My grand marquis (98) has a hard time shifting or slips around 2 an 3 gear an at same time when cold runs fine but warmed feels heavy
Most likely the clutch pack in the trans are worn out. If the fluid is burned you could have a qualified technician flush the transmission with new fluid to see if that helps.
Well the tran fluid has been replaced an didn't help.
Was thinking might be a tran solenoid.
Trans solenoids usually fail at any temp. A good transmission can diagnose it for you at a reasonable cost. But i suspect it will need rebuilding.
How would I diagnose it
It's probably shot, but try Lucas transmission additive, just in case it's sticky valves. I've seen miracles happen.
I've put some before. After the first change. I put the entire bottle. An rest with tran fluid.
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