Torqueflite Help

My 1972 Road Runner (Torqueflite A-727 Automatic) transmission slips (high RPM without any power through the trans) but only in high (third) gear.
This happened after I noticed a trans leak while driving (after storing it for the winter).
I added more auto trans fluid and there is no more noticeable leaks.
It seems not to slip in first or second gear and up shifts/down shifts fine.
Would a complete fluid replacement help/cure this or do I need a rebuild?
Is it possible I cooked third gear only by running low on trans fluid.

Help ... this is my first Mopar automatic trans and I'm not sure what to do.
Thanks!

Slipping in 3rd gear is usually a problem in the front clutch but it could also be a clogged filter so it's worth a try to pull the pan and have a look-see. Running with low fluid could have fried the clutches.

If a fluid/filter change doesn't help it's due for an overhaul.

Quote:

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Slipping in 3rd gear is usually a problem in the front clutch but it could also be a clogged filter so it's worth a try to pull the pan and have a look-see. Running with low fluid could have fried the clutches.

If a fluid/filter change doesn't help it's due for an overhaul.

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