Today was my first day driving on my new 3.73 rear. I noticed my car was running substantially leaner across the board. Is this normal..or is there soething wierd going on?

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I expected someone else would have responded by now, but since no one has, I'll put in a couple of pennies.

With the higher ratio, your engine will not "work" as hard, so your vacuum should be higher. This typically translates to a leaner command. I wouldn't think that is a problem by itself, as long as it seems to be running okay otherwise.

I just went the other way for now, replacing 3.08's (howled, basically worn out by neglect of former owner) to 2.73's (from donor car - quiet, smooth). The engine has to pull harder to do the same work at comparable speeds. I don't have mixture info, but I would guess that it is richer since the engine is loaded more. But, since the RPM's are down, I'd expect better overall mileage.

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82 Berlinetta, orig V-6 car. Rescued w/86 LG4/TH700R with all harnesses, sensors, ECM, etc. 2.73 open, cat-back from '91 GTA, Accel HEI SuperCoil. AMSOIL syn lubes bumper-to-bumper. Daily driver, work-in-progress (LB9 w/ZZ3 cam, ported heads, exhaust, paint, etc.).
57 Bel Air, my 1st car. Currently 396 .030 over, Weiand Action+, Edelbrock 1901 Q-Jet, Jacobs Omnipack, 1-3/4" headers, TH400 w/TCI Sat Night Special conv & shift kit, 3.08 10-bolt, AMSOIL syn lubes bumper-to-bumper. Best 15.1 @ 5800' Bandimere. Daily driver while Camaro was being put together.

 

yeah...I was kinda thinking that.but it was a big drop. I wouldn;t have expected that much..it went from the 8-9th bar on my a/f gauge to the 3-4th.

On the good side...my cruise mixture is perfect now..was always too rich before