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

[Shawn Wright]

On 6 Nov 2003 at 8:28, Roger Brown <r.c.brown at ieee.org> wrote:

> 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.

It is this part that caused me to consider carefully the choice of oil for my Vanagon
transmission, which calls for a GL-4 *Hypoid* oil. I have never found such an oil, and
even Redline's own description of MTL and MT90 leave this issue open to debate -
from their website:

"Typically, the use of a GL-5 lubricant in a synchromesh transmission will shorten the
synchronizer life by one half. The extreme pressure requirements of spur gears and
helical gears found in transmissions are not nearly as great as found in rear-wheel
drive differentials. A GL-4 lubricant provides adequate protection for most manual
transmissions, unless a unique design consideration requires the extra protection of
a GL-5."

Here I am assuming that hypoid and helical gears are the same, or at least their EP
requirements are similar. Many repair shops and even VW dealers, including the
shop that replaced my ring and pinion, use GL-5 oil, I think because they would
rather protect the R&P at the expensive of the syncros (and shifting quality).

My R&P failed after I ran with Redline MTL for less than 20k kms. Coincidence?
Perhaps, as it did have 200k kms on it. But to be safe, I chose Amsoil TGR, which is
the only gear oil I could find that claims to be GL-2 through GL-5, by using EP
additives that are safe for syncros. Another 20k kms on a brand new R&P, and my
trans is once again noisy, so I plan to drain the oil and investigate.

All of this is only meaningful to Vanagon owners, many of whom seem to use MT90
(MTL is too thin I now know...) without problems. But I wonder... why does VW call
for a GL-4 Hypoid that does not seem to exist (even at the dealer)? For those with
fwd VWs, I can highly recommend MTL - my '85 Jetta has 482k kms on it and still
shifts like a dream using MTL.

--
Shawn Wright
http://Zuiko.sls.bc.ca/swright
'88 Westy 375k
'85 Jetta D 263k
'85 Jetta TD 482k (retired)
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