Vehicle: '83 F350, 460, C6, 4.10, 10,000#GVRW, 75,000 actual miles (sat unused for ~5 yrs before I bought it).
Problems: 1. Slight "shudder" in 1st gear when starting off and in 2nd at about 25mph. More pronounced when cold. 2. Front transmission seal is leaking enough to stain driveway. Transmission fluid is brown (but doesn't smell burned) and likely has never been changed. I plan to replace fluid and filter. Questions: 1. Mechanic neighbor recommends Lube Guard (red) additive for "shudder"; any recommendations? 2. Is there an additive to "rejuvinate" leaking seals that really works-what is it? 3. What brand/type of fluid would be best for this transmission.