Hi all. Been looking the forum over a bit, decided to join cause I see a lot of stuff being discussed that I involve myself with, "for fun".
New truck, to me. 99 C3500 dually 7.4l auto trans.
Speedometer reads while parked. Goes up as high as 50mph while revving the engine in neutral, while parked. Drop it in gear, reads 0.
While driving, it reads pretty normal under a load. When coasting or light throttle speed moves around a bit and shifts real late, even hunts gears under light throttle near normal shift point.
To me it seemed like a bad ground, so I cleaned and tightened all ground straps I found, even added one from trans case to frame. No change. I don't think it's a bad cluster because the scanner verified the speedometer. Also changed out the VSS, no change.
Parts that were thrown at it by previous owner and mostly verified by me:
ECM
engine harness
TPS
MAF
EGR valve
Distributor
VSS
Trans internal harness
I verified the ground from the neg batt to fender was solid, and the 2in1 strap near the starter from frame to body and frame to back of cyl head was re seated.
I'd love to hear opinions about this issue, or anything else if you choose...
Dennis
New truck, to me. 99 C3500 dually 7.4l auto trans.
Speedometer reads while parked. Goes up as high as 50mph while revving the engine in neutral, while parked. Drop it in gear, reads 0.
While driving, it reads pretty normal under a load. When coasting or light throttle speed moves around a bit and shifts real late, even hunts gears under light throttle near normal shift point.
To me it seemed like a bad ground, so I cleaned and tightened all ground straps I found, even added one from trans case to frame. No change. I don't think it's a bad cluster because the scanner verified the speedometer. Also changed out the VSS, no change.
Parts that were thrown at it by previous owner and mostly verified by me:
ECM
engine harness
TPS
MAF
EGR valve
Distributor
VSS
Trans internal harness
I verified the ground from the neg batt to fender was solid, and the 2in1 strap near the starter from frame to body and frame to back of cyl head was re seated.
I'd love to hear opinions about this issue, or anything else if you choose...
Dennis