Depending on the trim level and body style, 5AT G35 can have VLSD or the open diff. 6MT G35's only have the VLSD IIRC because they had the sport packages. The Z 5AT's come in trim levels with only VLSD. The only Z with the open diff is the 6MT base model. The VLSD's for 5AT (3.357) and 6MT (3.538) are 2 different part numbers. Lots of only's in there and only one or....

My 2005 5AT G35 had the VLSD because I had the sport tuned suspension package, otherwise it would've had the open diff.

Regardless if you have an open diff or VLSD, if you go from 3.357 to 3.692 or 3.917 with a rebuild of the internals, you must find a replacement differential. End of story.

 

how much do these replacement differentials go for?

 

Aftermarket diffs range in the 800-1400 range. If you have to replace your diff, do yourself a favor and get something better than an OE VLSD to replace it with. It'll do you much better in the long run.