1992 f250 abs light on and higher than usual rpm

[UslAura1]

Hey folks, about 1 week ago my rear abs light came on, and since then my mpg is terrible and my rpm at highway speed as gone from 2000 at 60mph to 2300-2400 at 60mph, any idea what can cause this?

1992 f250 2x4 7.3 idi with 4.10 gears

 

[IDIBOBS]

Time to open up your rear diff. I’d bet your time ring has an issue.

 

[rreegg]

You can also pull the rabs codes/flashes.

should be same as this: https://www.f150forum.com/f10/how-retrieve-abs-trouble-codes-62106/

 

[Nero]

Hold the phone fellas...


Is it an auto or manual?

 

[IDIBRONCO]

Hold the phone fellas...


Is it an auto or manual?

Very important question.
Assuming that it's a E4OD, whatever caused the ABS light to come on is also probably giving a bad signal to the transmission computer. The torque convertor isn't locking up, but it appears to still be going into overdrive. If you get the ABS light taken care of, the transmission will probably straighten out too. Again, that's all assuming that there's a E4OD in the truck.

 

[UslAura1]

yeah its a e4od

 

[Nero]

Is your OD light flashing? If it is, that means you have fault codes for the transmission. Pull the codes.

 

[UslAura1]

Nope, only the abs light on the overdrive works as it should, i will try to pull the codes from the rabs this weekend and give updates to you

 

[BeastMaster]

Doesn't the VSS sensor feed both the speedometer and the ABS?

Does the speedometer give steady readings?

How easy is it to tap into the VSS pickup lines at the PSOM or ABS and look at them with an oscilloscope?

( I guess you have already serviced the VSS pickup by now. If not, it is magnetic, and may be covered in wear debris from the wearing of the differential gears ).