Would heat be a factor affecting these issues? In other words, would the car shift ok when cooler and if one of the issues listed in your post was linked to my car, would heat be a factor in the car not upshifting? Does this make sense?:huh: :huh:
Yes, heat can affect the performance of the clutches. Without doing the standard diagnostics, I will list some possible causes:
1: as the oil thins, "leaks" at sealing rings can increase to the point that the clutch can not stay engaged. If this is the case, the trans needs to be dissassembled and repaired. There will probably be clutch housing damage or sealing ring damage requiring repair parts.
2:The valve body is made of aluminum while the valves are made of steel. They expand and contract at different rates and can cause the shift valves to stick as temps go up. This usually involves removing the VB and buffing the valves and bores. I can also be caused by metal parts impregnated into the aluminum. If that is the case, a new/rebuilt VB is in order.
3:The rubber sealing rings are hard/old and can no longer seal with thinner oil because of the heat.
Those are the most common. TimAT may chime in here with more info as well. To really get a good feel as to what is going wrong, we need to do a pressure test. Cold and hot. It is a realativly simple test but requires a guage, hose and misc stuff.
Does this answer your question?
BTW, does your oil smell burnt?
What color is the oil?