So been driving for 5 days with the valvoline synchro. The shifting is perfect. Not one crunch or hard to get into any gear. The downside is the trans is noisier and feels looser, probably because my 833 needs a rebuild. But it just shifts perfect after changing to synchromesh. I might drain a quart, and add a quart of 75w140 , to see if it will "tighten" up the trans about without causing a shift problem. Trial and error, money, and time. Anybody have any experience with blending synchro with gear oil?