Okay, so I've got a '99 Firebird, 4L60E. After about 30 minutes of driving and acting normally, it will simply drop out of TC lockup. Trans temps are right about 195-200, which is about where the engine runs, so I don't think it's getting too hot. Trans doesn't act like it's slipping at all, no harsh shifts, and hasn't thrown a P1870, trans component slipping. It has plenty of fluid in it after a recent top-off (was about a quart low, no leaks that I've seen). It WILL go back into TC lockup when climbing a slight incline such as an overpass, but as soon as it gets back to level ground, it again falls out of TC lockup.
Any ideas? I am guessing that it's either a problem with the TC itself or the TCC lockup solenoid. If there's something else I should be looking at, please let me know.
I also have a '99 GMC Jimmy with the same trans, but when it falls out of TC lockup I generally start to get harsh shifts and a P1870. This only happens on hot and humid (80+ degrees, 40%+ humidity) days. Spring, fall, and winter we can drive for HOURS in stop and go traffic and have no issues. Summer is the problem. I believe it's heat related, and have a trans cooler that I intend to install, but if there's something more I should be looking at I'd love to know about it.
Thanks for your help guys/gals!
Any ideas? I am guessing that it's either a problem with the TC itself or the TCC lockup solenoid. If there's something else I should be looking at, please let me know.
I also have a '99 GMC Jimmy with the same trans, but when it falls out of TC lockup I generally start to get harsh shifts and a P1870. This only happens on hot and humid (80+ degrees, 40%+ humidity) days. Spring, fall, and winter we can drive for HOURS in stop and go traffic and have no issues. Summer is the problem. I believe it's heat related, and have a trans cooler that I intend to install, but if there's something more I should be looking at I'd love to know about it.
Thanks for your help guys/gals!
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