Step 1: Change the oil.

Our manuals are dated and have (now) "special" fluid requirements that present-day transmissions do not. Don't use 75w90 or 80w90 off of the shelf, and don't use motor oil. You need to find a fluid specifically branded for synchronized manual transmissions. Why? A lot of modern light duty transmissions have actually been designed to run on motor oils like 5w30 and 10w30. This doesn't include the AX-15. Some people will say it's okay based on a couple of months of use and cite an official Chrysler announcement that they were no longer stocking the correct fluid for an out-of-warranty third-party transmission... (Aisin-Warner AX-15 is basically Toyota) Other, often heavy-duty, synchronized transmissions make use of hard metal synchronizer rings that last a long time and can take advantage of the high levels of anti-scuffing additives in ALI GL-5 hypoid gear oil and MT-1 transmission fluids. However The AX-15 has brass synchronizer rings to which these additives are corrosive.

Most high-mileage (abused) gear boxes will probably be happier on a heavier oil like Redline MT-90. If you live somewhere cold Redline MTL or Royal Purple Synchromax is a decent choice. Pennzoil Synchromesh (75w90 base stocks) and AC Delco Synchromesh (lighter than 75w90, can't remember, but damn expensive) are also options. If you can find a gear oil that either isn't API GL-5 rated *or* achieves a GL-5 rating *WITHOUT* the use of sulphurous EP additives you're good to go.

Like others here I run the Redline MT-90 fluid and am very happy with it. Local NAPA suddenly started carrying it one day