96 Rear Axle Ratio Change

[Skyguy007]

I have a '96 Grand Sport that I think has the stock 3.45 rear gears. The problem with this ratio is that I can't really use 6th gear (.49 overdrive) much below 80 mph, which equates to 2000 rpm, without lugging the engine.

I'm looking for members' experiences and suggestions on a source for something more like 4.11. This would give even scarier performance off the line and allow me to use 6th gear for more highway-legal cruising. After all, I'm not going to check out the '96 road test top speed of 164.

 

[Ken]

^^^

 

[vader86]

Just about everyone who has gone from 3.45 to 4.10 has raved about them.

 

[SkunkCar]

The problem with this ratio is that I can't really use 6th gear (.49 overdrive) much below 80 mph, which equates to 2000 rpm, without lugging the engine.

Your motor will pull strongly, without any issues, well below 2000 rpm with the 3.45 gears. As a general guideline, Gordon Killbrew suggests that we not run in 6th gear below 65mph. I follow this guideline in my daily driving both in my Grand Sport and in my '89 6-speed coupe, and it works great -- no problems.

 

[FX GS]

How do 4.10"s affect top end?
What about 3.73's?

 

[Skyguy007]

With the 3.45 ratio, the mildly tuned LT4 in my GS turns 2000 rpm at 80 mph. Using the tools in the Action Center Tech page, I've computed that it will turn 2378 at 80 mph with a 4.10 gear set. The 2000 rpm speed drops from 80 mph to about 67, which would mean that I'd get to use 6th gear a lot more for cruising at a near-the-speed-limit range.

I'm not sure about your Vette, but with mine the constraint is HP versus air resistance. With the 3.45, 80 mph at 2000 rpm equates to 4000 rpm at 160 mph, etc. The car's been road tested to about 165 (in both 5th and 6th gears), which tells me that engine power output, not rpm, is the limiting factor.

I've been told that the gear switch performed by a reputable shop (for warranty purposes) will cost about $2,200 - so it wil be a while before I consider a ratio change. I also discovered that the Dana Super 44 rear end is also used for a Viper. I've been told that Vipers with 4.10 gears are tough to get to stop burning the tires off the line, so I don't think that ratio is very popular with Viper drivers.

 

[Rich96c4ce]

Just get some real tires, like 315 Nitto Street D/Rs, and lay off the loud pedal a little. And anyway, who cares about Vipers, as long as we can use their ring and pinion.