In Reply to: Transmission Fluid in a Manual Transmission posted by Lisa Ryckman on 08/01/01 at 7:48 PM:
Brake fluid is not a good idea for a transmission of any type.
In a manual transmission, the fluid must be compatable with all components. It must have excellent shear stability, a sulphur phos package for long life and a viscosity improver for high temperatures. Brake fluid is simply a special application hydrulic fluid.
Make sure you check your manual for the requird transmission fluid specification. If GL5 or multipurpose is suggested, a synthetic 75w90 or 80w140 are suitable.
If you ever tow anything in hot climates or summer go for the 80w140.
RE: life span
Some OEM's accept drain intervals of up to 250,000 miles. If you drive hard or tow, I would reduce the drain interval to every 100,000 or so.