We did the Trans Labrador highway back in 1993 a few years after the road opened. At that time most of it was "pit run gravel" meaning large boulders etc., I suspect that it is better now.
We started in Baie-Comeau Quebec and went up to Lab City, that section was generally paved and in good shape. We didn't do a lot of research and had wanted to stop in Gagnon, about halfway between BC and Lab city, but found that it was a ghost town vacated by the industry previously there.
The section between Lab City and Goose Bay was fun, we pulled over a couple of nights in undeveloped gravel pits along the sides of the road.
We had no problems with our 5th wheel RV, but we took it easy. The only problem was getting a fill of winter grade diesel in our pick up in GB in July, it's like vapour lock in a gas engine, that fill eventually caused the failure of the starter (too much cranking).
We then took the car ferry (with our RV and truck) down the coast and landed on the island, a good trip. The car ferry was big enough that it had railroad tracks to handle rail cars!