We occasionally get this question about early Hydramatic (pre Turbo Hydramatic). What fluid should be used? Wiki has an interesting piece on the evolution of Hydramatic fluids, so if you would like to learn more, we have provided a link below.
Did you know that some shops back in the day used engine oil for trans fluid? That is why you will see some transmission that appear dark and sludge filled internally. And this is one reason GM started developing a better fluid and started using a red dye fluid to determine what the fill was.
Why do we recommend DEXRON III?
Can you start using DEXRON III instead of older versions of DEXRON or Type A? Probably. Using DEXRON III will not fix a broken transmission. And because DEXRON III may clean out the debris that is keeping things working, it is possible that a fluid change might cause transmission issues to get worse. But keep in mind that a rebuild will correct everything and provide years of service. Starting to use DEXRON III can help older seals regain some elasticity. Remember, drain the coupler and pan for best results. And, as before, if you have questions, drop us a note via email.