wk caprice speedo out (changed diff) south australia

[Jacob1991]

Hi all,
i have a 04 caprice 5.7L auto,
have recently changed my diff from the standard 3.08 to 3.46.
now my speedo is out and wondering if you know anyone in adelaide who can adjust it.
alot of mechanics dont want to know about it or dont have a tech 2 computer,
and i cant justify paying holdens $130 for what ive heard is a 5 min job.

 

[Munz]

somewhere that can tune an LS1 can do it