What kind of gain should I see in the 1/4 going from a 2.73 gear to 3.73 say in a pretty much stock L03 3rd gen?

Hard to say; prolly not much.

Reason being, it will force the engine RPM up into a range where the engine makes absolutely no power whatsoever.

It'll 60' ruthlessly, if it hooks up; but that's about it.

If you've ever rode in or drove one of those cars that takes off from a light like shot out of a cannon, but can't pass a semi on a 2-lane road at 50 mph, then you have a pretty fair idea of what you'll get.

Now... uncork all the L03 problems (crappy exhaust, every single piece), crappy heads, and crappy cam, ... it becomes a WHOLE OTHER matter.

Im not really trying to get any power out of the L03. Ive already switched to 3in exhaust, got a beefed up 700r4 with shift kit and that's about all im gona do to the car until I get my 350 built. I will not waste the effort in headers or anything to really enhance this tiny smallblock because ive been that route before.But I am going to go ahead and swap my worn differential and go ahead and go to 3.73 gears while I was at it. Im slowly getting my parts together and the rest of the car ready for the better engine when I decide to do the swap.But I was just curious with the 2.73s its very lazy I have wondered how much the 3.73s will wake up the high HP L03..Lol And Sofa you are spot on with that description, as it sits now it takes off like a rocket and runs out of power at 70mph.

I went from a 2.73 to 3.42 and Eaton Posi. and there was a dramatic difference.
You might want to think about the 3.42 ratio. The 700r4 has a decent first gear stretch with that ratio but the 3.73 is going through it fairly quickly.


Even my little 5.0 pushes me back in the seat with the seat belts locking and a nice loud BARK of the tires hitting second. I can even chirp them on the second to third shift and that's all done with only a Corvette servo..
So what type of L.S.D. are you going to run.

Im getting an Auburn w/3.73 gears its coming out of a wrecked 84 H.O 5spd car with very low mileage 30-40k I think. Really cheap, or else I would have went with an Eaton or some of the better differentials and 3.42s. I would rather have 3.42s.

Installing a used Auburn? I see you enjoy one tire fire, lol. Do it once & do it right, don't put an Auburn in it.

I know the car its coming out of and it has been pampered to say the least so im going to take a chance on it especially for the price im getn it for. I know Auburn is not the best but I have put some bad punishment to them over the years and most have held up pretty good. Im pretty easy on my car I wont be drag racing it any time soon just wanting a lil more pep out of it.

The test that were made on this went from a 2.73 to a 3.73 with a mostly stock 350ci. motor and dropped an average of 2 tenths in the quarter mile. With the 2.73's and a 9.5" lockup torque converter with apx. 2,800 - 3,000 rpm stall it dropped 5 to 7 tenths in the quarter mile. They ran drag radials to see the actual gains with no tire slip. I have seen similar results in other torque converter and rear end gear change comparisons. Gears make very little difference in the quarter mile in the vast majority of cases. On the street the gear ratio change feels like it does much more than what you see here. Torque converters do much more than a gear change in the quarter mile as you can see here. If you do a lot of freeway driving the 2.73's do keep the rpm's down and give better gas mileage. The right torque converter would be the way to go and get the performance you want without sacrificing the gas mileage. If you want every little bit that can be gained in the quarter mile, then the torque converter and a gear change would be in order.