1) Chug along 2) Do a monotonous job 3) Drudge 4) Drudge or trudge 5) Footslog 6) Galumph 7) Get through dull work 8) Go laboriously 9) Graft 10) Grind 11) Groove without mace 12) Heavy tread 13) Labour 14) Lumber 15) Lumber along with heavy steps 16) Make gains the hard way 17) Make heavy work of 18) Make slow progress 1) Footslog 2) Lumber 3) Slog 4) Squish 5) Tramp 6) Trample 7) Trudge 
• (v. i.) To travel slowly but steadily; to trudge. • (v. i.) To toil; to drudge; especially, to study laboriously and patiently. • (v. t.) To walk on slowly or heavily.
Plod intransitive verb [ imperfect & past participle Plodded ; present participle & verbal noun Plodding .] [ Gf. Gael. plod a clod, a pool; also, to strike or pelt with a clod or clods.] 1. To travel slowly but steadily; t...Plod transitive verb To walk on slowly or heavily. « The ploughman homeward plods his weary way.» Gray. 
continue doing something without resting 
Plod is British slang for a uniformed policeman.
noun the act of walking with a slow heavy gait; `I could recognize his plod anywhere`