Thanks! Glad to help.

I made that one up quick for the A4.

I have a better one for the M6, because it's what I drive.

Dan

 

Now what is the difference in shift points w/ an M6? Dont 3.73 come stock with a M6 Z?

 

M6's come with 3.42's in the rear. The manual tranny gear ratios are also different, causing different shift points. I don't have that file loaded up on the internet yet, so I can't link to it. I'll do it soon though, and probably post a seperate post.

Dan

 

How much of a change in gas mileage will there be with 2.73s to 3.73s? My T/A is a daily driver and I don't feel like dishing out a bunch of $ for this mod. Nice spreadsheet BTW.

 

It all depends on how heavy your foot gets. With the added fun of acceleration I'd bet you'll suffer a little gas mileage decrease. I've heard if you drive conservative it isn't bad at all. Because the car doesn't have to work as hard to get off the line you actually don't suffer much at all if you don't do too much highway driving.

 

How many rpm's do you pull with 3.73's A4 on the freeway at 75mp?

 

mine are FINALLY in. but theyre on the stock tune so my speedo reads wrong. basically im going 3/4ths of how fast my speedo reads.

2,000rpm with 2.73s = 80 mph
2,000rpm with 3.73s ~ 60 mph

3,000rpm with 3.73s is roughly 80 mph, maybe a little more. I cant really tell till I get my pcm redone.

and yes the car pulls better in every gear. it seems to lose its high end but thats not the case, it just accelerates much much faster from a standstill so it only seems like you lost it.
Now when I stomp on the gas the car absolutely rockets forward. Drop the car into 1st gear going about 20 mph and the tires break loose and you get catapaulted ahead.
Its a great feeling feels like I added 50 hp.

 

I doubt there is that big of a difference when switching from 2.73 to 3.73. I would bet there is only a small difference.... instead of 2000 rpm at 75, it'd be 2400 or so. No hard facts, just my opinion.

 

sorry bro, but youre wrong, theres a big difference. i only switched to 3.42s and im at 2425 ish at 75 mph. and the car deffinently pulls harder in every gear at all speeds.

 

I'm not saying you are lying or anything, I just find it hard to believe. Although, you would know more about it since you actually did change gears. I guess I gotta see it myself.

 

Here's my thoughts on 2.73 to 3.73's.....

3.73's are good from a stop and from a rolls, except for anything over 60mph and below about 75. 2nd gear at 70mph with 2.73's rocks compared to low 3rd of 3.73's. Also think about what you plan on trapping, because you don't want to trap over 3rd with 3.73's.

Gas mileage won't change that much, maybe 2mpg, which really isn't that bad. Assume you drive 500 miles a week(which most don't) by 52 weeks a yr. Thats 26,000 miles/yr. If you get 22mpg before and 20mpg after it'll cost you an extra $213 a year for the better gears(assuming $1.80/gal). Now for an about 58 cents a day, wouldn't you rather have better gears?

 

I switched from 2.73s to 3.73.

Huge difference at all speeds with the 3.73s. Much better low and midrange. The topend is not reduced either... unless you can pull 4th to redline with the 2.73s (fat chance for most)

As far as running out of gear in 3rd in the quarter with 3.73s - well, odds are you're not going to trap high enough with the stock cam to have a problem. Larger cam will allow higher rpms and more trap speed.

With the 3.73, the a4, and 26" tire, I ran approx 2600rpms at 80 and 3000 at 100mph. Normal highway driving I got 20mpg

IMO it's the perfect all around gear for an auto. It defintely helped reduce the flat/mushy areas you feel with the 2.73s or even the 3.42s (which I ran for a while also)

 

Not exactly true. With 2 identical M6 cars, one with stock 3:42's and the other with 4:10's from a standstill the 4:10 car will accelerate faster than the 3:42 car. But say from a 70+MPH roll, the 3:42 geared car will out accelerate the 4:10 car.

 

Same applies for the A4 I assume, so you gain low speed acceleration for some loss of high speed acceleration.

-Dustin-

 

It ends up being a pretty big gain at the beginning of 1st gear, IF YOU GET TRACTION. After that, it's pretty much a wash, with the 3.73's being slightly slower. This is assuming a WOT run.

The TQ is higher throughout the RPM range in each gear, but you run out of gear at a lower speed in each gear, that's the problem.

Dan