hydra-matic transmission fluid

[48streamliner]

Hi all!

Just bought a 48 Streamliner that last ran about 5 years ago. Any thoughts on whether I should change transmission fluid in the hydra-matic before even trying to run and move it, and what the best modern fluid is to use? Thanks! David

[Larry]

I knew we had addressed this a long time ago, so started hunting for the information again.

I had a number of '54 Pontiacs and believe we changed the fluid with 10wt engine oil... really! However, there are answers from others that are even better.

One past response was: From the '48 - '53 Hydramatic Transmission Manual, "use only Automatic Transmission Fluid type A, qualification number, AQ - ATF."

And then from our 1949-'52 Tech Advisor- who knows all the early Pontiacs inside and out- recommends Dextron II, and to stay away from the Type-F Ford stuff.

An automatic transmission of any type needs clean, thin fluid to make it work as a hydraulic unit. In actuality almost any hydraulic fluid will work, but the differences come from the abilities of certain fluids to withstand heat, stay clean (while also cleaning), and how they react to different rubber and seal materials.

The Dextron II is the most recommended fluid today for these older cars with a Hydramatic.