[Audi5jim]

Anyone have a .681 5th gear installed? At 80 mph, what does your tach read? 80 mph on my stock trans/5th gear is about 2700-2800ish. Before I install my .681 gear set, I was just curious about how much my tach will drop while highway cruising at this speed...

*80 mph was just an example speed I took note of today, any other mph you would like to give me would be fine.

 

[chittychittybangbang]

See this table. It applies to all 1998-2003 TDI. The pumpe duse 2004-2005 had a slightly different 5th gear and final drive. It used a 4.235 final drive and a .744 5th gear.

 

[Audi5jim]

Oh you're good! Thank you very much! That is perfect.

 

[chittychittybangbang]

Also, see this tire size calculator. You can even change the wheel, tire, 5th gear, and final drive to see RPMs.

http://www.venommotorsports.com/library/tirewheelcalculator.asp

It's way better than the miata tire calculator

 

[Audi5jim]

Great info! I just posted that link to my Audi forum.

Thanks!

 

[Fluid]

Wow, that tire calculator is great! But I wonder how accurate some of the calculations are. For example, it calculates tire and wheel inboard/outboard difference. Tires with thin sidewalls and which are put on wider wheels get stretched. Tires with high sidewalls and which are put on thinner wheels get bulged out. This could make a difference in clearance. It's possible to measure tire tread differences but harder to measure tire sidewall differences.

 

[freerider]

I doubt that it makes that much difference between a stretched tire and bulging tire. How much are we talking, 5 mm per side? 1 cm per side, 2 cm total? I would think that inflation pressures could make as much difference if you're that close to rubbing.

 

[MAXRPM]

I doubt that it makes that much difference between a stretched tire and bulging tire. How much are we talking, 5 mm per side? 1 cm per side, 2 cm total? I would think that inflation pressures could make as much difference if you're that close to rubbing.

I have 2 TDI's , both cars have the same 195-65R-15 Tires, different brands, and just by having different brands on the tires ,it makes a difference in MPG my golf has Eagle and has lower MPG than my Jetta that has Bf Goodrich, so I am 100 % sure that by putting wider tires, it would defently have an impact on the MPG, that is why some people prefer specific brand of tire for MPG, I heard that nokians and Michelin are good choices, I am going to try them out next time .

 

[Audi5jim]

I decided to return my .681 5th gear for the .658. With a 2% difference between the two, I might as well go for the taller of the two. I'll be installing it this weekend and I'll report back. I have been getting consistant 800+ miles per tank with a best of 833.4/54.1 mpg.

 

[grizzly]

IMO, the .68 is better because that 2% difference puts a bit more load on the engine and lets you climb hills with no problem. I have no idea how the .65 is but the .68 w/chip is just right, IMHO.

 

[Audi5jim]

Let's not get your typical daily commute geographics in the way here. I am thinking about this all the time and will say that MY commute will benefit from the .658. Now I'm not saying that the .681 would not also be beneficial to my commute, but if I have the geographics for either, I may as well go for the taller...no?

 

[strike3]

I'd be interested in hearing what the rpms are, how you like it, fuel economy changes, etc. I hear that the gap from 4th to 5th with the shorter gear is noticeable so I wonder what a taller gap will be like.

 

[Audi5jim]

I will certainly let everyone know. I will be doing this mod this afternoon when I get home from work. As of right now, driving 55 mph puts the tach between 1800/1900 rpm and at 65 mph it's about a needle width past 2200 rpm.

 

[Audi5jim]

OK, the .658 5th gear is in and I took it for a test drive. 55 mph now drops the tach to about 1600 rpm and 65 mph is now in the 1900/1950 range.