Torsen V8 rear diff swap! How-to.

[mcandmar]

Its surprising how many people who have done the torsen conversion never mentioned that, kind of worrying as it was immediately obvious to me the S2 flanges were shorter.

Did you have to set the bearing preload when installing the diff, i'm going to have to for mine as its ever so slightly tighter, frustrating as its such a PITA to get the diff/crown wheel in/out of the casing.

[porkkis]

I'd say mine is slightly less tight than before. I can feel a slight backlash when turning the pinion. I did check the contact using colour paste and I think it's fine.

I might change the bearings and adjust the ring/pinion some day but not now.

[goodall]

Porkkis, did you measure how much spline engagement is left when adding the spacer? I had been planning to get S2 shafts for using with the V8 cups but I have a spare 90 stub

As for blocking off the old difflock mechanism port, I used a 35mm core plug (frezze plug, call what you will)

[mcandmar]

V8 Torsen Seals

I had to source some seals to fit a torsen into an Avant housing as Audi claim they are all NLA.

All seals are made by Corteco, same as OE. I sourced mine from http://abbeyseals.ie/

Right side seal for diff, also input shaft and gearbox outputs,

016409399B : BASLDRWx67 : 45x60x8 : €5

Left side seal for manual locking diff,

017525400A : ? : 72x122x10/13 : €20

Left side seal for torsen diff,

017525400C : BASLSFRSX7 : 45x122x12/23 : €56

As above you need the torsen diff, both V8 output flanges (NLA) and the two securing bolts. The most difficult/annoying part of the conversion is the fact the crown wheel is slightly wider than the hole in the diff casing so it wont lift straight out. Instead you have the tedious task of separating the crown wheel from the diff inside the case in order to get them in/out. If you want to measure the bearing preload and teeth mesh then you have to do all that half a dozen times. I also removed the lever for the manual diff lock and pluged up the rubber boot, but there is no reason why you cant leave it in there. Also the original output flange from the diff lock side has a metal dust guard pressed on which can be transferred over to the V8 flange.

As for difference its too early to say as its only been in a couple of days. The one thing i have noticed is 90 degree turns, for example if your stationary waiting to turn into a side street and go for a gap in the traffic, not full throttle, just 2/3rds using .5-1bar boost i can feel something going on back there. With the open diff that would be no where near the point of spinning wheels, it would have just driven off without drama. With the torsen i can feel the back axle tighten up and start to scrub tyres and push the tail like a RWD. Not sure if i like it or not, but i have the horrible feeling its going to chew through rear tyres a lot quicker now.

More seat time needed

[Error404]

Good info on the seals Mark
The avant diff must have a different sized cover on the casing as there are no issues lifting the diff carrier & crown wheel assembly out on the coupe.

I have actually found no difference in tyre wear with the rear torsen, mines been fitted a few years now. Like a normal LSD in a RWD car when you start to press on you really notice the difference in how the car behaves, I think you will like it
I am looking forward to trying it in combination with the 40/60 split T3 centre diff in my coupe

[andy10v]

Good info on the seals there, thanks

The most difficult/annoying part of the conversion is the fact the crown wheel is slightly wider than the hole in the diff casing so it wont lift straight out. Instead you have the tedious task of separating the crown wheel from the diff inside the case in order to get them in/out. If you want to measure the bearing preload and teeth mesh then you have to do all that half a dozen times.

That must have been a PITA, how did you separate and refit in situ? Refit by using longer bolts to pull it on?

[mcandmar]

Good info on the seals there, thanks

That must have been a PITA, how did you separate and refit in situ? Refit by using longer bolts to pull it on?

I used a block of wood in the diff lock side so there was some clearance between the crown wheel and pinion with the diff resting on its side. Then a combination of tapping the bolts with a hammer and using a lump of brass to hammer around the outer ring to work it off. To get it on i used four long bolts to get it started until i could thread the main bolts in.

[irishs2]

Good info on the seals Mark
The avant diff must have a different sized cover on the casing as there are no issues lifting the diff carrier & crown wheel assembly out on the coupe.

I am slightly confused, i had no difficulty getting my diff carrier out either, is the v8 crown slightly larger ?

[mcandmar]

Really, hmm. It wasn't just me i had my father look at it and he wiggled it about, swore at it, and came to the same conclusion that it dosent fit through the hole. You have to use the original ring gear as the V8 one is slightly thicker, which is fine as i would prefer to treat the ring gear and pinion as a set.

[irishs2]

Cool, no loss of time really so as you had to remove the ring gear anyway, and there was no problem fitting the rear drive shafts to the v8 flanges?

Its something I would like to do, but its way down on my list .. my very long list.

[mcandmar]

Yup bolts right up, no hacking, grinding or bodgery needed so can easily be put back to stock. Its one of those things that was never a priority, and i probably would never have done. Only reason i removed the original diff was because it was leaking oil so bad. David kindly lent me a diff so i could remove and rebuild mine. Then figured while i had it apart why not give the torsen a go, something i bought and squirreled away many years ago

[mouse]

I had to source some seals to fit a torsen into an Avant housing as Audi claim they are all NLA.

All seals are made by Corteco, same as OE. I sourced mine from http://abbeyseals.ie/

Right side seal for diff, also input shaft and gearbox outputs,

016409399B : BASLDRWx67 : 45x60x8 : €5

Left side seal for manual locking diff,

017525400A : BASLSFRSX7 : 72x122x10/13 : €20

Left side seal for torsen diff,

017525400C : BASLSFRSX7 : 45x122x12/23 : €56

As above you need the torsen diff, both V8 output flanges (NLA) and the two securing bolts......

Thanks for the info on the seals.
Do the two securing bolts (i assume you mean the output flange securing bols) need to be from the V8 diff or can the S2 bolts be used?

[mcandmar]

They need to be from the v8 as the heads on them are different, on the S2 the flanges have a counter sunk hole in them so the bolt has a 45 degree taper. Where as on the V8 there is a flat mating surface and uses a regular hex head on the bolt.

[mouse]

B ugger.... I thought all I needed now was the left side torsen seal but I need to find some bolts now too.

[mcandmar]

N0104211, M8x98, 2 quid each in the catalog so wont break the piggy bank