Engine/Transmission (1994 - 1998) oil pressure and speedo not working

[SRay]

Hello all, my buddy has a 1998 12v that he just recently purchased. The truck is a bit rough but he has plans to restore the truck.



I haven't done any of these repairs yet so no experience yet myself.



When he's stopping at the stop sign, he feels a clunk and the oil pressure gauge goes down then back up. I'm not sure if they're both related or the truck has more than one problem which is likely.



I haven't driven the truck yet myself to know. This is what he's telling me.



Also the speedo gauge doesn't work and not sure if it's the sensor or... ?



Shawn

 

[Missouri Mule]

The speed sensor is on the diff for the 98's.

Loose wiring/connections for the oil pressure gauge or the gauge itself.

Clunk ?

 

[fest3er]

The clunk is the rear ABS engaging because the system *thinks* the speed suddenly dropped from somewhere above 6 MPH to 0. Most likely there's crud built up between the tone ring in the rear diff and the sensor; this causes the voltage from the sensor to drop below the CAB's detection threshold. Equally likely is that, if an Abbott or TruSpeed speedo correction device is or was installed, the splice connections are slightly corroded. Another possibility is the ground connection from the CAB to the body (on the fender between the PDC and the hinge) needs to be cleaned and retorqued.

The oil pressure dropping and returning is a wore-out sender; $30 or so from a Cummins shop. If it's like my '98, be sure you install the brass adapter first, then install the new sender.

 

[Missouri Mule]

That's right fest3er sender not gauge which I appparently had on my mind.

 

[fest3er]

That's right fest3er sender not gauge which I appparently had on my mind.

Understandable when you see twins everywhere... .