91_5.7_TPI

iTrader: (2)

I've noticed alot of people on the site run 3.73s instead of 4.10s when running TBI or TPI and a T56. Why is that? I know that most LT1/LS1 guys prefer the 4.10s. Wouldn't 4.10s be 'better'? Does it have something to do with the power band topping out at or below 5500 and not 6000+ like the LT1/LS1??
I'm asking because I plan to install a T56 soon with my mostly stock L03 and wanted to make sure I got the right gearing.

Darkshot

iTrader: (4)

LT1 and LS1 cars do better spinning faster so they soak up those 4.10 gears like its no thing and still get good mileage because you have a 6th gear with the T56. TBI and TPI cars have the torque but dont like to spin as high so you can better take advantage of this by gearing the car so your RPMs are in the heart of the torque curve most of the time. The T56 does make it a bit easier to have a higher gear ratio (like 4.10) because of the 6th gear, but through 1-2-3 (where it really counts) that stock L03 would be running out of breath pretty quick and you wouldn't be going very far very fast.

With an L03 I might even consider a 3.42 gear depending on what you are going to do with it.

Comp788

Darkshot hit the nail on the head on that one. Well put!

91_5.7_TPI

iTrader: (2)

I would go with a 3.42, but wouldn't that make 6th useless at less than 75-80? I mean, with the 3.42s it would turn like 1600 at 70... will the L03 have the power to make it on anything but flat ground at low RPM?

84z28350

Yea, darkshot hit it. You would have to be shifting pretty fast through the first couple gears because they (TPI especially) falls flat on its face in the upper RPMs. By using a higher gear in the rear you allow for more time to eat up that gear while your little anemic motor is still in its powerband!

9157tpi - It probably wouldnt make enough power @ 1600RPM to keep it rolling on level ground @ 70. If it did it would probably be a real pig on gas...

91_5.7_TPI

iTrader: (2)

Yea, I hate having an anemic motor... Can't even make good use of a transmission. If I'd have spent the $5500 I put in the car elsewhere, it might not be so slow.
Would swapping a T56 into my car be advisable? And if so, with what gear?