5-speed question
 

just got an 02 A4 quattro 5speed and its my first manual car, i was wondering when im in 5th gear going down the highway at 75mph, how many RPMs should i be at?? i was up to 3400 and that just seems to high, but idk. help?

that's about right. I roll just under 80mph on the freeway and the tach sits around 3800. Thought it was high when I first started driving it too but its all good as long as it stays solid when you step on it and you don't get any slippage out of the clutch.

+1 to what MKE_Audi says; the 5-speed box is just geared really short.

For the curious, a listing of various A4 gear ratios is here:

Gear Ratios

The 6 speed is slightly taller in every gear, plus it has 1 more gear (final drive is the same). The tall 6th gear should result in significantly lower RPM (and therefore at least somewhat better fuel economy) at highway cruising speeds. I was expecting to see slightly closer ratios, with 1-5 being a little bit shorter than the 5-speed and only 6th being taller, but I guess that's not what Audi decided on.

yeah i usually cruise at around 85-90 and get it over 4,000 rpm but everytime i get gas i calculate my gas milage and its always around 24.5-25

That is correct. That would be high for a V6 or V8 but not high at all for a 4 cylinder.


Which is good gas mileage for driving those speeds.


Sorry to tell you this but a lower rpm at the same speed is not going to increase your gas mileage. The lower the rpm the less power your little 4 cyilinder is making while out of boost, this means to hold that same speed you would have to use more throttle which means more boost(less vacuum) which means more fuel is being sprayed into the engine. The larger displacement engines run at lower rpms because they are spinning more parts and feeding more cylinders with fuel. Just look at how bad the MPG is for the V6 cars including the 2.7t vs the 1.8t with its much higher rpm. Audi even listed the MPG for the B6 A4 1.8t 6 speed lower vs the B6 A4 1.8t 5 speed, only difference was the gearing.

The A4 5 speed does have shorter gearing, but that helps increase acceleration. Put a transmission with taller gearing and your car will just end up feeling even slower then it did with the stock transmission. I have already proved that at the track, 2.8 5 speed(taller gearing) vs 1.8t 5 speed (shorter gearing). With the 2.8 gear box the car went around 11.3 at high 120's, with the 1.8t gear box the car went 10.6 at 135+.


This is why I still run the stock 5 speed 3rd-5th gear, I put in slightly taller 1st/2nd gear out of a Audi Coupe 4.11 01A transmission.

Your explanation would seem to indicate that you'd get better fuel economy by running 3rd gear (approx 5300 RPM) for 70 MPH cruising than 5th gear (approx 3300 RPM), but perhaps that just means I'm misunderstanding you somehow?

For the record, I'm well aware of the acceleration benefits of shorter gearing (mechanical advantage). That's why I said I was surprised by the fact that the 6-speed is taller in every gear; I expected 1-5 to be shorter and closer together than the 5-speed in order to facilitate that.

Well the V6 6 speed is pretty much geared for a car that has a much larger power band.

If you look at the A4 2.0t gearing you will notice that it has nearly the same 1st-4th as the A4 1.8t 5 speed, but has a slightly taller 5th and the extra 6th gear.


B5 A4 5 speed vs B7 A4 6 speed (both use 3.889 final)
1: 3.778 vs 3.667
2: 2.176 vs 2.053
3: 1.429 vs 1.423
4: 1.029 vs 1.032
5: .838 vs 0.800
6: none vs 0.658

B5 A4 5 speed
B7 A4 6 speed

Another Audi 6 speed that has better gearing then the B5 S4 is the one found on the B6 S4 4.2, also has a 3.889 final.

B5 S4 6 speed
B6 S4 6 speed

Mike: do you have the gear ratios, final drive handy for B5 S4 (6 spd), B6 A4 1.8T 6 spd and B6 A4 1.8T 5spd ?

How does overall gearing in high gear with respective final drive compare?

And in laymen's terms, the respective RPM at 80 mph?

B5 S4 6 speed
3.5 (14.39)
1.889 (7.77)
1.231 (5.06)
0.967 (3.98)
0.806 (3.31)
0.684 (2.81)
Final drive ratio 4.111


B6 A4 1.8t 6 speed
3.667 (15.08)
2.053 (8.44)
1.37 (5.63)
1.032 (4.24)
0.8 (3.29)
0.658 (2.71)
Final drive ratio 4.111


B6 A4 1.8t 5 speed
Gear ratios (overall):
3.778 (14.69)
2.176 (8.46)
1.429 (5.56)
1.092 (4.25)
0.838 (3.26)
Final drive ratio 3.889


You can use this site for RPM/MPH using the gearing above, this is already setup with the B6 A4 1.8t 6 speed gearing.

The RPM change in the same relationship as the overall gearing for a given speed?

Example:
2.71 = 2000 rpm
2.81 = 2074 rpm
3.26 = 2406 rpm

Correct?