Well, there is that question of whether or not you have the proper spring. There are many to choose from. Did you have the old one to match up? Any question that the spring is hooked up in the proper places? It goes from the tension arm then to the frame rail or some have a extra nutted bolt it hooks to rather than directly in the frame. If it drove fine w/ the temporary set up you had, it would indicate that the rest is Ok. In theory if it is hooked up properly, the VS pulley sticking is the next likely cause. Try running the pedal through the motions whilst still in neutral first, then with it in gear.

I have a troy bilt lawnmower GTX-2446, We bought it used and I can walk faster then it moves. Is there a way to make it move faster?

Likely worn traction belts /stuck variable speed pulley. Should you choose to go further, be sure to use the OEM belts and if you replace the front belt- do the rear at the same time. MTd would like you to always replace both at once. Know that your brake fully releases as well. If not, you could try walking slower,,,,

I had this same issue on my MTD lawn mower. I replaced the upper drive belt and it started working like a charm. I made a video while I replaced the belt. You can see it here. There is also a lower drive belt that I will be replacing soon. I will add a video to the same channel after I record it. https://youtu.be/G20J6LrHgM8

All these threads I'm looking at always have a lot of "could bes"..... but never is posted any final solutions that fixed the problem.

Unfortunately many op never reply back when the solution is posted , human nature unfortunately , life goes on !

Is it hydrostatic? If so might need new fluid. Mine did if on flat ground mine takes M1 15W50. But I found Amsoil Hyrdrostatic way better on hills. Doesn't break down as fast. When it becomes very thin like water and dirty it has gotten very hot and is no longer going to work properly,