Can someone out there tell me what an A4 with a 2.73 gear should be turning at 70 MPH?

I went for a little drive on the interstate eariler for the first time since picking up my C5 and I was twisting between 2400-2500 at 70 MPH accordning to my GPS. That just seems a little high for me with a 2.73 gear but I could be wrong.

 

I'll have to double check later today but I think I'm only around 2200 same tranny/rear

 

what do you mean according to your GPS?

What does the speedometer and tach say?

 

I mean that the speed was verified with my GPS instead of relying on the speedometer, The RPMS were according to the tach...my gps doesnt do RPMS...

if your at 2200 maybe my tach is a little off

 

75 mph in 3rd gear on an A4 3rd gear is a 1:1 ratio 4th is an overdrive don't use or the math won't work!!
2.73 rear end will turn 2730 rpm
3.15 rear end will turn 3150 rpm
3.42 rear end will turn 3420 rpm
3.73 rear end will turn 3730 rpm
4.11 rear end will turn 4110 rpm

See the pattern.. Same results on a 6 speed.. Test must be done in 4th gear which is a 1:1 ratio overdrive gears are 5th and 6th not ot be used for this test

 

Thanks!

Ill give her another run and check it out in 3rd

 

Actually its 75mph sorry!!!!
C5 transmission ratios (by gear):

MN6: 3:42 rear (Standard)

1st 2.66

2nd 1.78

3rd 1.30

4th 1.0

5th .74

6th .50

Rev. 2.9



MN12 3:42 Rear (Z06)

1st 2.97

2nd 2.07

3rd 1.43

4th 1.0

5th .84

6th .56

Rev. 3.28



A4: 2.73 Rear

1st 3.06

2nd 1.63

3rd 1.00

4th 0.70

Determining your C5 A4 rear axle ratio

Look at your option list. If you look in your glove box there is a sticker with all codes on the inside of the glove box door. The 3.15 performance axle ratio option is code G92. For '99 and earlier it should be listed on the underside of the left-hand storage well cover:











GU2 2.73 ratio

G92 - 3.15 ratio

GU2 - 2.73 ratio

GU6 - 3.42 ratio (manual tranny only)

Place your A4 into 3rd ( third) gear and get on the highway. At a constant 75 mph (making sure the TC has locked) read the rpm value; then divide it by 1000. (This also works with the six speed manual transmission using 4th (fourth) gear):

examples:

2730 RPM........ you have a 2.73

3150 RPM........ you have a 3.15

3420 RPM........ you have a 3.42 (not a factory available ratio with the A4)

3730 RPM........ you have a 3.73 (not a factory available ratio)

3900 RPM........ you have a 3.90 (not a factory available ratio)

4100 RPM........ you have a 4.10 (not a factory available ratio)

 

get under the car and look at the rear end differential. It will have a small metal tag that will say GETRAG 2.73 or GETRAG 3.42 You don't have to jack the car up as its on the rear of the differential

 

definitely high. i'm guessing you have 3.73's or 3.90's in there.

just replaced my 2.73's with 3.42's. at 70 mph the rpms changed from 1600 to 2100.

jeff

 

Befor gear swap 2:73 at 70mph was 1650 rpm Now I am at 2200 rpm with 3:42

 

3red (THIRD) gear, 75mph, rpm = rear end ratio

 

http://www.tim-yvonne.com/mikemercury/ratio.htm

 

Well Finally got a day off work and some time to really investigate.

The glove box code is a GU2, so I should have a 2.73 but I just wasn't buying that car had way too much azz and twisted too hard on the interstate for me to be happy with that answer.

Next I popped up under the rear of the car to see the tag on the rear end, well it said 3.15, so now I know its been changed but that still didnt seem right to me, so as I scan around with my flashlight I notice someone has written 3.90 on the rear end cover....

SO i open up the garage and deicide its time for another stroll down the interstate in 3rd gear...I get her out on the interestate and level off at 75 mph and sure enough 3900 rpms...

Thanks to all the replies and help given, apparently I have 3.90s in the car...lol...

 

I guessed correctly - what do i win?

glad you found out what you have, but they are kinda steep gears for a street car.

jeff

 

Yea you hit the nail on the head. They really aren't that noticable IMHO unless you are on the interstate with daily driving. Well of course that is unless you turn off the traction control and grab a hand full of throttle...then you notice them.