Did a writeup on doing a 4:1 diff mod (A.K.A. Washer Mod) on a facelift (01) A4

**GetBoosted84** · 10-13-2010 06:05 PM

For anyone that doesn't know about this mod... here's a brief overview:
This mod takes a differential that could only send 2 times the torque of the other end of the car that is slipping up to 4 times the torque of the other end of the car that is slipping. It will allow you to send upwards of 80% of the torque to the end that is slipping. This is useful in situations like an auto-x where you are attempting to make it around a turn faster and normally once you loose traction, you will continue to go straight whereas with this mod, you will be able to induce over steer and correct. The nice thing about this mod is that for daily driving where you are not in a situation where you are trying to hammer through turns, the car will drive and behave just like stock utilizing the static 50/50 bias.

Anyway, my complete write-up is over at http://diffmod.plainbored.com.

Bottom line... now you can mod your one piece diff just like Poopie did with his two piece.

Here is the guy (not me) selling the washers over on VW Vortex as well (these are the ones I used):
http://forums.vwvortex.com/showthrea...tis&p=67969019

**biketsai** · 10-13-2010 06:45 PM

Awesome, keep us posted on how it handles!

**GetBoosted84** · 10-13-2010 07:00 PM

Definitely! I'll need to do some videos once I get some free time.

**Poopie** · 10-13-2010 07:47 PM

hah nice. got it all back together?

**Fink_tha_Audi** · 10-13-2010 10:39 PM

Hats off to you sir, for doing such a great write-up!!! It like a "4:1 Diff Mod For Dummies". Awesome!!!
Question tho I know you may not have tons of data on this but how reliable is this? How comparable is this to some of the pricey industry ones like from Stasis or JHM? Theoretically it should be the same, hopefully someone with one of those diffs can chime in.

**andyrew** · 10-13-2010 11:54 PM

Wonderful!! When mine gets back on the road this will be one of the first things it gets!!

**slowww328** · 10-14-2010 02:56 AM

Originally Posted by Fink_tha_Audi

Hats off to you sir, for doing such a great write-up!!! It like a "4:1 Diff Mod For Dummies". Awesome!!!
Question tho I know you may not have tons of data on this but how reliable is this? How comparable is this to some of the pricey industry ones like from Stasis or JHM? Theoretically it should be the same, hopefully someone with one of those diffs can chime in.

It's effectively the same modification. I'll have to look the quote up but when I was researching the mod initially (before I did it to my car) I stumbled across a post from one of the Stasis guys saying that all they do is change the washers.

**GetBoosted84** · 10-14-2010 06:12 AM

Originally Posted by Poopie

hah nice. got it all back together?

LoL, yep. I've been driving it for a little while now and so far so good.

Originally Posted by Fink_tha_Audi

Hats off to you sir, for doing such a great write-up!!! It like a "4:1 Diff Mod For Dummies". Awesome!!!
Question tho I know you may not have tons of data on this but how reliable is this? How comparable is this to some of the pricey industry ones like from Stasis or JHM? Theoretically it should be the same, hopefully someone with one of those diffs can chime in.

I'm going it's reliable :). So far it feels very solid and I don't have regrets. Couldn't give you an honest answer on how reliable it is... yet :). I'm only about 200 miles into using it so far.

**titikaka** · 10-14-2010 11:51 AM

is this mod for 01A trans. and if it is... how it looks like this mode, but for 01E for S4 6 speed?

**GetBoosted84** · 10-14-2010 01:00 PM

Originally Posted by titikaka

is this mod for 01A and if it is... how it looks like this mode, but for 01E for S4 6 speed?

I'm not sure what you're asking. What "mode" are you taking about?

**titikaka** · 10-14-2010 01:33 PM

hah sorry

i am talking about this "4:1 mode" writeup... for which trans is that writeup- 01A or 01E or both?! :)

:)

**Kyle H** · 10-14-2010 01:39 PM

His writeup is for 01A. I don't know if the 01E uses the same center diff, if it does, then the writeup will be the same.

**titikaka** · 10-14-2010 02:15 PM

thanks mate!! :) and nope, the 01A and 01E diffs are different!!

**GetBoosted84** · 10-14-2010 02:59 PM

Ahh gotcha. Yeah the torsen diffs are different between the 01A and 01E transmissions. However, the process is basically the same.

Here is a picture displaying the differences courtesy of JHM Motorsports:

**gmx** · 10-14-2010 04:15 PM

Sorry to jack but how much does a used fairly low mile center diff go for in the yards over there?

The 01As are unfortunately really weak. Mine is totally screwed. I need washers and a replacement hahah :)

**GetBoosted84** · 10-14-2010 04:17 PM

Originally Posted by gmx

Sorry to jack but how much does a used fairly low mile center diff go for in the yards over there?

The 01As are unfortunately really weak. Mine is totally screwed. I need washers and a replacement hahah :)

I have a real Stassis center diff available if you're interested. Shoot me a PM and we can chat.

**slowww328** · 10-14-2010 04:17 PM

The process would be the same (or very similar), it would just require making a different set of washers for the 01E diffs. There are actually two types of 01A diff, one piece and two piece, and they both use different types of washers.

Originally Posted by gmx

Sorry to jack but how much does a used fairly low mile center diff go for in the yards over there?

The 01As are unfortunately really weak. Mine is totally screwed. I need washers and a replacement hahah :)

I picked up an 01A 5 speed trans with the diff in it for $100 from force5auto in NH, so I'd imagine you can find them pretty cheap everywhere. If it's only the diff. you're after, you can pull it from anything 01A, so you could use an older car like an Audi 90, or even a 30v A4 trans w/ the longer gearing.

**b5a4gt28** · 10-14-2010 04:19 PM

Chris, Do work.

**GetBoosted84** · 10-15-2010 03:33 AM

You better be doing paintball tomorrow!

**titikaka** · 10-15-2010 10:13 AM

Originally Posted by slowww328

The process would be the same (or very similar), it would just require making a different set of washers for the 01E diffs....

ok , I understand that already , but where I can find the washers specs for 01E ...any suggestions??

:)

**[email protected]** · 10-15-2010 10:26 AM

This does NOT give you a static f/r 20/80 bias. Your static f/r bias is still 50/50. If this modification is done properly what it does is take a differential that could only send 2 times the torque of the other end of the car that is slipping up to 4 times the torque of the other end of the car that is slipping. This means driving around normally in a straight line the diff modification makes zero difference, even when taking a corner at a sensible speed it makes zero difference, only when one end of the car starts to lose traction does this modification do anything. If you understeer originally the differential could only send ~66% of the torque to the rear of the car if the rear is not slipping as well. Same goes for oversteer, a stock diff can only send ~66% of the torque to the front of the car if it is not slipping as well. If you did the modification properly with the proper materials (material type matters!) the diff can now send ~80% of the torque to either the front or rear if one end is slipping and the other isn't. This is why you will never noticed the differential modification until the limits of traction, though in a parking garage you may notice more binding and the rear inner tire scrubbing, normal. This modification does NOT give you a 40/60 static split like later model Audis.

Cheers,

**somebody5788** · 10-15-2010 10:39 AM

Originally Posted by Alex@Europrice

This does NOT give you a static f/r 20/80 bias. Your static f/r bias is still 50/50. If this modification is done properly what it does is take a differential that could only send 2 times the torque of the other end of the car that is slipping up to 4 times the torque of the other end of the car that is slipping. This means driving around normally in a straight line the diff modification makes zero difference, even when taking a corner at a sensible speed it makes zero difference, only when one end of the car starts to lose traction does this modification do anything. If you understeer originally the differential could only send ~66% of the torque to the rear of the car if the rear is not slipping as well. Same goes for oversteer, a stock diff can only send ~66% of the torque to the front of the car if it is not slipping as well. If you did the modification properly with the proper materials (material type matters!) the diff can now send ~80% of the torque to either the front or rear if one end is slipping and the other isn't. This is why you will never noticed the differential modification until the limits of traction, though in a parking garage you may notice more binding and the rear inner tire scrubbing, normal. This modification does NOT give you a 40/60 static split like later model Audis.

Cheers,

Thanks for posting this. I'm tired of correcting people hahaha

**[email protected]** · 10-15-2010 11:21 AM

I need to assign that write up to a hot key

**GetBoosted84** · 10-15-2010 03:27 PM

Originally Posted by Alex@Europrice

This does NOT give you a static f/r 20/80 bias. Your static f/r bias is still 50/50. If this modification is done properly what it does is take a differential that could only send 2 times the torque of the other end of the car that is slipping up to 4 times the torque of the other end of the car that is slipping. This means driving around normally in a straight line the diff modification makes zero difference, even when taking a corner at a sensible speed it makes zero difference, only when one end of the car starts to lose traction does this modification do anything. If you understeer originally the differential could only send ~66% of the torque to the rear of the car if the rear is not slipping as well. Same goes for oversteer, a stock diff can only send ~66% of the torque to the front of the car if it is not slipping as well. If you did the modification properly with the proper materials (material type matters!) the diff can now send ~80% of the torque to either the front or rear if one end is slipping and the other isn't. This is why you will never noticed the differential modification until the limits of traction, though in a parking garage you may notice more binding and the rear inner tire scrubbing, normal. This modification does NOT give you a 40/60 static split like later model Audis.

Cheers,

Alex makes a good point and is completely correct. When I posted this up, I was tired after writing up the DIY so I just threw together something real quick but I will correct my blurb at the top of this thread.

**titikaka** · 10-16-2010 04:41 AM

everything is ok with your writeup, but give us some specs on this washers... dimension ...washers material?

and what do you mean by this pic: you already replace 1 and 4 washers , so whats with the swapped 1 and 2 washers?

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**GetBoosted84** · 10-16-2010 04:56 AM

Originally Posted by titikaka

everything is ok with your writeup, but give us some specs on this washers... dimension ...washers material?

You need to PM slowww328 for the details on the washer since he is the one who did the leg work with getting the correct dimensions and washer material.

Originally Posted by titikaka

and what do you mean by this pic: you already replace 1 and 4 washers , so whats with the swapped 1 and 2 washers?

What I mean is that according to the diagram that torsen provides, there is a #2 washer at the bottom position in the stack as seen. However, Audi flipped the #1 and #2 position washers in their implementation of the torsen center gear set so when you are replacing the washer, you are really replacing the #1 washer even though it will be sitting in the position shown in the diagram where the #2 bottom washer is.

This is a photo of placing the replacement washer (#1) provided by slowww328 into position into the torsen:

**titikaka** · 10-16-2010 05:12 AM

so the old #2 washer stays at the bottom and the new #1 washer stays right above the #2 washer after replacement !? is that correct?

:)

**GetBoosted84** · 10-16-2010 05:17 AM

Originally Posted by titikaka

so the old #2 washer stays at the bottom and the new #1 washer stays right above the #2 washer after replacement !? is that correct?

:)

Nope, not quite... the #2 washer stays but it will be on top of the #1 washer in the stack. The nice thing is that it's very difficult to screw up since if you put the washers out of order and the beveled washer is not in the right place, the stack won't slide in.