You mis under stood me

the VS abrams and leopard tanks where like there first tanks out they had a clicker clutch in the gear box and now the latest versions of them remain the same but with new style electronics and radios..other than that the whole tanks are the same as old first release versions.

Now the rest of VS tanks releasted after diferent tanks like KT and tiger one and t72 and so on use a totally new clutch system only abrams and leos have old clutch style.

try doing the break in like i stated above it may work.

also it could be the electronics making one motor get more electric than the other/

if you go slow speed farward does it go straight?
second speed?
third speed?
or on all speeds it goes crooked?

farward and then backward is it the same side track turning slower making it go crooked in the same farward and backward directions?

If so maybe you have a pair of very unmatched motors one having much more RPM than the other.

Also try this put the whole track from one side of the tank on the oposit side another words swap em from one side to the other this may fix the problem.