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Old January 14th, 2008, 14:34   #355
Join Date: Jan 2008
Location: SCal
TDI(s): 1997 Passat

Originally Posted by AndyH

I'd like to request that we include the year and transmission (especially if not the transmission the car came with when it was born). We're all commenting on how a certain product feels or performs in our car, but this info is basically meaningless with out knowing what the hardware is.

Tied to my first request/comment are these cautions:

- The first choice for any fluid should be one that meets the OEM required specifications and viscosity for your specific piece of equipment.

- Before one can select an alternate product, we must know the OEM requirement. The fluid properties, characteristics, and specifications were based on the engineering of the specific piece of hardware. Different transmissions will probably require different fluids.

Here’s a quick summary of what can happen if we experiment without proper info.

- A gearbox that was being monitored with oil analysis and vibration analysis failed catastrophically
- The gearbox was replaced with a new unit, refilled with fluid, and put on-line
- The replacement gearbox failed after two days of service
- The gearbox failed – twice – because ISO 680 viscosity fluid was used instead of the OEM recommended ISO 320 gear lube

Keep something in mind here – ISO 680 IS a recommended fluid for this gearbox – for a specific range of temperature and duty conditions. This was NOT a case where the operators decided to second-guess the engineers.

You can read the full article from this month’s “Practicing Oil Analysis” magazine on-line at OilAnalysis&title=Confirm%20OEM%20Recommendations% 20-%20Replacing%20the%20Problem%20May%20Not%20Remove% 20the%20Problem

Bottom line for us TDIers: Those of us with older cars – with transmissions designed during a time when the industry was using ‘universal’ fluids – should stick with the recommended 75W-90 GL-4 synthetic. If we select a GL-5 fluid, we can expect synchronizer problems from either friction modifiers (slipping) or extreme pressure additives (sticking, corrosion). If we select lower viscosity fluids than recommended (such as G052726A2, Synchromesh, or ATF), we can expect higher rates of wear due to lower film strength – higher wear means more friction, more heat, earlier fluid failure, and shorter seal life. If we select higher viscosity fluids, we can expect a drop in fuel economy, more generated heat because of the extra work required to overcome the resistance of the thicker fluid, stiffer shifting both hot and cold, and sticky synchronizers as a start. We’ll also have increased rates of wear and can have early bearing failure because the heavy fluid can’t get into narrow passages as well as the proper fluid.

The ‘Lesson Learned’ from the Noria / Practicing Oil Analysis article is this: “Recommended lubricants should also be confirmed if in question. Case in point: this gearbox suffered a level of wear that could have been avoided. It is safe to say that much useful life was lost from this unit to this common error. While operating conditions may occasionally warrant the use of a lubricant other than that recommended by the manufacturer, the OEM recommendation should be strongly considered as the starting point. Careful testing and documentation should be conducted prior to making a viscosity change in any piece of equipment.”

“While it is widely understood that using a lubricant too low in viscosity will result in insufficient lubricant film, it is also important to understand that using a lubricant too high in viscosity can produce similar problems. In this case there was an apparent loss of lubricant film due to the reduced oil flow through small passages, which were designed for a lower viscosity lubricant.”

Well said! But... what do you do if the Manufacturer VW changes it recomended oil/viscosity wildly?

Old recommend for 02A = G50 vis@100c 15.6. Good old GL-4
New VW recommend for 02A = G052-726-A2 vis@100c 6.3 GL rating unclear.

You make perfect sense to me when you say stick with the factory oil and that both too thick and/or too thin can cause damage. Appearantly its not so clear to VW. Or are we merely chasing our tails because VW wishes to consolidate its oils at the possible expense of the longevity of our older trannys?
StevenM is offline   Reply With Quote
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