I think gu5 is 3.23 but am not 100% syre, i also thought the a4 had 3.42 and the m6 had 3.23. now i dont want to kill my gas mileage with 3.73 gears, if i get 3.42 over the 3.23 about how many tenths will that shave off, and about how man less mpg will i get with 3.42 gears? how bad is the gas mileage with 3.73 actually? sorry for being a pain please bare with me

 

6 speeds are 3.42's and auto's are either 2.73's or 3.23's

 

Most A4s came with 3.23s, and in reference to your other thread, this means you have an aluminum drive shaft.

I don't know how much 3.73s would affect times and gas mileage.

 

GU5 is the rpo code for 3.23 gears. The 3.23 gears are the "performance" option for a car with an automatic transmission. Before you worry about changing gears you should consider buying an aftermarket stall convertor. A convertor in the 3200 to 3500 stall range will take about a full half second off your quarter mile times.

 

Forgive me if wrong, but should't the convert be the last mod b/c they tailer make the convert to what is in the car. If you get convert 1st and then change gears,shift kit,recal the computer ect...,wouldn't the convert be less effective?

 

Actually the convertor gives you the greatest gain of any single mod and should be the first mod. A stock A4 car with a decent convertor will eat M6 cars for lunch. As you add hp to the motor the same convertor will stall slightly higher. If the time comes that you want to restall, most convertor companies offer at least one free restall.

 

Sorry,I don't know about install on the convert.I would prefer to do this only once,am I being to timid on this?

 

Labor for a convertor install should run between $150 and $200. That's why people should get a decent sized convertor the first time instead of wishing they had bought a high stall unit after just a few months. You usually can't go wrong with a 3200 to 3500 stall convertor. I just changed from a 4200 TCS to a 3200 Vigilante. The 4200 was too much convertor for a healthy shot of nitrous. The 3200 will cost me about a tenth NA but should actually be several tenths faster on the nitrous.

 

I can't really answer your question about the gas milage on gearing the A4 tranny, but I can tell you what changed when I put 4.11 in my M6 ...

City MPG stayed about the same at 17 MPG. But, Highway MPG dropped to about 19.