Final drive ratio

[pluciano]

Hey guys,

I've done some researching and have found that Stasis offers the torsion 4:1 center differential. I am looking for something that changes the final drive ratio in favor of quicker acceleration (such as a 4.11 final drive ratio). Does anyone know of what I could buy to change the final drive gearing to achieve quicker acceleration?

Thanks,
Paul

[Justincredible]

if you have a manual you already have a good 3.83 gear auto 3.55. Due to the fact that it is a AWD you would need to change the front and rear gears. So not easy

[JB_ImolaS4]

I would be interested this as well

[pluciano]

if you have a manual you already have a good 3.83 gear auto 3.55. Due to the fact that it is a AWD you would need to change the front and rear gears. So not easy

Thanks, I have a manual with the 3.889 final drive ratio. I'm just looking for aftermarket solutions that can increase the car's acceleration through an increased final drive ratio.

[chaos2984]

do they even make a different ring and pinion ??

[Swanky]

http://www.034motorsport.com/index.php?cPath=25_2719

take a look at these... they seem to have a 4.11 rear as well as front diff options but not sure if they are specific to the s4 or a4 or what...

[JB_ImolaS4]

http://www.034motorsport.com/index.php?cPath=25_2719

take a look at these... they seem to have a 4.11 rear as well as front diff options but not sure if they are specific to the s4 or a4 or what...

Strange, when I go to stasisengineering.com and punch in my vehicle specs, the only products they offer (on their website) for the 2004 S4 are the Alcon brakes and the Stasis SL / MS coilovers. This 034 site is showing the Torsen and the Limited Slip Rear Differential as being Stasis products.

I tried changing the year of the spec vehicle on the Stasis website to see if additional products would come up for the 4.2 V8. 2005 had the same line-up as the 2004. Selecting 2006-2008 will toggle the exhaust (for the B7, makes sense), but no differentials.

I'm curious why neither the Torsen nor the Limited Slip Rear Differential show up for the V8 S4?

[Swanky]

Strange, when I go to stasisengineering.com and punch in my vehicle specs, the only products they offer (on their website) for the 2004 S4 are the Alcon brakes and the Stasis SL / MS coilovers. This 034 site is showing the Torsen and the Limited Slip Rear Differential as being Stasis products.

I tried changing the year of the spec vehicle on the Stasis website to see if additional products would come up for the 4.2 V8. 2005 had the same line-up as the 2004. Selecting 2006-2008 will toggle the exhaust (for the B7, makes sense), but no differentials.

I'm curious why neither the Torsen nor the Limited Slip Rear Differential show up for the V8 S4?

maybe they are a reseller and have old stock laying around... i dont think people change the gear ratio too often on the s4 but i could be wrong

[jaybquick@JHM]

The B6/B7 S4 transmission is totally different than the older B5 S4 transmissions you speak of. The parts are not interchangeable.

The B6/B7 S4 uses an 02A-03A trans made by getrag. The older 01E that was in the B5 S4 is different and had been used since the early 90s.

Also if you change the trans front gear set you will also have to change the rear end gearset. Beside that you will have to find a way to reprogram the dash to display your MPH properly.


The B5 S4 does have a 4.11 final drive and the B6/B7 S4 has a 3.89 final drive. Yes the final drive is lower but if you compare the ratios, the B6/B7 S4 has lower gears in the trans. So if you multiply out the each gear ratio with the final drive the overall effective ratio is about the same. Also the B6/B7 S4 has a taller wheel/tire combo.

Here is how the ratios stack up

B6/B7 S4 transmission
1st = 3.66
2nd = 2.05
3rd = 1.46
4th = 1.13
5th = .92
6th = .78

Multipy each gear with the final drive ratio of 3.89 for the effective ratio.


B5 S4 transmission
1st = 3.50
2nd = 1.89
3rd = 1.32
4th = 1.03
5th = 0.81
6th = 0.68

Multipy each gear with the final drive ratio of 4.11 for the effective ratio.


If someone wants to do the mathc and figure out the effective ratios and also compare the overall tire height you will see they are darn close. The B6 S4 also has a torquey V8 that after my experiences drag racing one does not need a lower gear ratio. You want the car to finish at high rpm at the top of 4th. Right now it is decently high in the rpm band and with a suercharger or nitrous you would almost end up having to shift this car into 5th to finish the quarter mile and not hit the rev limiter.

Bottom line, I wouldn't bother, it has excellent ratios for what it is. Plus your highway MPG would suffer with lower gears.


Hope this info helps.

[jaybquick@JHM]

maybe they are a reseller and have old stock laying around... i dont think people change the gear ratio too often on the s4 but i could be wrong

I do have plenty of B5 S4 4.11 ring and pinions from parts trannys here. But only a couple rear diffs. But like I said before they are different transmissions and different rear ends. With some machining who know.

[Swanky]

Here is the gear ratio analysis for the b6/b7 s4 vs the rs4 I did a few months back if anyone cares... you can see the rs4 has the 4.11

-------------------b6/b7 s4 --------------------------------- rs4------------------------------

[jaybquick@JHM]

We have now done the research and found that we can get a set of 4.11 gears for the front diff (in the trans) and the rear diff.

This would be a major job and include a complete teardown on the trans.

We will hopefully be doing this swap on our in house B6 S4 we just acquired to help maximize it for the drag strip. We also plan on swapping in a diesel 6th gear for better cruising RPM to more than offset this change.

Hope this update sheads some light.

[BigJS4]

If you want to do it the easy way, just change the tire circumference...

It is the easiest way to alter the "final drive" ratio without having to rip out the diffs.

There are man calculators online to figure out what tire size you will need to get to the proper final drive ratio you want.

Just remember, this will effect your speedo.

As per the calculator above, the B6/B7 S4 could benefit on the drag strip from a lower final drive ratio. Since these vehicles are AWD and traction isn't a huge issue... you could use a 4.XX to get more torque to the wheels in a lower gear there by lowering the top speed in each gear allowing you to reach the sweet spot in the powerband quicker and keeping it there in each shift. On the drag strip you don't need a 3rd gear that hits 95mph and a 4th that hits 123mph.

Personally, I think gearing is one of the best ways to optimize a vehicle. It's like cutting weight on a car also. Though it does not add any power, it makes the vehicle "faster". Finding the proper gearing ratios for your type of racing on a vehicle is really where it is at. I have cut several tenths off of vehicls just by messing with the final drive ratio on a car.

To JHM... with a 4.xx final drive ratio (either through ring/pinion or tire size change), your 13.03 would easily have been in the 12's. Good luck with your next steps.

[jaybquick@JHM]

If you want to do it the easy way, just change the tire circumference...

It is the easiest way to alter the "final drive" ratio without having to rip out the diffs.

There are man calculators online to figure out what tire size you will need to get to the proper final drive ratio you want.

Just remember, this will effect your speedo.

As per the calculator above, the B6/B7 S4 could benefit on the drag strip from a lower final drive ratio. Since these vehicles are AWD and traction isn't a huge issue... you could use a 4.XX to get more torque to the wheels in a lower gear there by lowering the top speed in each gear allowing you to reach the sweet spot in the powerband quicker and keeping it there in each shift. On the drag strip you don't need a 3rd gear that hits 95mph and a 4th that hits 123mph.

Personally, I think gearing is one of the best ways to optimize a vehicle. It's like cutting weight on a car also. Though it does not add any power, it makes the vehicle "faster". Finding the proper gearing ratios for your type of racing on a vehicle is really where it is at. I have cut several tenths off of vehicls just by messing with the final drive ratio on a car.

To JHM... with a 4.xx final drive ratio (either through ring/pinion or tire size change), your 13.03 would easily have been in the 12's. Good luck with your next steps.

Exactly. We are aware of this, but as a business we are trying to do everything straight up with no tricks. If we did go this route we would share however. We are going to concentrate on traction at this point.

You are correct about the speedo being off when doing tires. However if the trans and rear diff had their final drive swapped with 4.11s you would NOT have a speedo issue. Luckily gets the vehicle speed on these cars from the wheel speed sensors already used by the ABS system. The actually don't have a speed sensor in the trans like the previous B5 S4.

[TheMaverick]

We have now done the research and found that we can get a set of 4.11 gears for the front diff (in the trans) and the rear diff.

This would be a major job and include a complete teardown on the trans.

We will hopefully be doing this swap on our in house B6 S4 we just acquired to help maximize it for the drag strip. We also plan on swapping in a diesel 6th gear for better cruising RPM to more than offset this change.

Hope this update sheads some light.

I might be in the minority here ... but I woudl actually be interested in just swapping out 6th to get better MPG while just cruising down the highway. Easy or not? Know of any options? Sounds like that is what you are suggesting here.

[beemercer]

I might be in the minority here ... but I woudl actually be interested in just swapping out 6th to get better MPG while just cruising down the highway. Easy or not? Know of any options? Sounds like that is what you are suggesting here.

There is a thread from a while back discussing swapping in the diesel 6th gear, search will find it.

[jaybquick@JHM]

I might be in the minority here ... but I woudl actually be interested in just swapping out 6th to get better MPG while just cruising down the highway. Easy or not? Know of any options? Sounds like that is what you are suggesting here.

Unfortunately with the 0A3 transmission in the B6/B7 S4/RS4 6th gear is buried way inside on the countershaft. The older 01Es which we have done them for in the past is near the end and easy to swap.

I feel it would be a great upgrade if you were already paying to have your trans rebuilt (a service we offer). Since the labor to replace 6th gear is the same.

[S4Sumi]

If you want to do it the easy way, just change the tire circumference...

It is the easiest way to alter the "final drive" ratio without having to rip out the diffs.

There are man calculators online to figure out what tire size you will need to get to the proper final drive ratio you want.

Just remember, this will effect your speedo.

As per the calculator above, the B6/B7 S4 could benefit on the drag strip from a lower final drive ratio. Since these vehicles are AWD and traction isn't a huge issue... you could use a 4.XX to get more torque to the wheels in a lower gear there by lowering the top speed in each gear allowing you to reach the sweet spot in the powerband quicker and keeping it there in each shift. On the drag strip you don't need a 3rd gear that hits 95mph and a 4th that hits 123mph.

Personally, I think gearing is one of the best ways to optimize a vehicle. It's like cutting weight on a car also. Though it does not add any power, it makes the vehicle "faster". Finding the proper gearing ratios for your type of racing on a vehicle is really where it is at. I have cut several tenths off of vehicls just by messing with the final drive ratio on a car.

To JHM... with a 4.xx final drive ratio (either through ring/pinion or tire size change), your 13.03 would easily have been in the 12's. Good luck with your next steps.

Sorry a little off topic, but is that what 4th gear maxes at on the stock gearing for a b7 s4 -- 123?? I'm just wondering how fast I went on a straight away at Thunderhill last week

And wow..swapping in the deisel 6th gear.. has anyone done it?

[jaybquick@JHM]

Sorry a little off topic, but is that what 4th gear maxes at on the stock gearing for a b7 s4 -- 123?? I'm just wondering how fast I went on a straight away at Thunderhill last week

And wow..swapping in the deisel 6th gear.. has anyone done it?

Depedning on the chip, tire diameter and your redline setting 120 to 125mph is the range.

We should have one swapped in by the end of the year and will find out if there are any issues with the computer system seeing the wrong RPM for a given speed. Only 1 way to find out.

[jaybquick@JHM]

Also we did some more research on this.

We need the following to complete a 4.11 swap.

A rear end out of a B7 RS4 or a rear end out of a B6 A4 1.8t 6-speed car with the 02x manual trans. About $200 to $400 from a wrecking yard.

Then the ring and pinion from an RS4 trans for the front. About $1000 plus labor to dissasemble the trans and reset the pinion depth and the ring gear backlash properly. Probably $1,000 labor with the trans already out.

We are possibly going to try this on our in house car as well, but we are looking for cheaper alternatives.