will a 4.1 sierra lsd diff be ok for a road/track day car with 14 wheels and type 9 gearbox.running a 3.62 but 4th and 5th seem to high

I didnt know that there was a 4.1:1 sierra diff! Anyway, probably best to run it through Dave Andrews gearing program (http://hometown.aol.com/sarandrews/GEARING.EXE) to see if what you'll get is what you want.

However, you'll see a massive difference between a 3.62 and a 4.1. You might want to look at a 3.92 (these are easy to find ... 1.8 5-speed, or 2.0 injection cars).

Remember that changing the diff can't make up for deficiencies in the gearbox ratios. In particular, it won't help with the enormous gap in the ratios between 1st and 2nd in all the type 9 boxes. This invariably causes the engine to drop off the boil as you make the shift. The only way to solve that involves gearbox mods, which are rather expensive.

Cheers
Richard

try the quaife gearing program. very easy to use.
find it at www.quaifeamerica.com
look under downloads (gearing program)