it only shifts hard when the clutch fan is cold.after the fan gets quiet it shifts just fine.a friend of mine has a 99 with a 4.3 and his is quiet all the time.
When the engine is shut down after reaching normal operating temperature, the silicone fluid within the clutch transfers from one chamber to another. It usually takes approximately 2-4 hours for this to happen.
When the engine is re-started, the fan spins at approximately 80% to 90% of water pump RPM causing it to “roar”. As the silicone fluid is redistributed evenly within the clutch, it gradually disengages and the fan begins to free wheel causing the "roar" to decrease. The fan will continue to free wheel until the air temperature at the thermostatic coil on the clutch reaches approximately 150F. The internal components of the clutch gradually redistribute the silicone fluid and begin to engage the clutch.
As the clutch engages, airflow is increased across the radiator allowing it to dissipate more heat. When airflow temperature across the coil reaches approximately 195F, the clutch becomes fully engaged and the “roar” becomes noticeable again. When the air temperature at the coil decreases, the clutch starts to disengage, and the cycle starts over. Think of the fan clutch as a “temperature regulator” or “thermostat” for the radiator.
Hope this helps clear up the way your fan clutch works and your friends 99 clutch fan sounds like its worn out
As for your transmission shifting hard, if you read the link. It would explain what the "Adaptive Strategy" which has been in use since 93, but in a basic form compared to what it is today. What it does is it makes adjustments in line pressure to obtain consistent shifts and helps to increases the life of the transmission. As clutch material wears, clutch pack clearances increase, the timing of apply can change resulting in shift overlap. Shift overlap is the time it takes to complete a shift.
I would have an occasional harsh 1-2 shift and a clunking 2-3 shift, both have disappeared and now shifts smooth as can be when i service the transmission. I think it takes time for the adaptive learning to fully work because not all shifts are adaptable. But if you have a 1-2 shift that is hard all the time, that could be a different story. The first thing is to have it scanned for codes. Some trouble codes will default the transmission to high line pressure, which will give harsh shifts.
In your case, I would check the transmission fluid level when hot and condition. If the fluid and filter is dirty, the PCM will adjust the current to the pressure control solenoid to increase the line pressure giving you a hard shift and then will adjust for a softer shift on the next shift patterns after you start driving.
Hope this helps and keep us posted.
Molson02536
Thanks you have cleared up alot for me.