| So I asked the question on the 4.10 upgrade on our 300ZX. I just picked up my car from having the gears installed. The first time the gears were installed they were simply slapped on and checked to see how bad they sounded. The simple truth was that whined and whined loud in just a few feet the results was noticible. The car was maybe driven 100 ft. This what I considered most do and then complain of the gear whine. So what causes this gear whine? Simply the backlash is suppose to be zero and the factory shims are simply not enough and in this case they had to be custom made. So after a new crush collar and some custom shims and a second installation. A new test was done the results were zero whine. So lets forget about the whine and get to the facts. Everytime you upgrade from the factory wheels to 18s and the most common being 275/35R18 and 285/35R18 you change the final gear ratio. So I did simple checking and used these graphs as a guide. 
This is basically stock. 
This what happens when you just replace the gears and have some 18" with 285/35 tires on. As you can see the net result is that have slightly improved gear ratios versus stock and a little top loss. Basically if you have a slightly raised rev limiter of say an additional 300 rpms you have zero loss. 
This what it would be in my case my rev limiter is set 8000 so I have really nothing to loose. And because of my bumped power band I could use some low end assistance. So what do I think of this mod? I am excited it really woke the car up again in the lower RPM band and I pretty recommend it to anyone who has a larger turbos and larger wheels and tires. Oh and in my case I can hear zero gear whine, a small recommendation was to also use Richmond Gear Oil, and do not drive on the gears if they start to whine from the start as you will wear a groove and be stuck with some gear whine.
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Review of Leader Gears - 
13:16:17 12/24/08
