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I don't know enough about this transmission to be able to diagnose the issue I'm having. It's kind of difficult to explain but I will do my best. It seems like my torque converter is trying to lock up when it should not be. This normally happens just after shifting into reverse but I've also experienced this in 1st when I've stopped at a light or what have you. I've monitored torque converter clutch and torque converter slip with Forscan and I've seen that the torque converter clutch doesn't appear to be causing what I've described. When this happens the TCC stays steady at zero. The TC slip is a different story. I've watched the TC slip go from slipping @ 650 roughly and drop to near zero slip. If I hold the brake well enough I can keep the truck from getting away but it sometimes stalls, otherwise when this happens the truck tries to add fuel and push through the brake. I would grately appreciate any experience or productive suggestions. I have saved a couple CSV files that I could upload or send to someone to chart if that might help. Thank you all in advance.
TC Slip dropping to zero is showing it going into lockup as you suspected.
I have read that TC lockup is kept off by fluid pressure, meaning low fluid can cause it to go into lockup.
Check your fluid level on flat ground with it running in Park while warm.
Absolutely true.
If the fluid level is fine, the next check is to get a 0-350 PSI gauge with a 1/8" NPT thread to check line pressure when this happens. The test port is on the driver's side of the trans, just above the pan, towards the front of the trans.
Thank you Jason. Fluid is definitely low. Will refill this weekend and report back after a few days of driving. I normally only drive this truck a couple days a week to keep the mileage low, just went over 150K.
Mark, the location description you provided for the test port sounds like the same spot the trans temp probe is supposed to go. Is it possiple to put a Y or T adapter there to have both a temp probe and a test port?
The temp probe has to be in the fluid path. I don’t see how you could do that while also incorporating a Tee. At least not with your current probe that’s meant to direct install into the port.
You could purchase a wire style temp sensor which seals with a compression fitting to accomplish this task. The wire probe tip would need to be installed deep enough to be within the fluid path while the pressure side is on the 90° Tee fitting. But I wouldn’t really recommend this due to more potential leak sources or probe durability in a vehicle application.
For reference:
Realistically though you shouldn’t need to read line pressure all of the time. You could temporarily remove the temp sensor while doing pressure test.
I read the built in trans temp from the PCM using an Edge CTS.
Thanks guys. Both are good points and I figured as much. The reason I asked is because I'm a little concerned about opening up that port once the appropriate fluid level is attained. Can it be opened without fear of fluid shooting out of the open port or is it only recommended to open that port when the fluid level is down?
I don’t think you’re going to need to test the pressure after resetting the fluid level but we shall see.
Mark will have a better answer but I’ll take a shot at it.
Opening the port for the swap shouldn’t be a problem because it should be within a circuit that’s not directly open to the pan. I expect it to drain some residual ATF out of the passage but not excessively. Besides, you’re going to work “quickly” to swap over to the pressure gauge and not leave it open for days.
Take care if using Teflon tape. You wouldn’t want any pieces to get into the VB.
Just don’t remove the plug with the engine running!
You could lose as much as an ounce by removing that plug. Usually, it's far less than that.
DO NOT USE TEFLON TAPE!!!!!!!!!!!!!!!!!!!!!!!!!!! This is a dryseal thread, it does not require any sealant. If you get the smallest piece of teflon tape loose in the transmission it could plug an orifice or stick a valve, and then you need a new transmission. DO NOT USE TEFLON TAPE!!!!!!!!!!!!!!!!!!!!!!!!!!!
Have I mentioned DO NOT USE TEFLON TAPE!!!!!!!!!!!!!!!!!!!!!!!!!!!
Ok I think the most important thing I read was DO NOT USE TEFLON TAPE. And I am so grateful for that advice. It is also very reassuring to know very little fluid loss will occur from the quick opening and closing of that port. Now I did add some fluid and drove the truck this evening and I experienced none of the symptoms I previously described. I'm not sure one outing is enough to say the culprit has been discovered but I'm very hopeful. Thank you guys.
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