Are there conservative dialects of french in which the phenomenon of liaison is not present,so that consonants at the end of words are always fully pronounced?
If you do not have a liaison, on the contrary you do not pronounce the consonant at the end ;
liaison : un grant arbre (un grand arbre)
no liaison : un gran arbre (un grand arbre)
There aren't, properly speaking, dialects of French, merely regional particularities which are never too far removed from main stream French. What you find, though, is a number of completely different "languages" ; they are limited to regions too, are not always full fledged languages (no written form) ; some of them are call "patois" in French ("patois du Midi" for instance) ; others are ancient languages such as Provençal (written form) ; it is not known for some of them, such as Corsican, whether they should be called "patois" or "langue" (not all people agree on that point). Therefore there does not exist a dialect with such caracteristics as you mention ; however, French people in the lower classes and those with less education use less liaisons than the rest of the population.
Moreover, the art of liaisons is a conservative caracteristic of the language.