Tranny problems

Have a 1987 420SEL with 170K miles. Transmission problems are new to me so I'd like a few pointers before I take the car to a shop.
Occasionally the transmission doesn't want to upshift from 2nd to 3rd or
from 3rd to 4th. It may work fine for a few days, then start giving upshifting problems again. This problem often is brought on by making a right turn. Weird, huh? I can sometimes cure the problem temporarily by stopping, then shifting briefly into reverse, then going forward again. Once the problem starts, say by not upshifting from 3rd to 4th at freeway speed, it won't cure itself. I have to stop and do the reverse trick.
Any suggestions would be appreciated. I don't know if I'm ready to pay a large transmission repair bill for this old car.
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Suggest you have the transmission fluid and filter changed, including draining the torque converter. That will eliminate the most obvious cause of transmission problems. If this doesn't solve it then it's probably on to servo pistons.
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George: If you haven't already changed the tranny fluid..its worth a try.
Larry
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The transmission leaks and I top it off every few weeks. Does that count as a fluid change?

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The filter also needs to be replaced. It may be clogged with gunk. Peter

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No, because the dirt doesn't leak out. It's probably acting up from the dirt that's been introduced when you add fluid, so have the leak fixed as part of the service or you'll never be done with the problem.
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