foggy

Working on a friends car. 03 6 speed. Ring & Pinion shot craps...
Debated over going to 3.73 or 3.90 gears. Decided to go 3.90's
Still in the break in process, so haven't gotten on the throttle hard yet...
But WOW !!! what a transformation
All the gears are actually usable now. And this thing just feels like a different car.

This is just an old man cruiser, so will never have dyno or track #s on it. But, If you are debating... GO for the steeper gears
I highly doubt MPG will change at all on highway trips, unless you like to set your cruise at 100 mph !

dskinsler83

Your friends car...is it a Vert, Coupe, or Z06?

Glensgages

almost 20 years ago, I went from the pathetic 2.87 gears to 3.73:1 in my '82 copue, best possible change I ever made to that car



fast-forward to today, and am thinking about a similar switch to my '03 A4 Z51 (3.15-geared) coupe



following, and eagerly awaiting more feedback on this topic

pit-man

3:90 great for the track but tons of wheel spin on the street on drag radials. Always having to peddle.
Gary and Rob have proven the 410 even better on the 60 foot times.
Pitt

foggy

It's a base coupe 6 spd
The difference is awesome

foggy

I have a 2000 A4 Vert.. I am thinking about going to 3.42 from my factory 3.15 gear ratio.
It's just a cruiser, so I'm not sure how that will affect fuel mileage at highway speeds since it's final gear is .70:1...
but I bet it would be quite a bit snappier around town.. IDK how people could stand the 2.73 base gear.. Must be a real dog
around town driving !!

4XLR8N

Have been debating the same thing for several years now...just don't want to wind up with gear noise, which seems to be an issue on a lot of gear swaps I have heard/read about. Will be interested to know if the new gears are as quiet as the factory ones...

STLSPARKY

I would recommend a 3.42 with an A4 unless you like not having traction and MPG suffering then go steeper lol
I had 2:76 or 2:67 in my A4 and I switched to 3:42 which helped quite a bit before I decided to swap in a 6speed
3:42 set still and I cannot get any traction until 3rd gear car makes 575rwhp

Glensgages

I'm having trouble, justifying the cost of going from the OEM 3.15 gears to 'just' 3.42, when 3.73 or 3.90 is the same price.

I'm lucky to put 3,000-4,000 miles each year on the car, so mileage isn't as big of a factor as it may be for other owners

Johnny Hardcore

If the gears are noisy they were not installed correctly. 4.10s in my MN6 just as quiet as stock. Made a world of difference with get up and go.

It also eliminated the drone from my Borla Stingers/ Kooks LTs and Xpipe while cruising in 6th. The RPMs are up just enough to keep the car out of the drone zone. That in itself was worth it and an added unexpected bonus after the swap.

pit-man

I agree, my 390 gearing has no noise at all. Could be a daily driver

02torchred

I'm there too with the A4 guys who think the 3.15 to 3.42 seems like a small difference on paper, however I've never heard someone not like it. Although could it be because some people don't like to say bad things after spending a good amount of money?

I'm wondering if the C5 does better with shorter gears. I wouldn't go any shorter than 3.42 because it would be screaming in 4th gear on the highway

heggsc5

Stock 3.42s make the car feel slow, I was never impressed from day one. 4.10s made street driving much more fun for me all around. Fresh R888s gripped great in 1st when I was still NA. Still manageable with an A&A kit.

robmiz

Hey Foggy...who did the rebuild? I know there’s Unitrax on the west coast.... and Murica performance in KY, I read is permanently closed...

I have spare differential that needs to be rebuilt. I would like to try 3.90 gears...

Thanks!

fastlenny

Is the jump from 3:42 to 3:90 that big on a 6 speed car?

wydopnthrtl

I'm a big fan of steep gears. I will say this though.. if your not concerned about cost a little better thing is to not go so steep on gears (like 3:42-3:73) AND loosen up the convertor.
IMO a run of the mill C5 w/auto I'd go 3:5-ish gear and a 2600 stall convertor.

PNW_C5Z

I've done larger gear jumps, but in trucks. I don't think it's a huge jump, personally. Enough to feel, yes...but it's not like you're going to all of a sudden be turning 4500rpm cruising on the highway.

heggsc5

That's the effective difference between base C5 and C5 Z06 gearing (for the first 3 gears). GM thought it was good from the factory for a C5 Z06 and I haven't heard a Z06 owner complain lol.

I went from 3.42 to 4.10 and it wasn't as large of a difference as people make it out to be. You probably won't notice a difference between 3.90 to 4.10 other than shifting a few mph later and gears lasting a few mph longer.

The largest difference is felt in the first two gears. If you have traction in first, it will blast through first in a hurry. 6th gear will also now be usable, but you'll only see a 300 rpm difference at cruising

~Josh

^ Actually every gear in a z06 M12 except 4th is shorter than the M6.

In my z shifting at redline from 4th into 5th is like shifting into 4.5. -rpm doesn’t drop a lot and car pulls great.

Some guys tag the M12 as a “magazine gearbox” but personally I love it for street driving.

Johnny Hardcore

Another thing to take into consideration with the steeper gear sets....if you've done heads and cam with a higher red line you'll also see major benefits with the gears as you have longer range between shifts. I've never run the 4.10s with stock heads and cam so no comment on likability on stock setup. I did drive my brothers 99 MN6 with just bolt ons and 3.90s and it made a noticeable difference in get up and go. The gears run through a bit quickly on stock red line under "normal driving conditions" but still worth the upgrade in my and his opinion.