I am needing help selecting a proper gear for my uncle's 94 A4 Z28. He wants to retain decent gas milage but wants better acceleration. So he has 3 choices, 3.23, 3.42, 3.73. I have drove a few LS1 cars with 3.23s and I liked them alot. The cars aren't screaming going down the road but have good acceleration. One of my friends switched from the 3.23 to a 3.73 and did not like it and he went back to the 3.23s, again an LS1 car. I do not know how LT1s compare though. So here is where your advice comes into play. The car currently has a 2.73 gear along with an off road y pipe with a flowmaster y and a LS1 flowmaster american thunder catback. The only other mods it may get are headers and a cold air intake. So with this in mind, what would be the best gear for him? I am currently leaning towards the 3.23.

 

I drove with a car that had 3.42's, and they are nice. He said he still gets 18-20 mpg on the highway, and the acceleration was awesome. Not overkill, yet just enough.

 

Getting 18-20 mpg with 3.42s in an auto is not very good at all IMO. I know this is apples to oranges, but I have the same gears in my car and I got 29.6mpg on the way down to Iowa last summer. My car has H/C/E and around 450FWHP. Heck I get 18-20 city while driving up here in St. Cloud. I would think an A4 with 3.42s should get mid 20s on the highway.

 

If he wants better accel + the best gas mileage 3.42's are probably his best option - but 3.73's aren't that much different. With my stall and 3.42's I average 24.2 on the highway/15.8 city. His driving habits may vary.

 

I have a LT1 383 and I was getting about 17 combined highway/city with a stock 2.73 gear and switched to a richmond 3.73 set and saw virtually the same mileage. I tuned it for open loop fulltime and managed to squeeze it up to almost 17.5. I never saw better than 19 with all highway driving. I had a 2600 stall TC with both setups. The restalled TC probably hurt mileage more than the gear change.

 

My friend has been very happy with the 3.42's in his '96 T/A A4. Mileage and performance (although his track #'s aren't great, but he wasn't hooking up ).

I've had 2.73's, 3.73's, and 4.10's in my car! Honestly, never saw a HUGE mileage drop ... yes, a little, but not a lot. I've never had 3.23's or 3.42's, but from everything I've READ, and my buddy's experience, 3.42's are a great "compromise" . All I know is I still see a bunch of the 3.23 crowd talking about switching up to 3.73's.

 

Mid 20's on highway with an auto?! You're a 6 speed, so thats why you got such good milage with 3.42's. They came stock with 6 speeds. Autos with 2.73's (which I have) do not even get mid 20's. I get 24 TOPS, without any fun driving at all. So 20 or so mpg with 3.42 is pretty reasonable. Yeah it could be better, but not by much. My window sticker says 17/24 for milage. That is roughly what I get.

Also, where in st.cloud are you? Are you near the uni?

 

Thanks for the replies. I'll give him this info tomorrow. I think he'll end up going with the 3.42s. He purchased a 1978 Z/28 new and still has it, and it has the 3.42s in it as well.

 

3.73's

 

My old 94Z with an auto got around 24mpg on average. I belive that had 3.23s. I'm not sure that was back in 99. But I know I averaged mid 20s. I don't think I ever saw anything less then 20s.

I'm about 3 miles from State. I closer to Hwy 10 and Hwy 23 intersection.