I have a 938g wheel loader 4ys300387 with a 191-8 transmission code with cat et hooked up have no transmission output speed input. The tractor has delayed shifting when working. The output sensor has been replaced but still shows no input. the tourque converter outlet pressure is below spec are these two issues related or am I dealing with two seperate issues?
Have you tried troubleshooting the Code.? It could be that you have a wiring problem.
I checked the ground side with good continuity back probed the sensor and did not get any ac voltage coming out on the green wire may need to check it in frequency mode to see if I am getting anything. Is the internal gear able to be spun with a screwdriver or is it a fixed gear that moves with the transmission?
I am just curious if there is a correlation between the output speed sensor to the tourque converter outlet pressure because I have a tech dead set on pulling the valve body off to check the orfice before correcting the current code first
I haven't done much with loaders in some years but seem to remember the input on the transmission can be monitored to check the output speed on the torque converter. I wouldn't think the output speed on the transmission would have anything to do with the torque converter unless it sensed a mismatch between input speed and output speed. A low torque converter outlet pressure in my experience can cause torque converter overheating.
Did you try that troubleshooting procedure I attached in post #2.? It might just throw up something that you hadn't considered. The gear that activates the sensor only turns when the machine is moving. I would say you are dealing with two separate issues. The erratic speed sensor will only cause the shifting points of the transmission to be messed up AFAIK. I'd fix the sensor issue first then move on to the converter.
Thank you guys for the help I am off work for the weekend but will follow the tests for the sensor and try to resolve that issue first. The loader has reman transmission in it with only a couple hundred hours on it so I will resolve the speed sensor issue first then test my pressure at the outlet. I’m not 100% the pressure is incorrect was basing it off another tech checking it. But it’s just a delayed shift is what it seems like to me so I have a feeling the sensor is playing a part.