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That was an interesting article, Gary - thanks for the URL! I'm not pointing out the following with the idea of rebutting it, just to note that a vintage-SAAB transaxle is in some ways an unusual beast with a couple of specific lubrication requirements that weren't addressed in the article:
--Ball bearings and the need for cleanliness: The shafts in a VSAAB transaxle run in ball bearings; this is different from most transaxles, which use roller bearings. Ball bearings have proved themselves well, but because their point of contact is much smaller (one point on the surface of a sphere rather than the length of a roller) it's especially important to keep the innards clean; it doesn't take a very big piece of grit to jam up this tiny contact point. That's why it's so vitally important to change your transaxle oil frequently -- you need to drain out any gunk and suspended particles. I figure the key to this is not what TYPE of oil you use, but simply how OFTEN you change it. In other words, an oil whose primary benefit is "longer life" may not provide any advantage in a vintage SAAB transaxle -- you're going to have to change the stuff so often anyway that you won't get to take advantage of it.
-- Bearing lubrication and the need for "flingability": Several important bearings in the transaxle case are lubricated by oil that's flung off the gear teeth and caught in little cups that stick out into the transaxle interior, where the flung oil "rains down" into them. The way I figure it, an oil that's too thick or too sticky (i.e., does too good a job of adhering to the gear teeth) may not get flung away enough to reach these cups, and as a result the bearings won't get the amount of lubrication they need and will wear prematurely. (And they're a flaming pain to replace!)
This could be a tricky issue because I'd think that most lubricant manufacturers would WANT to design their lubricants to adhere to the gear teeth -- after all, that's the part they're trying to lubricate, so wouldn't you want the lubricant to stay there? Well, in the case of a vintage-SAAB transaxle, not necessarily!
So, as I said, none of this necessarily invalidates what was in the article Gary cited. But it does show how the peculiarities of a SAAB transaxle may require different lubricant properties than those needed by the "average" gearbox. I figure that in this type of situation, experience is the best guide -- but of course none of us want to get that experience by wearing out a lot of transaxles!
posted by 204.76.11...
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