[Vwdiesel] Fw: Transmission ---- 5 speed manual ( changingoil )

[Roger Brown]

Scott Alexander wrote:
>
> What's the difference and what happens if one does?  I ask because it'll
> be easier to convince my buddies not to just put in whatever is lying
> around and because if I find myself with a leaky transmission in the
> middle of nowhere and only GL-5 available, it makes it easier to make
> the decision on tow, drive a short distance and change the oil as soon
> as possible, or drive home and switch the oil when fixing the problem.

Two things at work with a GL5 oil:

1. Its designed for helical cut gears, that have sliding contact, and it has extreme pressure (EP) additives to make it slippery and also to prevent the oil chains from shearing.

2. These additives can be corrosive to certain "yellow metal" parts that are commonly used in manual transmissions, see:
	http://www.google.com/search?hl=en&lr=&ie=ISO-8859-1&q=Yellow+Metal+GL-5+GL5

So the problems arise from both the above.  #1 will cause the synchros to slip for a longer period of time and you shifting will be sluggish, more grinding of gears.  A GL4 oil will have a high coefficient of sliding friction (since its designed for
straight and bevel cut gears that don't slide past each other in contact) and this lets the synchro rings get a better bite and spin up their gears faster.  #2 may case things like the brass and bronze bushings and synchro rings to corrode over extended
periods of exposure.  If a manual tranny is rated for GL4 or GL5 oil, this means it doesn't have susceptible alloys inside, so #2 is not an issue, but #1 still applies.  Its likely that almost all "modern" transmissions ('70s onward) can tolerate GL5 oil.

So, GL4 oil in all my manual trannys that spec it:
	http://4crawler.cruiserpages.com/Diesel/ForSale/ShiftLinkage.shtml#FAQ20

--
    Roger