Gearbox DHF, Long 5th Gear: Compatible Ratios?

Hello,
I'm looking for a longer 5th gear for my A4 AFN with a direct-shift gearbox (DSG) to improve fuel efficiency during economical driving.

In the gearbox overview http://www.dieselschrauber.de/GKB.html, I can find other gearboxes with a longer ratio, but I only want to change (or have changed) the 5th gear. So, which gears fit?

The DHF value is, for example, 28:41 = 0.683.
The DGW (presumably a measurement) is 27:41, which equals 0.6585, meaning it's approximately 4% longer.
The DPL is 24:40 = 0.6, which means it's 12% longer (is that too long?).

I think I've already searched through the entire forum, but maybe I missed something? I can't imagine that all gearboxes are so compatible that you can simply swap any pair of gears from one gearbox into another.
Perhaps I should also mention that I have never seen the inside of a gearbox before.

I would also be interested in hearing about your experiences with such a modification: does it actually save anything, for example, when driving at 140 km/h near a railway track?

Regards,
Udo.

Hello!

Unfortunately, I can't say for sure what works and what doesn't. However, it does bring some benefits, as you achieve the same power output with lower RPM and more torque, and the engine operates with higher efficiency. I think 12% is an exaggeration. The car still needs to be able to climb hills.

best regards
Jörg.

You can always turn back when you're going up a mountain!

But if the fifth one is already long, then it's probably too much.

For mine, 12% would be just right.

@Udo
Try using Ulf's DZR Excel file. You can find the relevant information on the third sheet.
'We're going to play around with all the numbers. There won't be huge savings, but it will definitely have a positive impact on everything.'

The gear ratio calculator turns out to be a great toy! I entered the weight and gear ratios of my A4, and it seems accurate. If I extend the 5th gear to 0.6, I still reach almost the same top speed, but at only 3600 RPM, which is fantastic. It just takes a while to reach the top speed (in the simulation), but maybe you could 'help' it along with a small adjustment.

Zum Beschleunigen und bis ca. 160km/h gäbs dann ja noch den 4. Gang
'Driving at 130 km/h with the engine running at 2500 RPM in fifth gear – that would be something I'd enjoy.'

The question remains: Which gears will actually fit?

- Udo


P.S.: I once had 205/65R15 tires registered for my old A4 (may it rest in peace), which is approximately a 3.5% increase in size compared to the 205/60R15 tires. After that, I didn't achieve the same maximum speed according to the speedometer, but the speedometer was also not showing as much error before. The fuel consumption seemed to remain the same ==> a 3.5% fuel saving .

Hi Udo,

The DPL transmission is not the same series as the DHF transmission.
I can't say for sure, but I don't think that fits.

Regarding the DGW (presumably a part number), I'm stuck. Unfortunately, according to AKTE (a parts catalog software), I can only see that it exists.
"It should be available for the Passat models from August 1997 to August 1998, and for the A4 models from August 1997 to December 1997. However, if I then..."
I can't find the electrical components (ET parts).
I am unable to find the specified translation of 27:41 anywhere, and...
The question is whether the 4% increase is actually worth it...
Okay, and I haven't found a longer axle ratio than your 37:10 either .

Best regards, Frank.