1992 f350 speedo and rear abs problems - Ford Truck Enthusiasts Forums

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1992 f350 speedo and rear abs problems

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  #1  
Old 08-03-2012, 09:05 PM
markbrockey
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1992 f350 speedo and rear abs problems

lets start with a little story. Bought my 1992 f350 dually from my dad that we built , painted, and customized together. It did a little light towing a few times a year but was parked most of the time. it still has less than 100k. Very well taken care of and maintained. I.ve had it now since February last year and started having miner problems a few months later. started with just rear abs light coming and staying on when running. No big deal right, brakes are fine. Pulled my 25' RV a couple times after that just fine. Parked for light Cal. winter. Just started and driven a few times just to keep things moving but then noticed speddo jumping and cruise kicking off.

This year, just a couple of weeks ago I started out of the driveway and I noticed that it shifted from 1st to 2nd at a much higher rpm and hit hard going to second. (still having speedo jumping problem), I believe its hitting hard because of the increased rpm. I didn't go far and the next couple times it did the same. Then 3 days ago I went to leave and just got down the road around a couple of corners and when it shift to 3rd-OD at about 40 mph it high reeve like it kicked to neutral. I then down shifted to second quickly and it caught a gear. I turned around to go home and same thing (high reeve thing). Dropped off the wife and went to try it again. Same thing happened and saw that the speedo also quit working. Turned around to go back home and things seem to shift fine but still no speedo. Have gone up and down the road again and it shifts fine but still no speedo, and rear abs light still on.

OK, told you that to tell you this. I've been online to try to track the problem and so far not much luck. I consider myself and OK mechanic but all this newer electronic stuff, ?. So far I have pulled the VSS on the rear end but believe its good. (did the volt test with leads to volt meater and swiping a piece of metal over magnetic pick up and got volt increase). So after more internet I think rear abs light is probably abs valve on frame ? Now I have no idea were to go with the speedo problem. I know that speedo has to do with shift points but like I said earlier, now it seams to shift fine. Are the ABS and speedo problems connected or what should I look at next. Don't have mechanic money. What sucks is dad is coming to visit soon. He told me at time of sale, I don't like selling to family and like any body else I don't want to hear I TOLD YOU SO.

Well I hope you enjoyed the drawn out story but I'm hoping you have a enough details to help me or the Patience help me figure it out.
 
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Old 08-03-2012, 10:57 PM
Snowbirds11b
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Ok Your problem come realy from the speed sensor, the rab module must read
around 1400 ohms from the speed sensor or abs module bring the light on
and cancel the abs. the speedometer and the powertrain control module read the
same speed sensor ,the split wires are near the rab module and the rab module
is under the glove compartment, its a must for the PCM to control the shift point.
So check the sensor resistance , remove and check the ring gear inside the
differentiel ,if ok check for rust between the sensor and the case ,sometime
rust can backup the sensor and the gap is wrong, check the wiring and connector
for corrosion near the differentiel its the worse place. good lock
 
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Old 08-03-2012, 11:10 PM
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can you please speak USA, looking for some body that can really walk me through it. What (sensor should read what ohms, where are they located).
Come on
 
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Old 08-03-2012, 11:33 PM
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Sorry, I spend from 1985 to 2006 working as a certified technicien for FORD, I only speak the language I learn from FORD , if you dont no what '' OHMS '' mean we have a problem : the resistance of the VSS on your rear end must be around 1400 OHMS
 
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Old 08-03-2012, 11:35 PM
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And you have to read it from the abs module , that check the wiring at the same time.
 
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Old 08-04-2012, 12:08 AM
markbrockey
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I'm using a craftsman 82022 muilti meter, giving me 35.46 milamps but no reading on amp, but the other test (volts at metal passing magnetic pick up does increase volts AC, DC,And amps). Now play nice. Not every body has your ford background. I just need to know how many sensors, how many modules, and where are they at, and if possible, how to check. It took awile to type the problem and hopefully someone will spend some time to help me or at least put me in the right direction.
 
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Old 08-04-2012, 07:38 AM
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Look at the wiring to the VSS, it is vulnerable where it moves around with rear suspension movement. The sensor producing ac voltage when passing by metal isnt a foolproof test... if you want to just try something the vss is your most likely candidate.
 
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Old 08-04-2012, 09:55 AM
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I see you have a 1992.
In 1992 the VSS was called a DSS on all the wiring diagrams from Ford.
To test the DSS you need to put the rear end up on jack stands.
There is a plug under your hood at the drivers corner.
You need the meter on the AC scale.
The run the truck up to about 30mph.
The voltage from the DSS generator should increase smoothly and continuously from 0 to approximately 3.5 volts AC as vehicle speed increases from 0 to 30 MPH.
The DSS generator very seldom goes bad but as said above it could have junk stuck to it or bad wiring at the top of the rear end.

The DSS wiring:


Use the RABS plug under the hood for the DSS test:


The DSS:


/
 
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Old 08-04-2012, 10:38 AM
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I had your same problem in my 95. My problem was metal shaving clogging and packed around the sensor. Bearings went out in rear end.
Check your oil for excessive metal in. Drain, clean housing out and refill with fresh fluid. Might need a rear end rebuild.
I rebuilt my rear end. Reused the old sensor and never had problem since. Not saying that what wrong with yours but that's what fixed mine.
 
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Old 08-04-2012, 11:56 AM
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any other ideas

I have already cleaned it but was totally clean when I took it out, I've also checked rear end for shavings, totally clean. any ideas what to look at now.
Does it have a second speed sensor at the trany.(output speed sensor) if so about were would it be ?
 
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Old 08-04-2012, 12:08 PM
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The E4OD did not have the Output Speed Sensor (OSS), only the 4R70W had the OSS and they were not used in the 1992 F-series truck.

No there is not a second speed sensor at the transmission.
 
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Old 08-04-2012, 01:32 PM
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If you have tried what the others suggested and still not better. I would say go buy a new speed sensor. Just make sure the tone that the sensor reads isn't missing any teeth.
 
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