mike13

iTrader: (27)

spec's
1987 Iroc
LS1. T56
112magnacharger 450rwhp/450tq car actually makes a little more horsepower but wanted to be on the conservative side.

With the maggie should I go with the 3.70's? Gears in a T56 maggie car is all new for me. It's a fun street car with a little drag racing.

SMOKNSS

iTrader: (3)

What is the intended purpose?

If it were a fun street car, I would give them a shot. Not too far off from the stock gears that come in a M6 f-body. When my car was six speed I actually got better MPGs in the city with 4.10s than with my factory 3.42s.

mike13

iTrader: (27)

Fun street car.

SMOKNSS

iTrader: (3)

Then I would. You wont be out of gear at the truck (if you plan to go) and it should be more fun to drive with a little more gear in it. I would say give it a go.

Have you looked into 4.10s? With a t56 you could actually run more gear and actually be able to use 6th around town.

mike13

iTrader: (27)

no haven't looked into 4.10's

SMOKNSS

iTrader: (3)

I would check into them. There are various gear calculators and things on the internet that can show you what your various speeds will be like. Just to see what rear gear would put you.

I made 440rwhp on motor and never had a problem with running out of gear at the track with the nitrous. I was on 28" tires but I would have been fine on 26" tires also.

Blackpanther99

iTrader: (8)

I would give it a shot with the 3.70s. Best thing to do is take a look at a gear ratio calculator and see the results.

murphinator

iTrader: (2)

with a superchrger you dont need low gears to get/keep it in its powerband , with a 112 on it its going to pull hard whether it has 3.73's or 2.73's.

but if its ever going to see the track at all consider what rpm it will be in and in which gear when it goes through the traps so you dont have to shift just to make the last 100 feet....

mike13

iTrader: (27)

that's exactly what I'm trying to figure out, if it works for or against the combination. I know on a tubo set up I would run taller gearing.

murphinator

iTrader: (2)

my reason for thinking that way is another platform I own and have modded for years is SC3800 FWD cars that have an Eaton m90 SC ( mp 112 is an upgrade) with just bolt ons a stock geared 2.93 car will kill the tires as soon as you stomp it at any speed below 30. some people upgrade those cars to 329 or 369 gears and its typically accepted when you do lower gears you will lose trap speed - every other platform I have ever been involved in for 30 years messing with cars if you lose trap speed you lost power.

NA LS1 cars which I own 3 of currently ( all bolt on cars) could surely make gains with gears or even more so with a stall as they dont make much power below about 3500 rpm - of course they make power very well above that but it was an adjustment to me when I started driving the ls1 cars compared to the 3800 sc cars- the powerband is just different with an sc , a turbo will make more power in a direct ratio to rpm it seems but an sc makes all the power NOW!!!!

in the grand national/turbo buick world the cars came with 3.42's stock and you see people modding them typically stay committed to that factory gear ratio even on pretty heavily modded cars unless they have gone with substantially taller tires and then will gear lower in effect bringing final drive back close to stock

I also used to own a very well built 455 Pontiac that was a torque monster in the early 90's , the friend I bought it from had no clue about drag racing and smoked at least half track on a 14.1 @117 pass lol , the car had 256 gears and if you hit it it always snapped to life - never any lag feeling

I feel on any of these examples I listed if you gear down substantially you will just spin up past instead of stay in the powerband of that combo but if you can find someone with a more apples to apples opinion - ls1 with mp112 I would look at what they give for advice above all if you can find anybody running a similar combo to yours.

what gear is in the car now ?

mike13

iTrader: (27)

That theory makes sense. The turbo Buick guys run a higher gear to load the car which spools the turbo.