Originally posted by Sniffle
Also buy the racing trans for the Lexus and the Challanger,
then swap the racing trans codes to have adjustable gear ratios in game,
looks like you already know to add the extra gear ratios from the lexus.
and as Bounkass pointed out change car, change oil, buy a part in tuning shop, go into practise or speed test then it will work.
I moved my mod-savegame again from the Stick to my PS3 changed the Car and back to the Challanger and it works!

Thanks again!
For me, the racing trans is a must have, so every car in my game has one.
How to add the extra gears wasn't so difficult (a big thank you for all the good Tutorials).
I know, there are also some gear ratios free, so I will try to figure out, how to use them, too.