Transmission Fluid, ???? Options

[mxhondarider832]

I have a '74 914 and the transmission is a little leaky and need to change the fluid, the book says to use straight 90w oil but I am having a really tough time finding it so I was wondering if there was a newer substitute that I could use. This is my first 914 and I am struggling a little bit and could use some help thanks

[Dr Evil]

From the redline website found here:
http://www.redlineoil.com/content/files/te...Tech%20Info.pdf

"GEAR AND SYNCHRONIZER WEAR PROTECTION
Most manufacturers of manual transmissions and
transaxles recommend an 80W or 90W GL-4 lubricant.
GL-5 gears oils which are required in hypoid differentials
are not used in most synchromesh transmissions
because the chemicals used to provide the extreme
pressure protection can be corrosive to synchronizers,
which are commonly made of brass or bronze. 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."

"DIRECTIONS FOR USE
Red Line MTL may be used in transmissions which
recommend 75W, 80W, or 85W GL-4 gear oils, or SAE
30 or 5W/10W30 motor oils. If a 90W GL-4 or SAE 40,
10W40, or 15W40 is required, MT-90 may be used. If the
transmission or transaxle requires an SAE 90 GL-5 gear
oil, then Red Line 75W90NS or 75W140NS Gear Oil
may be used. In transmissions which recommend Dexron
or Mercon fluids we recommend our D4 ATF which is
very similar to the MTL, being a GL-4 Gear Oil also. The
D4 ATF will provide better low-temperature shiftability,
and the MTL would provide better wear protection for
racing use. MTL is not designed for use in rear-wheel
drive differentials. Those generally require a GL-5 lubricant
such as Red Line 75W90 Gear Oil. It is not necessary
to flush the transmission before replacing with MTL.
Remove the drain plug and drain while warm. Seal
compatibility has been designed to be similar to petroleum
lubricants, and leakage should be no greater than
any other oil of comparable viscosity. Being formulated
with extremely stable synthetic basestocks, MTL and
MT-90 will last much longer than conventional petroleum
lubricants. However, we do not recommend extended
drain intervals, since without a filtration system, there is
no way to remove metal shavings other than draining the
lubricant. The regular maintenance intervals are also
recommended to insure that the proper level of the fluid
is maintained."

I have found before that they specifically prohibited use with hypoid gears, but I do not see that here in such plain speak. OUr boxes need GL-5, but they do not have brass or bronze synchros so the wear there is not of concern. We do have such yellow metals with in the gear box, though, and the GL-5 stuff can attack and oxidize the metals so that they are not pretty...but after 30+ years this has not become a failure point or even a perceived failure point.