Hi all. I have a HJ van with 308 and TH400 with a 3.08 diff. The van is my daily and I am considering acquiring a Gearvendors overdrive unit https://gearvendors.com/index.html/ so I can drop the diff ratio to3.9 for a bit of poke off the line whilst still retaining highway manners. Does anyoneknow if the tunnel has to be clearanced for such a modification. I saw a video of an install into a Corvette where some bracketry had to be trimmed. Any tips or advice would also be appreciated.
Cheers