Mystery Electrical Plug above rear diff.

[mr_manny]

Found this electrical connector above my rear differential.
Any idea what it's for?

I know where my rear anti-lock brake sensor is (just ahead of my fuel filter), so it isn't that.
Any assistance would be appreciated.

1990 Bronco II 5spd, 4x4

 

[Uncle Gump]

That looks like the rear wheels speed sensor that goes to the rear diff.

The unit in front of the fuel filter is the RABS control unit.

 

[mr_manny]

Thanks Uncle Gump, will take a closer look at the rear diff.
Might be a good idea to hit it with a pressure washer

 

[Curious Hound]

That looks like the rear wheels speed sensor that goes to the rear diff.

The unit in front of the fuel filter is the RABS control unit.

I agree

 

[lil_Blue_Ford]

That looks like the rear wheels speed sensor that goes to the rear diff.

The unit in front of the fuel filter is the RABS control unit.

That indeed does appear to be the plug for the rear wheel speed sensor in the rear differential…

Except if I’m looking at that pic correctly, that rear differential appears to be missing the place for the sensor…

Which makes me wonder if that’s the original rear axle or not…

Bronco IIs were also weird. I’ve seen them wired for both regular and premium sound in the same truck, my Choptop had wiring for stuff it wasn’t equipped with… so it’s also possible that it has electrical for things it doesn’t have… more investigation may be required…

 

[mr_manny]

I found this image online:

The round connector seems the same, now I just need to find the sensor location

 

[Uncle Gump]

That indeed does appear to be the plug for the rear wheel speed sensor in the rear differential…

Except if I’m looking at that pic correctly, that rear differential appears to be missing the place for the sensor…

Which makes me wonder if that’s the original rear axle or not…

Bronco IIs were also weird. I’ve seen them wired for both regular and premium sound in the same truck, my Choptop had wiring for stuff it wasn’t equipped with… so it’s also possible that it has electrical for things it doesn’t have… more investigation may be required…

OP stated it has the RABS control on the frame... so I was guessing the diff housing had the sensor. Cause nobody is fool enough to add RABS.

So @mr_manny

If you don't have a sensor in the diff housing... as lil blue stated... the rear end has been changed to a housing without it. Not even sure what year RABS was government mandated... but it was in the earliest Ranger/Bronco II years.

If it doesn't have it... I also wouldn't worry too much. That system was a piss poor example of anti lock brakes the rarely ever worked right.

 

[lil_Blue_Ford]

OP stated it has the RABS control on the frame... so I was guessing the diff housing had the sensor. Cause nobody is fool enough to add RABS.

So @mr_manny

If you don't have a sensor in the diff housing... as lil blue stated... the rear end has been changed to a housing without it. Not even sure what year RABS was government mandated... but it was in the earliest Ranger/Bronco II years.

If it doesn't have it... I also wouldn't worry too much. That system was a piss poor example of anti lock brakes the rarely ever worked right.

Yeah, I know he stated the module was on the frame, but that pic he posted of the rear axle, the big ears that are cast on both sides of the sensor are notably absent. They should be easily visible in that photo showing the top of the diff, but there's nothing except smooth casting. I didn't really want to just jump to conclusions, but I just don't see where it should go to. A 1990 should have one. My 88, 89, and 92 all have one.

 

[mr_manny]

Starting to look like my rear diff isn't original to my bronco.
I take it 1987 and earlier 7.5 differentials didn't have a speed sensor?

I've slowly been going through my new to me bronco II.
Changed oil and trans fluid today...didn't make it to the tcase, stuck fill plug (started another thread on this issue). Also noticed my rear u joint needs to be replaced. This is when I came across the connector above the rear differential.

Thanks to TRS, I solved a mystery vacuum line...I'm sure this connector will also be solved soon.

Tomorrow's my mom's birthday, so wrenching on the bronco II will be postponed.
Thanks again for everyone's input...It is appreciated.

 

[lil_Blue_Ford]

Starting to look like my rear diff isn't original to my bronco.
I take it 1987 and earlier 7.5 differentials didn't have a speed sensor?

I've slowly been going through my new to me bronco II.
Changed oil and trans fluid today...didn't make it to the tcase, stuck fill plug (started another thread on this issue). Also noticed my rear u joint needs to be replaced. This is when I came across the connector above the rear differential.

Thanks to TRS, I solved a mystery vacuum line...I'm sure this connector will also be solved soon.

Tomorrow's my mom's birthday, so wrenching on the bronco II will be postponed.
Thanks again for everyone's input...It is appreciated.

I’m honestly not sure when the sensor first started appearing. Now that I think about it, my 7.5 that was in the Choptop until I broke it had the sensor and that axle was originally out of an 86 Bronco II that I stripped and scrapped. So sometime prior to 86 I would guess.

The shape of that differential also looks a little odd. I’d like to see some other pics and maybe a better look at that part number, or the part number itself that is visible in the pic of the diff, that may answer axle questions.

Glad to heat that you’re fixing it up and able to find what you need on here!

 

[scotts90ranger]

Yeah, the sensor first got added in '87 if memory serves, that rear axle is a '82 casting so likely not original to a '90...

Not a huge loss, RABS is ok at best, if working correctly it does do something but a lot of times it's just annoying...

 

[SenorNoob]

I'm reading this feeling confused. I've never seen that sensor on a 1st gen anything. Or the wiring for it. Always 93+.

I have seen RABS on the earlier trucks. It was a purely mechanical thing that by the time I got to it just meant the rear brakes didn't work at all.

 

[RobbieD]

I wasn't sure either when the first year for RABS was.

So I took a quick look at the sales brochures, and it shows up in the 1989 brochure as a new thing (and no mention of it prior year brochures).

I was thinking that it came out a couple of years earlier, but apparently it was the 1989 models.

 

[lil_Blue_Ford]

I wasn't sure either when the first year for RABS was.

So I took a quick look at the sales brochures, and it shows up in the 1989 brochure as a new thing (and no mention of it prior year brochures).

I was thinking that it came out a couple of years earlier, but apparently it was the 1989 models.

View attachment 120965

Has to be earlier. My 88 Bronco II has RABS and the sensor. Maybe it was just top end models (my 88 is an Eddie Bauer) that got it prior to 89 and in 89 all models got it? I dunno. I’ve scrapped an 86 and an 87 and I’m pretty sure both of those had RABS. They were both loaded XLT models.

 

[scotts90ranger]

They liked to use the Ranger as a Guinea pig so it likely started showing up in late '87's in some but wasn't marketed until '89 or something like that...