I have the original T- Maxx with the Pro.15 as well. I also have a modified 2.5 Maxx. The original does not seem to have much power for climbing. I suppose I could drop a bell gear or 3 and it would climb about anything. Then it would be too slow on the streets. All in all, it is what it is, and thats not all that bad. The newer one does have a lot more power but also more torque to stress more components. Someitmes bigger is not always better. Might be more fun but is definetly more work.