STaSIS diff

[Billman]

Keep us updated JP

[JP]

OK a little update, as some may be aware from a recent post my gearbox decided to decommission 2nd. So I decided for ease to source another box. Rather interestingly I came across a Diesel Box with the same 4.111 final drive and upon investigating the rest of the ratio's more carefully found that it has identical 1st, 2nd and 3rd to the earlier 5 speed box and slightly longer 4th and 5th whereas 6th is a ridiculous motorway cruiser 2240rpm to do 70mph :-). So I figured I'd give it a go as I'd have improved 1/4 mile coupled with improved motorway economy on those longhaul journeys now the petrol prices are getting silly.

Putting that aside I figured as the box was being swapped and it was going to be on the floor and have a fresh oil change this was the perfect time to fit the prototype diff for a bit of testing. So I modified the one on the box as they are individually shimmed to each box so not easily interchangeable without reshimming and went to pick the car up tonight. The fact the roads were wet and the boot of the car was full up with bits meant that the extra camber on the back along with the damp conditions weren't ideal for testing on the way home. However so far I can definitely say the following things:-

- The torsen diff is operating smoothly and quietly under load, cruising and coast down.

- It appears to have a better feel in and out of corners, however I cannot be 100% on this as been driving a FWD Diesel A4 Avant for the last 3 days.

Once I've emptied the boot out and the roads are a little drier I will give the car a proper run round the local lanes as they're all national speed limit so they are a good testing ground as there rarely is a car on them during the day let alone at night. After which I'll report back.
The second half of the test will be carried out by Doug who is going to be fitting the other diff to his new widebody creation however he is going to try and utilise his dyno to see if we can measure a physical change of state by first running it with the stock Torsen and then the modified one.

JP

[JP]

Need to go and buy some roll clips the right length to lock the diff casing together and get it back to Doug. Then it's upto him how quick things progress from there. With their current workload probably not that fast :-)

[Jamo]

Working hand in hand with Doug, he provides resources, testing and existing know how in exchange for the end product. The more we look into it though the less it becomes a DIY thing or a quick job, almost to the extend that the other week I was about to just swallow the cost and order a stasis one. As all the info floating about the net is misleading and doesn't give the correct end results. So ended up starting from scratch to work it out which is painfully time consuming. Truth be told if what has been changed works then I wouldn't know where to begin with writing instructions to the extend that the currently modded diff for testing (if it works) is being kept as a template for the future.

How did this progress?

[mouse]

There's a sale / group buy on JHM's version of this here: http://www.euroaddiction.net/forum/s...8732#post58732
Although they only refer to B5 diffs onwards (is the S2 diff same as B5 ?)

Also in regard to the T1 type torsen they state:

"If you have a T1 we can only modify half of the diff due to its older design so you will not get a full 4:1 diff, it will be somewhere in between a 2:1 and 4:1."

[JP]

Working hand in hand with Doug, he provides resources, testing and existing know how in exchange for the end product. The more we look into it though the less it becomes a DIY thing or a quick job, almost to the extend that the other week I was about to just swallow the cost and order a stasis one. As all the info floating about the net is misleading and doesn't give the correct end results. So ended up starting from scratch to work it out which is painfully time consuming. Truth be told if what has been changed works then I wouldn't know where to begin with writing instructions to the extend that the currently modded diff for testing (if it works) is being kept as a template for the future.

[Jamo]

Are so your doing it JP, MRC mentioned it on audisrs they were researching it

i'm watching with interest as I had planned to do this mod very shortly

[Error404]

good to have some knowledgeable input into this
Interested to see the results

[JP]

OK a little update for those that have been watching this thread.

1st of all to fit new bearings to the diffs is definitely never going to be a universal washer bearing set they are going to have to be individually machined up. As I have had 3 x 01E torsons in my hands now and they are all different on the bearings and thrush washer sizes depending on the casting they have been placed in.

Now having sat down with a gearbox specialist that regularly deals with these types of diffs and looking at the original bearing construction and the needle roller bearing upgrade we have come to the conclusion it is not a very good mod.

This is because

1) The torque bias from front to rear can only be changed by such methods as altering the tooth count.

2) By fitting needle roller bearings and reducing the frictional co-efficient you are in effect getting rid of the LSD style properties and changing the Torson into an open diff. Hence the more FWD effect under braking and more RWD effect under acceleration. You have effectively almost turned your motor into a 2WD car that chooses to swap depending how the load is applied. Admittedly it will make for entertaining driving but it goes against everything of why I wanted a Quattro.

3) I've had the pleasure of having a Stasis diff in my hands to strip and inspect and can confirm that there is no needle roller bearings in them. I have looked at it very carefully and I believe I know the changes that have been made to make them what they are.

I've prepped a stock Torson to what I believe the Stasis spec is and will be doing some tests with Doug at MRC on an S4 as they are much easier to swap round on the later box's. If it works out then it becomes do able although time consuming and tedious. If I'm wrong on my assumptions it will disintegrate the test diff into lots of little pieces as we load it up

[JP]

^^^^Nope.

Just trying to work it all out at the moment. The pics I've seen are of a diff of a 01A box. The one I have in my hands came of an audi s4. Hence the visual difference.

I know by changing the friction coefficient of the bearings themselves you apply more or less torque loading. The bit I'm trying to work out is how much effect there is by shifting the gears back and forth in relationship to the meshing friction of the external roller gears as this has an effect aswell. Or whether it is mandatory these distances stay the same to ensure good gear wear and all we are doing is changing the friction co efficient between the thrust washers and bearings. In which case we can utilise the original thrust washers and grind them down to suit ensuring the gears stay located correctly.

As it is also 100% mandatory that the gears are correctly timed on re assembly otherwise horrors will occur further leading to my suspicions that it is down to the bearing alone.

[Rusty]

Can you not create a bush that can be adjusted for width, perhaps with a fine thread adjustment or internal shims? Just a thought.

[JP]

Just discovered that the Torsen diff I got in my hands is a different design hence the inaccuracy in the bush measurements. Will have to seek out another diff to try it out on.

[JP]

OK I've sat down and looked at this thread. I've got a torsen diff in pieces in front of me and the measurements that are provided for the washers don't add up. Basically come short by almost 6mm.

My local bearing place has the bearings and shims in stock I got a magnetic baseplate surface grinder and I can turn the bushes on the lathe. I've also got a supplier round the corner for the roll pins for re-assembly time wise to shim them up and grind is a good few hours of work. So I'm starting to understand the prices that are being charged as it's not a straight forward make a universal set of shims up it has to be custom machined to each individual diff. Which means lots of setting up time involved including assembling it, measuring, disassembling, setup and machine again, re assemble measure etc... you get the picture.

It's done easily enough but tedious none the less. Not as expensive as 034 are charging but not as cheap as a couple of bushes either. I'm going to have to do some more maths to work out the frictional co-efficients relative to the offsets. Once I've got a solid result on paper I'll knock one together and try it out.

[Error404]

I've been too busy to do anything further with it TBH, its on my list of stuff to do but unlikely to get anything done for a few months at least as i have bigger fish to fry right now

[goodall]

Any more luck on getting a group buy sorted out?

Was looking at the fsae section torsen website seems if have a spare torsen diff can just use the thrust washers out of it.

Also not discussed but, rather having the, steel washer-brass washer-steel washer, in the middle could not just have a thicker brass washer to increase the friction there some more aswell
and even use brass instead steel to replace the roller bearings to increase tbr even more
i'm assuming brass high coefficient of friction...