TDi Gear Ratios
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1st Gear
Joined: Apr 2011
Posts: 45
From: Leonardtown, MD
TDi Gear Ratios
I've been trying to educate myself on the significance of various engine specifications. (At least since I decided to spend $36K+ ordering a new Audi) The nice thing is that most of the information is out there and is no more difficult than my high school physics or algebra class. But one thing about the Audi A3 TDi has me confused, and I can't seem to find a straight answer on the web.
The gear ratios of the 2010/2011 A3 TDi are like this:
1st - 3.462
2nd - 2.050
3rd - 1.300
4th - 0.902
5th - 0.914
6th - 0.756
reverse - 3.989
Final Drive - 3.043
The number that jumps out is the 5th gear ratio. Since the speed of the engine relative to the speed of the tires is the multiplication of the gear ratio and the final drive ratio, the engine in the 5th gear would appear to be running at higher RPMs than the 4th gear, which makes no sense. The first thought is why even have a 5th gear if they are so close.
After satisfying myself that it is not a typo of some kind, I uncovered the concept of a dual final drive ratio, but I am not clear how that is possible. And assuming it is possible, I can't find information on what the second final drive ratio for this engine is. (Though I did find information on the TFSI engine 4.06/3.14. The same site when switching to the TDi just says "Final Drive Ratio: Yes")
It appears from what I have read that the 5th, 6th and reverse gears run off a different final drive ratio. What exactly is going on? Does anyone know what the other drive ratio is, whether the number that Audi provides is for the 1-4 gears or the 5-6-R gears?
The gear ratios of the 2010/2011 A3 TDi are like this:
1st - 3.462
2nd - 2.050
3rd - 1.300
4th - 0.902
5th - 0.914
6th - 0.756
reverse - 3.989
Final Drive - 3.043
The number that jumps out is the 5th gear ratio. Since the speed of the engine relative to the speed of the tires is the multiplication of the gear ratio and the final drive ratio, the engine in the 5th gear would appear to be running at higher RPMs than the 4th gear, which makes no sense. The first thought is why even have a 5th gear if they are so close.
After satisfying myself that it is not a typo of some kind, I uncovered the concept of a dual final drive ratio, but I am not clear how that is possible. And assuming it is possible, I can't find information on what the second final drive ratio for this engine is. (Though I did find information on the TFSI engine 4.06/3.14. The same site when switching to the TDi just says "Final Drive Ratio: Yes")
It appears from what I have read that the 5th, 6th and reverse gears run off a different final drive ratio. What exactly is going on? Does anyone know what the other drive ratio is, whether the number that Audi provides is for the 1-4 gears or the 5-6-R gears?
1st Gear
Joined: Jul 2009
Posts: 145
You probably have to dig around for the dual final drive ratio, since it is different for every engine. Some sites will display an adjusted gear ratio based on a single final drive ratio. But you won't know if it is accurate unless you verify it with the original gear ratio and its dual final drive ratio.
Maybe it would be easier if you just drive the car and see what the speed is at each gear and a fixed RPM.
Maybe it would be easier if you just drive the car and see what the speed is at each gear and a fixed RPM.
Thread Starter
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1st Gear
Joined: Apr 2011
Posts: 45
From: Leonardtown, MD
Now that I have had the car for a week and have put a few hundred miles on it, my tests would seem to indicate that the final drive ratio for the 1-4 gears is identical to the TFSI engine at 4.06.
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