I recently decided that my factory 3-spd needed at least one new gear. Didn't matter which side, either a higher first gear or an over drive 4th. Well, wanting to stay Nissan I looked for an automatic that would fit. It occured to me that if I put the 4-spd Maxima transmission and higher rear gears, I could have a little bit of both. The Maxima has the same ratios as the Z-3spd, but with a fourth overdrive. The performance in 1-3 should then be the same but with the added boost of the rear end. In fourth with overdrive plus the rear end, I should have about the same top speed and fuel economy. I don't top my speedo on a regular basis anyway so that's not a concern. My question is What do I need to do to put the new gears in? Can I just by a set of gears and put those in my R180 (or R200. I'm not sure which it is. It's the 3.545 ratio but I've heard that called both.)? Or would I be better off to get the whole rear end?