Crazy speedometer help...
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Crazy speedometer help...
I recently added a new vehicle to my collection, 1994 f150 5.0, E40D 4x4 ect..
Bought it knowing it needed front end work (snapped outer axle shaft on the right side)
Drove it 35 miles home, abs light came on when I came into town.
Brakes felt spongy found brake fluid leak passenger passenger side caliper no big deal!
Reading on this indacates VSS
Noticed the spedometer needle flew like crazy when I went above 50mph. Cruise couldn't seem to hold steady speed. Didn't think much of it.
After reading a bit more I am very worried I've read any thing from VSS to PSOM and so on.
I need help on which order would you start to diagnose parts in, rearend seems tight no wierd noises, clunks ect...
Truck has 150k miles 8.8 rear 3.31 gears believe it to be open diff.
Got tomorrow off with no plans so any advice on where to start would be sweet.
Also I can hardly tell the truck shifts, the only shift I can tell is overdive at 45mph and when it shifts down from overdrive I can feel it.
Bought it knowing it needed front end work (snapped outer axle shaft on the right side)
Drove it 35 miles home, abs light came on when I came into town.
Brakes felt spongy found brake fluid leak passenger passenger side caliper no big deal!
Reading on this indacates VSS
Noticed the spedometer needle flew like crazy when I went above 50mph. Cruise couldn't seem to hold steady speed. Didn't think much of it.
After reading a bit more I am very worried I've read any thing from VSS to PSOM and so on.
I need help on which order would you start to diagnose parts in, rearend seems tight no wierd noises, clunks ect...
Truck has 150k miles 8.8 rear 3.31 gears believe it to be open diff.
Got tomorrow off with no plans so any advice on where to start would be sweet.
Also I can hardly tell the truck shifts, the only shift I can tell is overdive at 45mph and when it shifts down from overdrive I can feel it.
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From: Easton,Ks
It sounds like rear end bearings to me.
Could also be wiring if the truck has a lot of vibration at higher speeds.
But you need to check the voltage at the RABS plug test point under the hood with it up on jack stands, have the truck aimed in a safe direction and well blocked then run the speed up until it does its thing.
A scope would be better but I am sure you do not have one of those to check the RABS plug test point with.
The voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle speed increases from 0 to 30 mph.
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Could also be wiring if the truck has a lot of vibration at higher speeds.
But you need to check the voltage at the RABS plug test point under the hood with it up on jack stands, have the truck aimed in a safe direction and well blocked then run the speed up until it does its thing.
A scope would be better but I am sure you do not have one of those to check the RABS plug test point with.
The voltage increase smoothly and continuously from 0 to approximately 3.5 volts as vehicle speed increases from 0 to 30 mph.
/
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So I went and drove the truck this morning just to make sure I didn't miss any clunking in the rear end I heard nothing.
Jacked it up unhooked the speed sensor and noticed the wires going into the VSS or ABS switch whatever it is called have been played with before.
Just to add this truck speedo works fine untill 25 then it will start floating back and forth more and more as the speed goes up and when your doing 65 it goes 0-65 rather quickly.
PICS!!!
https://i.imgur.com/XvjE0h7.jpg
So the picture is a little blurry, but you can see the one wire is exposed (took me 15 minutes to get the electrical tape off it)
The wires were both taped together and then taped the e-brake cable. now the one that is exposed I noticed when I was look at it, it was kinked when taped and there was a small section exposed to the e-brake cable line, would this be enough to cause my issues or am I still just hoping for a easy fix?
*EDIT*
When I drove it I would also like to add the abs light did not come on when I drove earlier, just crazy speedo.
Jacked it up unhooked the speed sensor and noticed the wires going into the VSS or ABS switch whatever it is called have been played with before.
Just to add this truck speedo works fine untill 25 then it will start floating back and forth more and more as the speed goes up and when your doing 65 it goes 0-65 rather quickly.
PICS!!!
https://i.imgur.com/XvjE0h7.jpg
So the picture is a little blurry, but you can see the one wire is exposed (took me 15 minutes to get the electrical tape off it)
The wires were both taped together and then taped the e-brake cable. now the one that is exposed I noticed when I was look at it, it was kinked when taped and there was a small section exposed to the e-brake cable line, would this be enough to cause my issues or am I still just hoping for a easy fix?
*EDIT*
When I drove it I would also like to add the abs light did not come on when I drove earlier, just crazy speedo.
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Well, just drove it after repairing the repaired wire, no real change.
Just so I am clear when testing the rabs I just use my DMM poke the two prongs and and make sure there is a steady voltage increase from 0 - 3.5 from 0-30mph?
Also forgot to say this in the first post, when I brought it home the other day as I was entering town the abs light did come on and stay on. But hasn't come on since then.
Fleet Owner
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From: Easton,Ks
I think an analog meter works better as it takes time for a DMM to work as they are an averaging meter.
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Also to this time to listen to the rearend and I still could not hear any funny noises its dead quiet aside from the tires spinning.
Should I redo this test with a analog meter?
Also I tested the dmm on a few outlets known to work and was reading correct 120 throughout my garage.
Also if it was the carrier bearings, I should be able to get away with just replacing those and I wouldn't have to redo backlash preload all the fun stuff correct? I've rebuilt the 9 inch on my 78 and put a full spool in. I don't want to do it, but if I have to I will.
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Ok so my friends analog meter is broken, won't be able to get a new one till wen. Also both were set on AC.
I did however test it with another DMM and had the same results, or is the DMM test just not accurate enough
Also voltages maxed out at 1.04 on both meters 30mph.
I did however test it with another DMM and had the same results, or is the DMM test just not accurate enough
Also voltages maxed out at 1.04 on both meters 30mph.
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From: Easton,Ks
Try unplugging the RABS module and see what that does.
It sounds like the air gap for the VSS to the tone ring may be to wide in the rear end.
MEASURE RABS SENSOR AIR GAP
Remove Rear Axle Differential Cover.
Measure the shortest distance from the RABS/VSS sensor pole piece to the teeth on the reservoir bracket (2C250) (Sensor Pole to Top of Sensor Ring).
Rotate the axle 60°-90°.
Repeat the second and third steps for a total of five measurements.
All measurements need to be between 0.127mm (0.005 inch) and 1.14mm (0.045 inch) and within 0.254mm (0.010 inch) of each other.
It sounds like the air gap for the VSS to the tone ring may be to wide in the rear end.
MEASURE RABS SENSOR AIR GAP
Remove Rear Axle Differential Cover.
Measure the shortest distance from the RABS/VSS sensor pole piece to the teeth on the reservoir bracket (2C250) (Sensor Pole to Top of Sensor Ring).
Rotate the axle 60°-90°.
Repeat the second and third steps for a total of five measurements.
All measurements need to be between 0.127mm (0.005 inch) and 1.14mm (0.045 inch) and within 0.254mm (0.010 inch) of each other.
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Try unplugging the RABS module and see what that does.
It sounds like the air gap for the VSS to the tone ring may be to wide in the rear end.
MEASURE RABS SENSOR AIR GAP
Remove Rear Axle Differential Cover.
Measure the shortest distance from the RABS/VSS sensor pole piece to the teeth on the reservoir bracket (2C250) (Sensor Pole to Top of Sensor Ring).
Rotate the axle 60°-90°.
Repeat the second and third steps for a total of five measurements.
All measurements need to be between 0.127mm (0.005 inch) and 1.14mm (0.045 inch) and within 0.254mm (0.010 inch) of each other.
It sounds like the air gap for the VSS to the tone ring may be to wide in the rear end.
MEASURE RABS SENSOR AIR GAP
Remove Rear Axle Differential Cover.
Measure the shortest distance from the RABS/VSS sensor pole piece to the teeth on the reservoir bracket (2C250) (Sensor Pole to Top of Sensor Ring).
Rotate the axle 60°-90°.
Repeat the second and third steps for a total of five measurements.
All measurements need to be between 0.127mm (0.005 inch) and 1.14mm (0.045 inch) and within 0.254mm (0.010 inch) of each other.
Thanks for your help, I should be able to pull the diff cover Wednesday.
I will see if I can get to unplugging the rabs tomorrow, but I had a few other questions.
When I was messing with the wire to the ABS sensor in the diff, I noticed that there was some play in the sensor. Only reason I bring this up is I was reading when replacing the sensor sometimes when there is rust involved it can create enough of a gap to cause problems?
I figure if there is play there's a problem and would it be a bad idea take my grinder with a wire wheel to the mounting area while in the axle along with triple checking making sure there is no play or runnout on the carrier?
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From: Ft. Lauderdale,Fl.
Also remove rear axle speed sensor & inspect for metal debris, carefully rotate rear axle by hand ( with someone's help ) slowly and feel with your finger if their are any missing or damaged teeth on exciter ring. This test can be done prior to removing axle cover.
Fleet Owner
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From: Easton,Ks
If you have play (movement) of the RABS sensor (VSS) then you should replace the sensor or at least the "O" ring that the sensor mounts in. Also while it is out make sure there is nothing stuck to it and wipe it clean.
If unplugging the RABS module does not help I would unplug the PSOM and take another voltage measurement before opening up the rear end. But work with the sensor and the twisted wires from the sensor first.
If unplugging the RABS module does not help I would unplug the PSOM and take another voltage measurement before opening up the rear end. But work with the sensor and the twisted wires from the sensor first.
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Alright sir, unplug the rabs and noticed a change.
Also one of the mounting screws was broken, so the module was sitting there bouncing around.
First thing I noticed was a little movement at 35mph. Not ANYTHING like it was before. The spedo only moved 3-4mph at 45mph. It did not move nearly as much as it did before. Did not test at 65 where it did the most but I did notice a change. Never had a car with working abs, but I also noticed the brake pedal felt better to me anyway.
I think that I am still going to have to pull the rear differential cover off to verify there is no mechanical problems and fix the play in the speed sensor before proceeding.
Would also like to note that when I hit a bump the speedo seemed to be more likely to move more like 4-5mph as compared to the 2-3 when driving on a smooth road.
Thanks for your help guys, will have to get back out there tomorrow and take a closer look at the speed sensor.
Also one of the mounting screws was broken, so the module was sitting there bouncing around.
First thing I noticed was a little movement at 35mph. Not ANYTHING like it was before. The spedo only moved 3-4mph at 45mph. It did not move nearly as much as it did before. Did not test at 65 where it did the most but I did notice a change. Never had a car with working abs, but I also noticed the brake pedal felt better to me anyway.
I think that I am still going to have to pull the rear differential cover off to verify there is no mechanical problems and fix the play in the speed sensor before proceeding.
Would also like to note that when I hit a bump the speedo seemed to be more likely to move more like 4-5mph as compared to the 2-3 when driving on a smooth road.
Thanks for your help guys, will have to get back out there tomorrow and take a closer look at the speed sensor.
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Got called into work early today, didn't have time to get out to the garage till now. Wasn't as much play in the sensor as I remember still I removed it to clean it and there was a few metal shavings on it.
https://i.imgur.com/LOjnyHf.jpg
I cleaned it no real change, so I guess I got a problem in the rear-end. Going to pull the cover tomorrow morning and see what I find.
Now while I am in there, clean all the crud off the tone gear check for:
play in the carrier
missing/chipped teeth on tone gear
crud built up on tone gear
Anything else I should be looking for?
Also just to clarify the speedo is rock solid up untill 35mph, after that it starts moving 4-5 mph and sometimes it will hold steady speed and then continue moving 4-5mph I've tested it up to 55mph.
Should have put this in the first post, but there is also electrical tape over the shift leaver where the overdrive light would be, going to peel that off and see if the light is blinking.
https://i.imgur.com/LOjnyHf.jpg
I cleaned it no real change, so I guess I got a problem in the rear-end. Going to pull the cover tomorrow morning and see what I find.
Now while I am in there, clean all the crud off the tone gear check for:
play in the carrier
missing/chipped teeth on tone gear
crud built up on tone gear
Anything else I should be looking for?
Also just to clarify the speedo is rock solid up untill 35mph, after that it starts moving 4-5 mph and sometimes it will hold steady speed and then continue moving 4-5mph I've tested it up to 55mph.
Should have put this in the first post, but there is also electrical tape over the shift leaver where the overdrive light would be, going to peel that off and see if the light is blinking.