I'm getting ready to buy the 4.56 gears. But can I buy the Comptech
differential later on or do they both need to be swapped at once?

And is the $125 parts req'd for the install?

 

No you don't need to buy the comptech differential but it's better to get it when you get gears so that you'll save money/time by installing both at once. Unless you like to keep your S in the shop all the time instead of enjoying it. Get the gear and differential together and get both installed, that way when it's done it's completely done.

 

You can install the gears into your existing diff now, but my advice is to get the Comtech now and install the gears into that diff, otherwise you'll have to remove your existing diff later, remove the gears and install the gears into the Comp diff then reinstall. A big waste of time and money!