[Ernie295]

Bought a beautiful cherry truck. It spent most of it's life in New Mexico and everything body wise is like new .
Working out some minor mechanical issues . Seller told us that he thought the ABS sensors were bad before test drive . They were. Could feel it in pedal and through the truck . Took it to my mechanic . No codes no dash warning lights . We replaced front sensors and problem has improved . Not in pedal now but ABS applies when coming to a full stop at low speed. Pulled fuse today and problem stopped . Definitely in the ABS .
Question is this . Can the rear sensor in differential be bad ? Can't find much information online on rear sensor.

 

[j cat]

you do not replace sensors . hub sensors...
the hubs rust then the sensor is pushed out very slightly this then causes the sensor volltage at slow speed @5MPH to trick out the PCM then the ABS is activated and the brake pedal pulsations..

so to fix this step one remove tire then rotate hub by hand and measure the sensor volts must be .35volts AC or more.. so if it is less than this remove rotor and remove sensor check for any rusted grease if so hub is bad... sensor is magnet so rust will make it not work... so grease looks good then you get a file and file down the rust at the sensor hub hole so it is looking like steel not rust .. use magnet to remove the filings install the sensor the do volt test .. should be .5volts ac or more that is good.. now repeat on the other side ...

use a sealer rust paint over the sensor hub area so the rust hopefully not return

 

[Ernie295]

Its funny you mentioned cleaning the hub where the sensor fits . I have been wondering if the mechanic did this when he put the new sensor in . I will look at it tomorrow .
What about the rear sensor in the differential . From what I am reading this can effect ABS also.

I work with 2 different garages and do some work myself when time allows . Both are great to work with but it is frustrating because getting them to be proactive is almost impossible . I am crazy about preventive maintenance and fix it right the first time . these things seem to be from the past and are no longer a standard.
Fortunately the one garage services all of our company trucks and is right next door to my work so Ill get a look at it on the lift tomorrow

 

[RayVoy]

The rear sensor is in the transmission tail piece (2WD), in the transfer case (same place) on a 4WD.

 

[j cat]

Its funny you mentioned cleaning the hub where the sensor fits . I have been wondering if the mechanic did this when he put the new sensor in . I will look at it tomorrow .
What about the rear sensor in the differential . From what I am reading this can effect ABS also.

I work with 2 different garages and do some work myself when time allows . Both are great to work with but it is frustrating because getting them to be proactive is almost impossible . I am crazy about preventive maintenance and fix it right the first time . these things seem to be from the past and are no longer a standard.
Fortunately the one garage services all of our company trucks and is right next door to my work so Ill get a look at it on the lift tomorrow

the front hub sensors and rear sensor all do effect the ABS BUT REAR does effect"" speedometer"".. so this rear sensor does not effect braking when at 5MPH and less.. codes on front or rear sensor that code will throw if you have bad wiring . will not throw code if your speed is slow and the sensor volts are low.

any tech that does this work if the person is smart will measure the voltage as the hub is rotated..if not person is not qualified to do this type work.

when you buy a new hub ............these come with sensors and these are calibrated to output the proper volts AC... so installing a sensor in a old hub and no volt measuring is like throwing $$$ in a slot machine..
sensors are expensive.. I would install old sensors if the volts are low and with the hole surface cleaned see if its at the proper amount. .5AC volts is the good mid point .. less than .35 volts AC not good .25v or less does this all day long ...

 

[j cat]

This is my experience on these hubs.... other members have also done this ..when I do a brake job on the front I will remove the rotors and then the hub sensor ... sure more work ... then I get the grease gun out and pump the hub with grease ..

having doing this I have had no hub failures .. then put sensor in hole spin hub measure volts all good then put sealer over the sensor / hub to prevent rusting issues.