Both are good tractors, DT466 in the 66, DTI466 in the 86, Fuller Roadranger transmissions. Cab is alot nicer on the 86. Front axle is hydraulic resivour for both transmission lube and hydraulic system. rear axle is splash lubed seperately. Other than that just the normal articulation joint wear issues to look for same as any articulated tractor.
If you use them like the 200 hp tractor they are instead of pulling their guts out like a 300 hp tractor they are troublefree. Have put alot of hours on both and would take the 4386 hands down, just because they are more comfortable, intercooled and a few little bit better features but both are good tractors.