lonnyh

Ok, I guess my first question is why GM installs a 2.73 rear differential on the automatic version of the 6.2 liter LS3, and offers a 3:43 rear diff. for the 6 speed manual, is there a limitation that forces them to do this. My second question is has anyone successfully swapped these? The cost is approximately 1500.00 including labor and I would hate to get halfway through it and find out the hard way it cant be done. Naturally I called GM service and they had no clue.
Thanks
PS: I realize the obvious solutioin was to get the 6 sp. manual but I liked the paddle shifter of the Automatic, plus got a good deal on the Automatic Grand Sport, even with the cost of the swap!! lol

Gearhead Jim

I too like the A6.

In the Tech/Perf section, there was a long thread about the advantages/disavantages of going to a shorter rear axle ratio.

In summary, on a 1/4 mile drag where you floor it and hold the pedal down, there is very little difference. I think one guy dropped his ET by about 1/10 second by going from 2.73 to 4.11

But in daily street driving, the car will feel much livlier.

lonnyh

ok thanks, I will take a look.

Vette5.5

You really need to look at total gearing at the rear wheels. A6's have 4.05 1st ratio, so even with 2.76 axle, it's 11.2 wheels. M6's have 2.66 1st, and with 3.42 axle its 9.1 wheels. As you can see, factory A6's are ahead in this area. For comparison to a 60's A3 Vette with 2.50 1st, would be similar launch to that car having a 4.50 axle, but no highway o.d. Maybe careful what you're doing, or could end up with worthless lower tranny gears.

lonnyh

thanks vette5.5, this is the info I was looking for. I'll leave it alone.

speedlink

So if I understand correctly, then the A6 would feel more lively at launch. Is this correct?

haljensen

The higher the numerical ratio the harder the launch. the A6 w/2.73 is the best of all factory offered combos.

lonnyh

wow, this table is awesome. thanks

speedraider

put your money into something else

Polar Jet

Give Chuck COW (Corvettes Of Westchester) a call and talk to him about his 3.42 gear package and his COW booster and A6 tune. He will turn the car into a monster.

FortMorganAl

Unless you plan on turning it into a track car with drag slicks, leave well enough alone. You already have gearing that will light the stock tires. Any more torque will just make more smoke until you get more grip.

Purdue

0Chuck CoW

FloydSummerOf68

Gears and a tune don't turn any car into a monster, but it does make the car a bit quicker and it will feel better.

0Chuck CoW

FloydSummerOf68

Deceptikon

I hae an 05 AT4 w/ stock gearing. Would a swap for 4.10 be advantagous?

0Chuck CoW

You want 3.90s my friend...

3.90s are perfect for the A4 cars for both launching and highway....

I've got the perfect tune for them...

Call me if you're interested.

Chuck CoW

Deceptikon

Cool, thanks. Others have said the 3.90 will be good and not much different from the 4.10. I will look into the cost of the 3.90

SL33PER

Just as an FYI, if you've got an A6 and are looking for a MUCH more reliable and cost effective solution to gears then all you need to do is swap in a differential from a ZO6. It's a direct bolt-on to the 6L80 (although using the Pfadt offset differential mounts make it a little easier to install), it's pretty much indestructible and it's about half the price of an aftermrket unit, especially since there is no core charge to worry about. I've seen them sell for anywhere from $1000 to about $1600. Even at that price you can deduct what you can sell your stock unit for it still makes more sense to do it that way.

In addition to making my car a lot more fun to drive on the street, ive put a few hundred passes on it at the track and it hasn't missed a beat so far in over 2 years!

Speedforhire

In response to your initial question: GM used the 2.73's to beat EPA regs in the auto's, thus dropping the gas guzzler tax on these cars. A 3.43 wouldn't cut the mustard.

IMHO: Get the "Z" diff..........your car will love you!