Pontiac GTO 2004-2006 - 2004 GTO rear gear options and results? Any takers?

Hey guys Im thinking about getting some 3.90s thrown in the rear, is this the only ratio we have availabe? It seems to be the only one I can find. Also is it worth the swap? How much of a difference is it from the 3.46 to the 3.90? Lastly how did it affect MPG for you? Thanks, just fishing for next mod lol.

3.91's** :)

I've driven a few auto cars with 3.91's and it's a little much on the street, more race car status.

Do you have a stock stall converter?

If so I'd do an aftermarket one first, maybe some freshened up trans internals.

I love them. They really wake the car up. I have my rebuilt pumpkin with Aussie 3.91's for sale in the classifieds.

Im in the process of building up my center section with the newer and less expensive US Motive 3.91s from GForce1320. the gears are about 450$ vs 650$ (roughly) for the Aussie gears.
I debated for a while about whether i wanted to do this or not, and the fact that the new 1LE camaro that is coming out is going to have 3.91s in it from the factory helped me make up my mind. Our cars are heavy and a little extra gear helps them feel a bit more nimble and also keeps the gear spread a bit closer for spirited driving.
Many I have talked to say cruising mileage can stay about the same if you are careful.. but that ripping around town can get expensive at the pump.
If you are having a shop do the work you are looking at the price of the gears, ~350$ labor, a master install kit 150$ and any little items the diff may need while apart. those were #s from my 3 quotes.
Hope this helps.
--Glenn
Edit: there are 3.70 and 4.10 ratios offered too. Since you are A4, i have seen it recommended to use 3.70s.
hit up gforce1320 or complete street performance for options and prices

I literally just got my swap done. I love them

Yeah stock stall for now but will be PTC 3000 soon. Thanks for the quick replies I appreciate it. Guess I'll check those places out and prolly go with the 3.70. Too bad it's a DD 4.10 sounds fun.

Love my 3.91's on an M6 but would probably hate them on an A4. Definitely go with 3.73's. My Motive 3.91's make a tiny bit of noise, installer said that it was normal and the pattern and backlash were good however.

Anyone feel up to making a complete grocery list for a gear swap? I just need to see what i'm looking at cash wise.

gears 450-650, install kit 150, side bearings 50, oil 12, intall price 600-1200, should be close, give a sponser a call they can help alot. good luck.

I put in Australian made 3.73 gears and liked them. Quiet. No difference in gas mileage.
I put in American made 3.91 gears and they whine a little. Lost maybe one mpg city/highway.

Both ratios will get the car moving well. The 3.73s are a nice city/highway gear.

Go 4:11`s or go home! lol

Hows this?
http://www.ls1gto.com/forums/showthread.php?t=320506
Sakeunited:
here ya go

M6 rpm (approximate)

3.46s @ 65 mph = 1650 rpm
3.70s @ 65 mph = 1760 rpm
3.73s @ 65 mph = 1780 rpm
3.91s @ 65 mph = 1860 rpm
4.10s @ 65 mph = 1950 rpm

Yeah stock stall for now but will be PTC 3000 soon. Thanks for the quick replies I appreciate it. Guess I'll check those places out and prolly go with the 3.70. Too bad it's a DD 4.10 sounds fun.

3.73's are very good for a daily driver.
I changed from these to 4.1's two years ago, yes mileage will suffer but they are so much faster;)

I was going with the 3.73s because I take it on every day driving really. I just do not know were to buy them or what brand.

Just did the 3.91's this past weekend. I barely notice them just driving around and honestly they aren't as bad on the hwy as I thought they would be. They def make the car pull a bit harder. This is a 10k+ mile a year dd as well.