yes that about right a lower T motor will mostly give you more speed and less torque as a say 35t 45t and so on will be slower with a lot more torque for crawling..but are you sure there is no issues with the pumking as you say it ran ok before and has just stopped it may be worth stripping it down and checking all the gears etc in case you have shredded any gears or any thinbg that could be wrong with it..