GL1500 air shock fluid change

IceRacer, the reason you'll see ATF and SS7 kinda used interchangeably is that mother Honda didn't have a Suspension Fluid product for sale when the 1500 was introduced. ATF (Dexron III, at the time) though not specifically controlled for CPS and viscosities provided "close enough" properties for these applications (forks, shocks, etc).

I'm sure that Honda wanted to provide a better and more-controlled suspension, which is why Honda spec'd (and branded) suspension fluids became available (I'm sure that sales in the aftermarket were also attractive). In my personal view, I believe that the suspension guys at Showa started pointing out that their technology was better supported by purpose-made, specification-controlled fluids...

To shorten this up a bit, if you look at the OEM manuals for something in the early years of the GL1500, you'll see ATF/Dexron III specified for several hydraulic and damping uses. A little later on ('95+ for certain) you will see SS7 specified in the field service manuals for these tasks. (... "SS" for "Showa Suspension?" SS7 is supposed to be about a 5w suspension fluid (actually, measured at about 3.5w) and the SS8 is supposed to be a 10W (actually, measured at about 7.4w), which aligns quite well with the early Dexron III that mother Honda was using as a service fluid.

One thing that could NOT have been foreseen at the time that ATF was being specified is that several of the newer ATFs (ie: MerconV spec, etc) have specific "sticky" and "friction" enhancements that may not play well with our suspension components. the Dexron II-III era stuff was made with great dispersive characteristics and great lubrication that could handle some serious temperatures, but the trannys that these worked in had large clutch areas and were "ON/OFF" type of clutches that stopped the gearsets by the raw power/friction of the bands. These newer (Mercon V) type things actually work at "soft-engaging" where the fluid has some fiction properties in thin-films to sorta "pre-engage" as the bands come proximal to the drums... (not withstanding these new fluids have AWESOME temperature handling too!) -- So the thin-film non-pressurized lubrication that we would rely on from Dexron II- III in our suspension applications would not be provided by the GenIV-V (Mercon V example) fluids...


For the OEM air shock, the fluid is for lubrication and to "adjust" the compressible air space (higher fill amounts increase the relative compressive spring rate for a given staring air-charge (psi) ). The OEM air shock on the 1500 doesn't have any 'valving' where viscosities become critical...

... All in all, a rather long way of explaining that either ATF (Dexron III slippery-style) or the Showa SS7 fluid will be fine for refill, and why you may see either or both referenced on postings...