Follow up question to the Rear End FAQ

[Thewilldog]

I've got an automatic 01 Z28. I don't know which gear set it has, 3.23 or 2.73. I'm getting a rear end rebuild this week, it's making an disturbing noise when I'm driving. Since they're going to be in there anyways I was thinking maybe getting a new one. Can someone tell me what the increase in performance and drop in fuel efficiency would be were I to switch to 3.73?

Also, that FAQ should be locked and sticky

[t/as&dds]

You'll love 3.73s in your ride. I made that same jump in my 86 Monte Carlo and what a difference!! Great performance increase, minimal mileage loss. Do it...

[keliente]

I've got an automatic 01 Z28. I don't know which gear set it has, 3.23 or 2.73. I'm getting a rear end rebuild this week, it's making an disturbing noise when I'm driving. Since they're going to be in there anyways I was thinking maybe getting a new one. Can someone tell me what the increase in performance and drop in fuel efficiency would be were I to switch to 3.73?

Also, that FAQ should be locked and sticky

More than likely it has 3.23s. Look at the RPO codes (on the side of the door jamb, or in the glovebox). If you see GU5 that's a 3.23 car and a 3 series carrier. If you see GU2 it is a 2.73 car and a 2 series carrier. Know what it is before you switch gears because the new gears will be carrier specific.

You would probably lose a small bit of gas mileage on the highway because your car will be turning a higher RPM. The performance gain is worth it though, it really wakes the car up. Switching to 3.42s wouldn't really be worth your while if you already have 3.23s. However if you haven't added a new stall yet, you should probably try that first (it's essential for an A4 :) )