I will soon be putting gears in my car. I have a 2001 Z28 auto. I was wondering what the best gear ratio is for a car that is daily driven but is raced on weekends? I have heard that 3.73's are good for this purpose, but I was wondering if 4.10's would be a little too extreme. Also, what is the stock axle ratio of the car now (again, 2001 Z28 auto.) Finally, what difference can I expect from gears in terms of E.T. , and how will they affect my driveabillity? Will I lose any gas mileage or will it remain the same? How many mph does one lose from the top speed of the car when going with 3.73's or 4.10's? Thank you guys in advance for taking the time to answer these questions.

 

3.73 for your auto. Do a search for lots of info on this subject. Here is a link for a gear calculator. Later>>>>

http://www.f-body.org/gears/

 

I have had 3.73's installed in my 2001 Z28 (A4) for about a year now, and most of my driving is done on the freeway. My gas milage has gone down about 2 to 3 miles a gallon, however the car is much more fun to drive. It is far more responsive upon acceleration, and IMHO, it should have been the gearing GM installed in this vehicle all along.

At one point I was strongly considering 4.10, however when I ran the gear calculater, it became brutally clear that above 60 MPH, in overdrive, any kind of down shifting of the car would put you over the redline.

I do not have the figures in front of me, however I now turn 2400 RPM at 72 or 74 MPH, and at 80MPH I am in the torque curve.

A torque converter will net you more gaines on your e.t. at the track than gears, however I feel their is also draw backs on using converters with 2.5 and up STR, on an already fragile rearend.

Look at the RPO sticker on the drivers side door, GU2=2.73 gears (2 series carrier), GU5=3.23 gears (3 series carrier). Another way to tell is to look at your driveshaft, is it rusted? if it is, it is "steel" and you have the 2.73 gears. If it is unrusted, it is aluminum, and was part of the performance axle upgrade, and you have 3.23 gears.

IF YOU HAVE THE STEEL DRIVE SHAFT, YOU SHOULD CHANGE IT TO AN ALUMINUM UNIT WHEN GOING TO 3.73'S, or you will experience vibration from the higher RPM's.

You do not need the HPP3 to recalibrate your speedo, I did it with the "SLP" speedometer recalibrater.

Hope this helps you out in some way.

SteveC

 

Thank you guys. SteveC, I have the GU5 option on my car indicating that I have the aluminum driveshaft. Are there any other precautions I should take before having these gears installed in regards to the rear end or any of the other driveline components? Also, do you know how many mph the top speed of the car will lose? I don't plan on topping the car out to see but I am just curious

 

wussa ****? I have a 98 m6 which had 3.42's. I've had 3.73's in for about 3 weeks now and im really really happy i haven't noticed a grand difference in gas milage, although im not really concerned with that. As for top end your not gonna lose much at all, U might not even notice a change at all. most i've driven this car @ is 128-130mph range, and i still feel as if i get there as quickly as before, You will notice a grand difference outta the hole, car became a beast, and traction problems get a little worse especially if u have a 6 speed, but all in all i higly recommend the upgrade. easy job to do, I did it myself, takes a bit of time cause you gotta shim properly or you will never get rid of the noise there after. If your gonna take it to a shop to get done... be sure it's a well known/respected shop with experience in rear axels, and besure they use the proper gear lube, i used mobil 1 full syntetic, it's already Gl-5 spec, so you don't need to add limited slip gear oil additive (although i did ne ways). good luck laterz

 

VetteThreat;

I purchased a "TA" girdle and stud kit, and my gears were cyrogenically frozen to make them harder. I used straight 140W dino oil for the break in (500 miles), then changed to Valvoline 85W-140 dino oil and added the GM posi additive.

DO NOT RUN SYNTHETIC OIL IF YOU HAVE AN AUBURN UNIT. You can use sythetic if you have the Zexel-Torson.

Use this handy gear calculater for the top speed difference:

http://www.f-body.org/gears/

Good luck on your gear change, Let the pro's do it.

SteveC