GT automatic stock 3.15 or 3.55

[Jimdohc]

Thank you for the detailed response. 230 rpm shouldnt be that much of a differences on mpg. Looks like 3.55 rear end is the way to go.

No worries...

I was bored again this morning.

city 3.15 & 3.55- 16MPG
highway 3.15- 25MPG & 3.55- 23.5MPG
total 100,000miles. 50% highway miles cruising in top gear.

city- 50,000miles/16MPG=3,125gal.
highway- 50,000/25=2,000
5,125x$3= $15,375
or
city- 3,125gal.
highway- 50,000/23.5=2,128
5,253x$3= $15,759

$384 more per 100,000miles @ $3/gal

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[jcovaltine]

No worries...

I was bored again this morning.

city 3.15 & 3.55- 16MPG
highway 3.15- 25MPG & 3.55- 23.5MPG
total 100,000miles. 50% highway miles cruising in top gear.

city- 50,000miles/16MPG=3,125gal.
highway- 50,000/25=2,000
5,125x$3= $15,375
or
city- 3,125gal.
highway- 50,000/23.5=2,128
5,253x$3= $15,759

$384 more per 100,000miles @ $3/gal

Jimdohc

Thanks for the breakdown. I'm hoping the 3.55 will improve the city mpg but I can clearly see that its not going to affect the highway miles that much.

 

[svt93style]

3:55 for sure.

 

[jdotjohnson]

On a whim I stopped by my dealership and decided to have 3.55s added to my auto GT. Good thing I did, car was built a week later haha!

 

[Free Agent]

If I ever get my car I'll share my findings.

 

[Turrizm]

You will LOVE the 3:55 gears on the auto.. I have them on mine and LOVE the gearing! Perfect.

 

[DABKO]

You will LOVE the 3:55 gears on the auto.. I have them on mine and LOVE the gearing! Perfect.

Agree.

 

[xsboost]

Yes, there is a trade off.

What will remain to be seen is if 3.55 or 3.15 cars produce better dragstrip times.

There is a chance, I am unsure as to how much, that 3.55 gears may cause an extra shift during the run, thus you might actually produce a worse ET than a 3.15 car

Very true, most people have no idea about this. Just like 373 vs 331.

 

[ry1980]

Thanks Turrizm for your input on 3.55. Anyone else got them instead of the base auto 3.15 gearing? Please share your experiences with daily drivability and fun factor.

 

[BlueSpirit]

Any other comments? I have 3.15 on my auto
but can't decide either to go with 3.55 or 373

 

[aggieStang]

I got the 315s...only because its for my wife to drive and she doesnt need the extra kick

 

[BlueSpirit]

Anyone with 3.73s on auto.

 

[elfiero]

I got 3.15s for the little woman because it's a DD/GG. Lemme tell ya: that thing is a rocket ship- no matter what gear you get. I will keep my eye on ebay for a 3.73/Torsen unit as soon as guys start driving these cars over their heads;)

 

[15GTBEN]

Save the money for the 3.55 upgrade from the factory and install 4.10's after you take delivery. You're going to get a tuner for more power anyway (right, everybody!?!?), so you can use the tuner to correct your speedo. Or, invest in a big stall converter (Circle-D makes awesome stall converters for the 6R80 trans). Better yet, get the 4.10's and a big stall converter.

I'm sure the 4.10's are fun but at the cost of horrible traction in 1st on street tires and highway mileage. Mike R himself has said that anything more than 3.31's with the 6R80 are negligible. It's the torque converter that holds the 60ft back.

OP, If mainly for daily driving, not plan on making big power and want a little extra kick in the pants get the 3.55's.

 

[Old 5 Oh]

Even with the 3.15s, the car leaves the line like it's been rear-ended. The 12% difference between the 3.15s and the 3.55s is not very great, so do what makes you happy. Mine is optimized for the highway cruising that makes up 90% of my driving. If I were a 1/4-mile guy, I'd be more interested in optimizing for that distance.

No wrong answers here. It's NOT like the old AOD/2.73 cars that had same-day throttle response. Leave the car in Drive and it's pretty relaxed, but in Sport, or selecting your own gears, it's very responsive and scary-fast.

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