I have been reading about changing out the differential and about the multiple option. My question is which gear ratio and what effect will the change have on my car. I am leaning towards the 3.42's for my 03 with an A4. With this change I am wanting to get better acceleration to the point I can burn a little rubber at stop signs/lights. With my 3.15 gears I am not able to do this currently.

I have read good and bad about making this change and also about adding a TC. Retain the driveability and handling on the street is important. Any information anyone can provide to make this decission easier would be appreciated. I am doing an exhaust and Header upgrade in three weeks so if I am going to upgrade the differential this would be the time.

 

here's mine with 3.42's and a girl behind the wheel:
http://hometheater.home.att.net/ohiogirl1year.mpg

most will probably say that going from the 3.15 to 3.42 is nto much of a change... and it's not. There is a noticeable improvement, but it is not day/night.

In my case the 3.15 to 3.42 put me exactly where I wanted to be; but each persons wants/goals are different.

 

I have 3.42 gears and a mild converter (see signature). Driveability is like stock and performance improvement is awesome. This is the best performance mod for the money on A4 cars. Most of the Forum will tell you to get taller gears (3.73) and a higher stall converter (3000 RPM and above), but I am very happy with my set up for street/strip. Make sure you also get a trans cooler.

 

Well, it would depend on your budget really. If you want to spin the tires, and keep your stock 3.15s than just get a new converter. You will spin with no problem at all....

 

I went from 3.15 to 3.42 gears on my '04 A4 (with stock TC) and was initially a little disappointed. As mentioned earlier it does make a difference but the change is not night and day. For city driving the 3.73 gears might be a better choice. For highway driving the 3.42 are just right for me (3.73 might raise the RPM enough where it could get annoying at 75 mph).

I'm personally very happy that I have stayed with my stock TC. Drivability is perfect. I've read mixed reviews of various higher stall TCs and the one that I got a ride in seemed a bit loose. You really need to drive in a car with the TC that you want to see how it suits you.

For day-to-day driving gears will probably be your best bet. For the best quarter mile improvement a higher stall TC might be the best bet.

Another thing to consider is that with the 3.42 gears you can get Z06 gears (shot peened) and even have them cryogenically hardened (DTE does this with their gear sets) so it might be a little more durable than aftermarket 3.73 gears, even if they are cryogenically hardened.

BTW, I can spin my tires with ease at most speeds (even with Z06 rims and F1 SC tires) but I think that is more attributable to my engine mods than gearing.

 

So what about the switch from 2.73 to 3.42's ? I've read this is a good mod for low end power...was not planning to change the TC and my heads and cam are stock.

Is this a good move?

 

This is a good move. The sotp difference is immediatley felt. Throw in a TC and roast your tires to the rims at your whim!

 

I was going to do the swap until I decided to sell my '99 A4. The only difference was that I was leaving in the stock converter.

 

Last month I took My car to DTE they took out my lame 2.73s and put in 3.73 with vig 3200 tc and dyno tune. WOW at 20mph it will smoke the Goodrich TA's When it shifts to 2nd more of the same the car is so much more fun to drive now I could not even squak the tires from a stop before Now from a dead stop smoke and sideways. Was not cheap but worth every penny You will not be sorry just do it

 

I changed my 99 A4 2.73 rear gears to the 3.42's last year. I couldn't believe the difference in the car, before it felt sluggish from a start and didn't feel fast until the top of first gear. Since the change it spins the tires very easily. I had to get a programer to reset the computer for the new ratio which also removed torque management. So now I am wondering how much of the improvement was the gear change and how much was getting rid of TM. If I had to do it over again I would have done the programmer first to see what it was like before i changed the rear. I would have needed the programer if I did the 3.42's anyway. Just something for you to thank about. By btw I used a Predator programer.

 

Go back a few years and everybody was saying 3.73 was too much gear. Of course, there was only one vendor and it was like $2600.

rjung, pester C5XTASY about his recent mods. He had similar goals in the he didn't want to stray too far from stock-type reliability and drivability. His observations might give you some food for thought. The gear change is a great plan, be more cautious about a converter. It's important to pick one with the right characteristics for your goals.

 

Thanks for all the input.

I plan to have A&A Corvette here in SoCal do the work and their suggestion was to leave in the stock TC so I'll likely go with that advise. Figure I might was well get the Dyno Tune while I am there....boy, I hope this works out!

 

Kurt, how're you doing? Got the Yank SS3200 installed and the car is fantastic! This is a tight converter and at light throttle is near stock-like. The car creeps at idle, holds on steep hills, and drives great. of course. remember that my idle is up around 775-800 rpm. Say, thought I'd throw this info into this thread as it's pretty interesting.

Individual overall ratio of an automatic A4 C5 in each gear:
2.73 - 3.15 - 3.42 - 3.73
8.35 - 9.63 -10.4 -11.4 (1st gear A4)
4.42 - 5.10 - 5.54 - 6.04 (2nd gear A4)
2.73 - 3.15 - 3.42 - 3.73 (3rd gear A4)
1.91 - 2.20 - 2.39 - 2.61 (4th gear A4)

BTW, I decided to stay with the 3.15s, as my current WOT 2-3 shift now occurs at about 100 mph. This makes for a tremendous freeway passing (playing ) gear. Also, this keeps me in the non-resonance band of my GHLs at freeway speeds, which was very important to me.
rjung, if you want to talk about what I did, power-wise, what my design goals were, and, where I ended up, let me know and I'll fill you in. I'm very happy!
Ed

 

There isn't enough of a difference going from 3.15s to 3.42 gears. If I were you I would install a Yank SS3200 instead of just 3.42 gears. Or the SS3200 with 3.42 gears.

 

not to be an a$$ or anything, but i would think spinning the tires on a C5 even with 2.73 gears should be NO PROBLEM - is your traction control on?

 

I have an 04 A4 with 2.73 gears and can spin the tire with no problem. Now I will say I would love to change to 3.42 since the 2.73's really suck but no money for it today. It will be my next mod.

 

Thanks everyone for the info. I am as unsure as ever. Currently it is a toss up on keeping the 3.15's and get a TC, change to the 3.42's, change to the 3.42's plus TC, or go to 3.73's. This change is not cheap so I want to do the best thing. Changing from 3.42's to 3.73's is no additional cost if I do it intially and if I need a TC I can afford to add that also. My fear with the TC is making the car loose which over the last few weeks I have read about in other threads.

All of you guy's are great thanks for the help keep the info coming. I am unfortunatily at a disadvantage because in my area I do not have any contacts to ride in a car with any of these changes.

 

Based on what you've said so far, I'm inclined to think stick with your gears and opt for a converter along the lines of the SS3200.

 

I did the gears first ..... 3.15 to 3.42 and liked it alot

Later I did the TC (Vig 2400) and now it is terrific.

Knowing what I know now....... I would do the TC if I could only do one. But you should do both if you can afford it. Otherwise later you will pay for labor again....like me


DH