My 1990 Buick Regal has had a problem for sometime now(glad I found
this board). When the engine starts to get hot, and reach the near
mid-way point of the temperature gauge, the transmission starts
upshifting hard, especially when going into 2nd gear.
I had the transmission serviced with new fluid and filter but that did
nothing to help remedy the situation.
Could this be tranmission fluid viscosity issue? I figure the only
difference between a cold and hot running transmission is that the
fluid is "thinner" when hot, right? I've checked the fluid when hot
and it still looks good ie. not brown or burnt.
Which transmission is in the Regal ? If it is a 4l60e, it could be a problem
that is not really related to temperature, only appears to be. The problem
is with the torque converter clutch failing to engage, and the hard upshifts
are the transmission trying to compensate for "something slipping" with
OBDII, you get a service engine light, I don't know what OBDI will do.
Drive around next time in "3" instead of "OD", which should keep the TCC
from trying to engage. If the hard shift goes away, you found the problem.
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