http://www.peachparts.com/shopforum/diesel-discussion/308727-what-proper-fluid-power-steering.html

and many other links in my post in that thread http://www.peachparts.com/shopforum/2833903-post24.html

I imagine that the "ATF" specified in old MB manuals for use in PS pumps was Dexron II --I don't think Dexron III had been invented yet. The Gulf ATF MX listed on schedule 236.3, if you look at its spec sheet, is listed as a Dexron II ATF. I would speculate that any Dexron II ATF would work as PS fluid in a W123 or W126 with the OM617a engine.

Whoop. My bad. I got my threads mixed up. So sorry. :stunned:

I would imagine that your speculation is correct. Note Ive never said that ATF wont work - I even said that ATF is nice because you can get a good syn in there. Someday I may put syn ATF in mine just for fun. If a line goes bad, its 30 years old... Ill replace it.

But the thing with Dex III (which is no longer a fluid, as there is no such thing as a dexron license anymore, but we can assume that a D/M fluid is as good as what Dex III is), is that while it may well be back-speccable to Dex II for GM (and other) ATs, the question really becomes if it is suitable for other applications.

Its kind of like the newest Dexron, VI. Dex VI has roughly the same starting viscosity as we would see on Dex III after some mileage. It is a more stable fluid, has some great properties. It is suitable for use in AT applications where Dex III was specified... At least to a point. Yet we have seen that it does not carry the latest Allison Transmission specs because of some concern with compatability with certain elastomers. Similarly, it is not intended per GM to be used in manuals as an MTF. So it may well be the greatest ATF in the world right now, but in applications tht it was not intended for, there may be issues...

there is no atf anywhere that is intended for use in a manual gearbox. it's far to thin and watery for manual gearbox use.

unless you live in extreme arctic climate where it stays far below freezing year round, then manual gearboxes can and should use atf. but that's a specialized situation.

How different is the PS reservoir and pump system on an older 617 W126 as compared to the W123? I can imagine that there is a difference in steering box, ratios, etc., but the actual pump and hardware of importance in a hydraulic system???

Youre joking, right? I have a BMW that states dexron ATF as its fluid in the manual gearbox.

And there are a ton of cars of all makes that utilize ATF as an MTF.

It is in no way a specialized situation.