STaSIS diff

[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

[Billman]

Keep us updated JP

[Kliminati456]

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

RWD19T any feedback on this mod and if it is worthwhile?

[JP]

Sorry for delay been a bit busy lately to write up a proper report. I still want to do a back to back test on the dyno so by looking at the raw data we should be able to determine the exact change in power distribution.

there are several things that I have noted so far which indicates that the modification has worked, although until I have dyno figures to correlate what my butt dyno is telling me I don't wish to commit to it.

1 - When it was Icy mid month last month and I accelerated hard in 2nd gear the back of the car kicked out violently, previously the whole car used to sidestep.

2 - Going round a large roundabout in the dry, my tires used to star squealing at around 45mph and the car would start to understeer if I stayed on the throttle, now I can go round the roundabout at the national speed limit of 60mph with no squealing tires and carry on feeding the throttle out of the corner with what feels like no understeer, instead possibly a tiny bit of oversteer as if I had more camber on the rear suspension setup.

3 - There is steep hill near my house where at the bottom there is a bumpy roadsurface at the T-junction. Before driving the 30mph speed limit and coming to a hold at this junction when heading down the hill I used to ever so slightly get the ABS to kick in as I hit the uneven roadsurface. Since having changed the spec of the diff the car no longer applies the ABS under the same conditions. No change in brakes or brake fluid or anything other than the diff has been changed to achieve this.

Which prompted me to try the final test:-

4 - Driving the local lanes with the diff mod, I am able to brake later into corners whilst driving the 60mph national speed limit. Similar to the braking situation in no.3 the car feels less unsettled when braking hard going into corners compared to before when it used to oversteer and plough the nose down. The nose still goes down but there doesn't seem to be the same oversteer going into the corner under heavy braking allowing me to start feeding the throttle again sooner.

My butt dyno tells me that the car feels more positive in cornering response under acceleration. It's not tail happy as my old V8 Capri nor is it understeer galore as found on a FWD motor. There appears to be just that little bit extra to allow me to feed the throttle in nicely whilst cornering for a rapid exit without being tail happy like a beemer, or starting to drift towards the hedges as it used to do unless you fought with the steering.

Such a pleasure it has been to drive that it has now prompted me to finally upgrade my brakes from stock as for the first time ever I managed to get brake fade in this car

I'm going to be converting another diff in the next 7 or so days on my friends quattro'd passat to get his feedback too.
What we'll try and do is run his car up on the dyno before changing it over so we can also see the actual power distribution. Just to make sure I'm not imagining things. But as it stands I think we cracked it

JP

[Dan]

Nice, sounds like a worthwhile upgrade.

[jogi730]

Hey JP,
Sounds like you might be inundated with work soon if it works.
Good work matey!

[Error404]

are you sure the dyno will tell you anything JP? The static bais would not have changed - still 50/50?

[Mcstiff]

I'm interested!

[Jeffer]

nice research! keep us updated pls

[JP]

are you sure the dyno will tell you anything JP? The static bais would not have changed - still 50/50?

I'm hoping because it is a brake dyno with coast down for rolling losses it will show a difference in the raw data. As we can load it up the same way as you would accelerate on the road. However knowing the way the friend in question drives his car I would be happy to go on the strength of his confirmation if the dyno doesn't show anything. As he will definitely notice the change.

[S2central.net]

THIS is very interesting... I must catch up on thise whole thread but post #94 really caught my eye.

[Billman]

anything new on this?

Does anyone ever used these shims and can report about the results?

What does stassis change in the diffs at the end of the day?

[andy10v]

Scott at Advanced Automotion is doing a special on this;

http://www.audizine.com/forum/showth...275.00-shipped!

AAM 01E high bias center diff.. $275.00 shipped!

We've been installing high bias diffs in our gearboxes for a little over 2 years now and want to offer this product to the 'Zine as a standalone offering. For those not familiar with what a high bias center diff does is it widens the torque proportioning ratio from front to rear, allowing the vehicle (under conditions) to behave more like a rear wheel drive car. What we do to these isn't merely "Shim Slapping" but rather an entire differential overhaul.

The internal gears are cryo treated for the utmost in strength, and shim selections are carefully chosen to eliminate any possible gear stack movement which can cause clunking under tight turns. If the needel bearings require replacement they are replaced.

This is followed by a 1 year warranty on the entire diff, not just the parts we replace. This isn't on our website yet so contact me if you want to take advantage of this. We do have cores (and a $300 core charge) or to avoid the core charge, you can send me your diff. If there is accelerated wear on the gears your core may not be acceptable, if you have any questions contact me.

Dunno what shipping would be like.

[Billman]

so this is just shims (appart from the cryo part).

[quattro84]

And the play between parts. I think it's crucial for the bias.