should work.

[niZmO_Man]

gear inside the gearbox broken? Or something wrong with your speedo?

[Noble__1]

On 10/01/2022 at 12:23 PM, GTSBoy said:

Shouldn't make any difference. The speedo should work. It might be wrongly calibrated, but it should work.

I connected it up but the speedo doesn't work. i also get the engine code 14 for speed sensor which causes the hicas to lock up and the power steering pump to not work. I have connected my old cluster in and it works fine again. apparently i need the r33 rb25de signal sensor which fits the transmission but sends a larger pulse for the speedo and ecu to read.

[GTSBoy]

On 1/14/2022 at 12:08 PM, Noble__1 said:

apparently i need the r33 rb25de signal sensor which fits the transmission but sends a larger pulse for the speedo and ecu to read.

I can't see this being likely. As far as I know, all the Nissan inductive gearbox speed sensors output about the same thing - a -1 to +1 volt AC/sawtooth wave, with the magnitude varying a bit with speed, but the main information in it being the frequency.

This goes to the dash. The ECU does not see this signal. The dash outputs a square wave PWM 0-5v speed signal.

You can see all this in the workshop manuals.

[GTSBoy]

Spin all your sensors with a battery drill and watch the signal on the output wires with an oscilloscope. You'll see what they do. If you don't have a scope, you can use a multimeter set to a low AC voltage. It won't show you the frequency, but you should see a voltage, which should all be similar.

[Noble__1]

So could it then be a faulty speedo then? if the speed signal is no different what else could need changing, I did see the r34 service manual and the AC wave the ECU receives? and why would my engine light with code 14 engage?

[Waz1]

Noble, I've had this exact issue as you the last two weeks and Ive found heaps of people with the same problem on the forums but never a solution. After heaps of trial and error, Ive worked out why some people can do cluster swaps in 34s and they will work and some can't.

 

Ill start by laying out how the speed sensor systems work in 34s. They are unlike any other skyline. It all depends whether the base shell was ABS only, or ABS and TCS equipped, whether the car is a GTT, GTV or GT base doesnt matter.

 

Starting with an ABS only car. The car has three speed signals, one in the diff nose, and two in the front, one for each front wheel. These sensors are used for the ABS system, and the speed signal. All three wheel speed signals are fed into the ABS ECU, a small black box that is under the glovebox area on the passenger side. This box modulates the signals from a raw sawtooth wave to a square wave, and then feeds that modulated square wave signal to the dash cluster for a speed reading. In this case the cluster expects  a modulated square wave signal, and cant read any other signal.

 

Moving to a TCS and ABS equipped car. In this instance there are 5 speed sensors. Four are for the TCS and ABS system: one on each front wheel and two in the diff. All four of these signals are fed into the TCS and ABS ECU which is in the boot now. These sensors are dedicated to the TCS and ABS system only. The fifth sensor is a dedicated speed sensor that is on the gearbox. This sensor sends a raw modulated sawtooth signal straight to the cluster. In this case the cluster expects a raw sawtooth signal.

 

The issue comes when you try to swap a ABS and TCS cluster to an ABS only car, or vice versa. The cluster speedo wont be able to read the signal it is receiving. My guess is the Nismo cluster you have is for a ABS and TCS equiped car, and you have an ABS only shell. To solve your issue, find a speed sensor that fits your box and run the wiring direct from the speed sensor to the cluster to bypass the ABS box. The brown wire coming out of the sensor goes to pin 19 on the back of the cluster, and the black wire goes to chassis ground. 

 

If the issue is the other way round, and the cluster is an ABS only cluster and the shell is a TCS and ABS shell, its a bit harder. You need to source a front ABS only ECU, find the wiring diagram to power it up and run the speed sensor wires to it, and run the modulated output to the dash. More of a pain than anything, I would suggest grabbing a different cluster that is compatible. Hope this helped.

[Noble__1]

@Waz1Thanks, that is very helpful my chassis is a ABS only, is there a way to tell if the cluster is a TCS and ABS cluster or does shining a torch into the back of the bulb socket good enough? The nismo cluster does however have all the sockets for it e.g. TCS off and SLIP lights.

Edited January 17, 2022 by Noble__1

[Waz1]

Shine a torch through the SLIP and TCS OFF bulb sockets in the Nismo cluster, if you can see the warning lights its a TCS and ABS cluster and because you have an ABS shell you will need to run a dedicated wire from a gearbox speed sensor to the cluster.

[R34 Sedan Fan]

On 8/1/2021 at 2:22 PM, Black 1via RB25det swap said:

Okay guys I have finally sourced the appropriate sensor for the RB25DE gearbox. I now have an RB25DE/RB20det, RB25det and RB30DE sensor. To save any people the future hassle of going through this please see the below photos of the sensors next to each other. I will attach photos of dimensions to so you can know what you're after. The RB25DE sensor is indeed shorter than the 25DET sensor and has 21 teeth on the purple pinion head as opposed to the 20 teeth on the 25DET red pinion head. The RB30DE speed sensor is the greeny/blue pinion head and has a OD of only 28mm as opposed to the RB25 sensors which both have an OD of 30mm to enter the gearbox.

Hi 

Thanks for your effort in collecting all this info. Would you know where I could purchase the purple speed sensor? I have a 1998 R34 non-turbo, auto sedan. Engine is Neo RB25DE. Thank you.