Hey Guys...I am considering installing an R180 diff with 4.11s (non LSD) in my stock '72 (original 2.4 engine with no mods). I will also be installing a 5-speed with a .8 overdrive. The original 3.36 rear is still in it. I ran the numbers and with the .8 rear, and the final drive ratio will be about 3.29. I plan to leave the engine alone and am hoping the 4.11s will wake the Z up a little at stoplights. How streetable is this combination?

Tire size is the other variable. Use the calculator to see what different combos are like:

http://webspace.webring.com/people/cz/z_design_studio/

It's all a gain

I installed a 4.11 R180 out of an early 80s truck into my 72 240 and it bolted right in. I have a 5-speed transmission and 205/60/R14 tires. My speedo cog isn't correct so i'm not sure of the exact speed, but I think it turns around 3500rpm at 70mph. Gas mileage may be a concern if it's a daily driver, but the overall drivability seems just fine to me. Acceleration is definitely improved IMO.

Go for it!

I have a '71 which I installed a 4.44 large case and 5 speed (.85 5th) back in '72. I liked it, didn't seem to affect gas mileage that much. In fact on a drive from Oregon to Florida in '75 I got 30 mpg on a long stretch of west Texas.

Yup, fuel consumption won't change much given the same style of driving. People probably tend to drive the cars harder with the lower gears, giving the perception that fuel mileage has drastically changed.