Summary
The mainline pressure is varied when the computer operates a pulsing solenoid that regulates a small amount of fluid pressure on the end of the main pressure regulator valve. This valve controls the mainline pressure. If pressure is too high, the clutches engage quickly and firmly, which is what you want during full throttle shifts but not during partial throttle low-load operation. I doubt if the problem is with the solenoid or the regulator valve, as this would cause all shifts to be either firm or soft. The problem is more likely related to the computer control system.
The computer varies the solenoid operation by monitoring several sensors such as throttle position, engine and transmission temperature, shift lever position and vehicle load. Your problem only occurs after a highway drive, so I would look at something that is affected by the higher engine compartment heat. Using a scan tool to look at the computer data, record the throttle position and temperature sensor readings. Then display them in graph form. A loose connection at the sensors or at the computer, or an internal worn spot in the throttle position sensor could signal the computer to increase transmission pressure during the shift. This would show up on the graph.See the full content of this document
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Check Computer to Repair Cadillac
Backyard Mechanic / Jim Kerr
QUESTION -- I have a 1998 Cadillac Seville SLS. When we go on long trips with highway driving and then get off the highway to a stop sign, I find that when accelerating from a stop, the shift from 1st to ...See the full content of this document
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