75TA

I bought my son a 1999 Trans Am with automatic. We are slowly modifing it to get more performance. It has a aftermarket lid, Cat back exhaust, 160 deg thermostat and cold air kit. He just purchased long tube headers, but can not install until I get my engine back in my 75 TA - it will get a tune-up after the headers. The next upgrade was going to be an LS6 intake. However, today we learned that his rear end needs a new gear set (ring gear lost a couple teeth) - under warrantee (4,000 mile left). It was a 2.73 ratio. I have searched and found that most indicate a 3.73 gear set, but I see a few indicate that they are using 3.42's. Which is the best - the car does see the highway. At this point we are not going to change the whole rear, but it will be rebuilt and I was told I could select different gears. Other upgrades for the future are a converter and cam.

sreve

iTrader: (3)

gears , stall , cam should all match. think of your goals for the car.
many proven combos out there. search is your friend.

GIVE EM' THE BIRD

iTrader: (1)

3.73's. highway or whatever u will still get around 20mpg.

SS_Shanker

Recently put 373's in my 99 SS with an A4. 260 miles to my last tank while beating the crap out of it. Those gears wake that car up somethin fierce. Can't wait to get it to a track now. It is not even the same car with those gears however still perfectly fine as a daily driver. Overdrive improves as well as it is now a useable gear for acceleration once 3rd runs out more fun on highways.

2500RPM at around 75-80mph in OD.

Best money you can spend. You should also buy the programmer for the car to reset the speedo for the new gears (about $400).

IZRED

A guy I know, he replaced his stock gears in his suburban with 3:73's n that heavy thing hauled some ***. He said he basically got the same MPG too.

COD02SS

STock gears and a yank 3200

DANOZ28

iTrader: (1)

hello, welcome! an article "ls1 do's and donts" recommends 3:73s for an auto (A4) , i may go conservative with 3:42s. (should be plenty unless you live at the track) basically SFC sub frame connectors, air lid, catback, longtubes (if they meet emmisions) ,LCA'S lower control arms (for traction) and panhard bar. torque converter (a4), sticky tires. if you'd like to pm me a fax # i'll send you the article. good luck!

Rhedalert

iTrader: (21)

I'm going with 3.42's since I'm 80% highway/commuter

Juicedz28

i have 3.42's and there good but im going to swap to 3.73's. And my car is a daily driver i just want to see that better gear ratio when im at the track or on the street.

djsanchez2

iTrader: (14)

I went 3.42's alot better pick-up, while retaining civil gas milage.
3.73's might be a bit much unless you are gonna drag race it alot.

INMY01TA

iTrader: (1)

Lame. I went 4:10s in my M6, I commute via highway every day and it didn't drop my mpgs even 1 mile per gallon.

5_02ls1

iTrader: (20)

373s are not to much gear....lol...when i was just boltons with 373s the car got close to 25mpg and was a blast to drive on the street.....bout wish id a left it that way......

ONEBADASSWS6

So how much do you average, MPG wise??

gyrene2003

All i can say, is yes i drag race my car, like once or twice a year, thats it and i cant understand why every with autos never does 3.90s, i did and i couldnt imagine going through all of that trouble for that kind of small jump, seriously, its not bad at all when im not ***** deep in it as far as gas milage, and if u do drag race, look at me, new member to the 12 second club as of this weekend going from 13.298 stock to 12.748, thats over half a second, .55 to be exact! I cant think of another bang for the buck mod (next to a stall) that will give u such a drastic jump for so cheap! Do 3.90s and never look back!! Screw 3.73s!

02 wife

I have 3.42's and love them!

gyrene2003

WIMP! Motive 3.90s and a Yank SS3600!

00blacksstallion

iTrader: (1)

Screw it and go 4.10s since you have an M6. You won't be dissappointed

75TA

Thanks for all the responses. By the way, my sons car is an automatic (A4) so 4.10 for him are not an option as this is a daily driver and will see little track time - if this changes over time, then a 9 inch or 12 bolt will go in with 4.10s. The car that will see more track time will be my 75 TA.

Is there any reliablity difference between 3.23, 3.42 and 3.73 in a ten bolt rear end.

johnh

iTrader: (1)

I don't think you're getting 25 mpg doing 70-80 mph on the highway with 3.73s. Maybe if you drive 55mph.

I have 3.73, and it's not a DD, around town not much difference in mileage..big difference in power over the 3.23s I had. A bit of difference on the highway....so if you plan on alot of highway driving chose the 3.42 or 3.23 as a good compromise.

CAMAROZ28SS

iTrader: (5)

get 3;73's