Re: Transmission fluild

Posted by Bobby On 2012/9/16 19:21:45

Uh, oh..the Ultramatic fluid debate..

First, it's Type A that's spec'd by PMCC. Some say that it is still available, but I haven't found it.

So, anything other than "A" isn't going to duplicate "A". It would be interesting to hear from Howard which ATF comes closest to matching the slip/friction characteristics of "A".

All that said, my original '54 with properly adjusted and maintained Ultramatic works best with Dex III. It is smooth and quiet, shifting as spec'd, even when cold...I'd go so far as to say the shifts (esp. when warm) are seamless. Like many, I started with 'F', and found it produced noticeably jerky shifts and clunked loudly when downshifting when cold. When I drained and refilled (converter, too) with Dex III, this stopped. Since then, I have used only Dex III (about 20 years), with no problems. In the P/S unit, and P/W reservoir, too.

You can try either trans. fluid, there's no risk of damage to the unit..just make sure you drop the pan and get the converter, too..and while you're doing a trans. service, consider removing and cleaning the valve body, which is part of the unit, but easily detachable...the little passages in there are frequently the place where gunk and debris collect and create problems. Just fill properly, run it thru the gears a few times, and check the level when the car is in neutral. If a drive indicates that she's shifting rough, you can always try the other fluid.

As an FYI/FWIW, I've driven Hydramatics and Dynaflows from the same era and the Ultramatic is a superior automatic in terms of smoothness and quietness, when properly set up and maintained.