34 What transmission fluid should I use (manual cars)? Why is it important for racing?
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This article is from the VW Performance FAQ, by with numerous contributions by Jan Vandenbrande others.
34 What transmission fluid should I use (manual cars)? Why is it important for racing?
A:If you use a transverse engined car at a track for speed
events (as opposed to a parking lot autocross), you may
actually be in a corner long enough to slosh oil clean
away from the pickup, with possible bad results (please
don't ask how I know). The real solution is to get a
baffled oil pan, but synthetic oils will do better than
dino oils in this situation.
As far as I know, most/all water cooled VW transmissions
require gear fluid with an API rating of GL-4 (MIL-2105).
The recommended GEAR viscosity hovers around 80W, 75W-80
or 75W-90 Note that 75W-80 GEAR oil is equivalent to
10W30 MOTOR oil, but it is NOT recommended to use motor
oil in gear boxes, even though some Japanese cars do so
any way (has to do with shear strength). GL-5 oil is made
to lubricate gears (like in a differential) and may cause
premature wear on brass synchros.
NOTE that GL-5 is recommended for the *differential* on
some AUTOMATIC VWs and on some manual transmissions.
However most VW *Manual* transmissions need GL-4. Check
your user manual or VW.
Quality of the gear oil makes a HUGE difference in
shifting. I have personally tried Castrol (HORRIBLE),
SWEPCO (Better), VW gear oil (good, I suspect that they
use a synthetic in some cars), and Redline MTL (best so
far). Others seem happy with Mobil 1, Synthoil, Spectro,
etc. How these oil affect transmission life is unknown to
me. Note that MTL is rated 75W80, while their newer
product MT90 has a rating of 75W90 which may be closer to
the required viscosity of your transmission.
VW also sells synthetic transmission oil (at US$20/liter)
which is probably one of the best oils to get.
Most VW transmissions use somewhere around 2-2.5 liters
of oil. Before you drain, make sure you have something to
catch the oil (an old jumbo coffee can is perfect). Open
the side fill hole first, because you'll have to fill it
up to either the fill hole or BEYOND. You'll therefore
either have a little bit leak out or 1/2 liter gush out.
To drain (the rest), unscrew 17 mm allen plug at the
bottom of transmission. To fill, either unscrew
speedometer cable or use the fill hole on the side. Some
VWs require the level of the oil to be just so that some
drips out of the fill hole, others (some A2 Golfs/Jettas)
require an additional 1/2 liter on top of that. That's
why it's a good idea to catch the old stuff and check the
fill hole first.
[NOTE: Some VW User's Manuals apparently do recommend GL-
5 in some transmissions, so check first! blu@cellar.org
seems to be doing ok with Redline GL-5 after 100kmiles in
his car. However, Peter Tong had bad experiences with
GL5: he could not get out of 3rd gear with GL-5 oil.]
[NOTE: One recent posting by (Paul Keller) blames his
transmission failure on MTL, and claims that Redline
recommends MT90 only for VWs. At this point it is unclear
to me whether MTL is to blame, and whether using MT90
would have made much of a difference. Keep in mind that
he is one of two so far which blame Redline out of many
who have had no problems so far.]
TIP: Glue a small round magnet on the outside of the
drain plug. They can be bought cheaply at electronics
stores, and it will attract metal particles that may
damage the transmission. Older VWs used to have magnetic
drain plugs, but VW stopped using them for some reason.
Some newer VW trannys now have this magnet BUILT in
permanently.
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