Crown Gear Equipped? Opinions?

[walky_talky20]

Hey, first I wanted to send out huge props to walky and other contributors here. The type of analytical discussion we have here is reminiscent of the old Quattro List/Audifans group, which was likely the first such group for Audi owners online in the infancy of the internet. The discussions were via email distribution and highly analytical and technical, with numerous engineers and hands on people. Some even started their own Audi parts businesses from the knowledge and connections they gained from there. Even if we don't end up with a consensus or we are wrong, the analytical nature of the talks and walky's input has opened up an insightful dialog that is informative and even entertaining. It was because of the Q-List that I began wrenching on my own cars and rebuilding and restoring them.

So for my example: German 2011 A4 Avant, 2.0 tfsi S-tronic Quattro, MSA transmission code. I have the outdrive associated with the crown gear. I also hunted around online for used transmissions and they all have the same output shaft. I can't imagine that I have one, but my particular car has lots of mystery combinations on it that even the Audi dealer is having trouble with (even little things like my oil pan drain bolt). The 1LJ brakes I might have an explanation for, though ;) This is also one of the early transmissions that had defective drive range sensors, which were replaced under warranty.

I actually doubt I would feel any difference, though the 40/60 split of the standard center differential is noticeable on the uncontrolled sections of the German highways when rounding turns.

Here's what it looks like on our equivalent of Craigslist (which is operated by Ebay): https://www.ebay-kleinanzeigen.de/s-...18073-223-4408

and another: https://www.ebay.de/itm/Audi-Getrieb...-/272911356881

You are very kind. Thank you for sharing as well!

From what I see in the parts diagrams, it's hard to tell for sure what a 2011 A4 DSG car would have. The diagram looks like a crown gear, but the part number ends in "H" (like most torsens) instead of "K" or "L" (like most crown gears). Also the part description says torsen (but it says this for known crown gears as well - probably an expected error when they ran solely torsen center diffs for 25 years). I can't say for certain, but I'm pretty sure it would be a torsen.

[Riccird1]

Very interesting finds!

To add to this discussion I browsed up the 2013 A6 which has 2 transmission options for quattro equipped cars - one S-tronic box and one tiptronic box.

The tiptronic is a ZF box used in the high torque applications of the 3.0 bi-tdi engine and RS6 (and possibly S6 too).

S-tronic in the rest of them.

The diff on the A4 tiptronic and the A6 tiptronic is by pictures the same, although I believe the box itself is not the same since the bi-tdi and RS6 can run insane amounts of torque.


Do you think they find the crown gears to be a design not fit for high torque applications since they won't equip the tiptronic boxes with them?

The RS5 only makes 430nm of torque (317 lb ft) which could be considered a low torque application.

If the ZF boxes are rated for X amount of torque, maybe they're required to make sure the differential can handle this amount of torque too?

I don't see any engineering difficulties in installing the crown gear diff on a ZF box physically..


Edit: My 2013 (b8.5) A4 with a manual gearbox has the crown gear type btw

[SixtyFortyDiff]

Just found my way back here (I should probably figure out how subscribing to threads works, after being a member for 10 years, eh? lol).

That's an interesting point about the axial forces and I can see how that would effectively provide a locking effect before wheel slip. Basically the gears are cut so they try to "walk" away from each other a bit, and this ends up putting pressure between the output gears and the housing. Thus locking the axles together progressively. (Time to watch the Crown Gear video *again* with this in mind). The only problem is that is it's using friction within the "plate packs" to transfer the torque. And the plates will necessarily be slipping when torque is transmitted and any amount of RPM difference exists between the front and rear axles. Like putting your foot down when turning...which happens a lot.

I suppose it is probably designed to just walk a little further as the plates get thinner - so wear does not immediately affect the locking ability. And the material is probably fairly awesome so it doesn't wear too fast. But it should be noted that friction material is necessarily going to end up in the gear oil. And that stuff should probably be changed more often as a result. I'm sure Audi still says the gear lube is lifetime.

This does beg the question if some aftermarket outfit will take one of these things apart and swap the "plate packs" to something with more aggressive friction properties. Like they did with the Torsen washers. Crown Gear Plate Pack Upgrades, we might call them. +40% torque transfer capability! +20% over OEM RS5 Crown Gear! I guess time will tell.

Exactly - as the gears try to 'walk' away from each other, a locking force is generated that is proportional to the torque input to the diff. Functionally, it seems they could have just gone with a 1/1.5 way ramp/clutch style LSD, but maybe that would have caused patent issues.

While it's true that the plates utilize friction to limit differentiation in the crown gear diff, keep in mind that this is also the case with a Torsen T3 - friction between the gears and the housing, as well as friction between clutch plates, is what limits differentiation in a Torsen (search Google images of Audi's "self locking center differential" - clutch packs are used in the Torsen as well). Difference being that in the T3 if one axle loses resistance entirely, the gears essentially have nothing to "push against" to generate a locking force, whereas I think the advantage of the crown gear diff is that it will generate a locking force as the gears walk away from each other regardless of axle grip, similarly to a clutch style LSD.

I think you're probably right about the gears being designed such that they still generate sufficient lockup force as the clutch plates wear, and we'd both probably be surprised at how little wear occurs even under hard driving. Wear is a function of clutch pack load and speed difference, and it's rare that both values are high simultaneously (ex. - heavy throttle input is usually done in straights or sweeping turns where axle differentiation is none/minimal; high axle differentiation occurs with large steering inputs, like parking lot maneuvers, where torque input to the diff will be minimal; I'd think most wear would occur in tight corners on a track, or doing donuts at full steering lock, with full throttle...lol... but even then, the wheels are likely to break loose, at least somewhat, which removes load from the diff clutch packs).

While I'm not sure exactly how the center diff is lubricated/cooled, I agree on changing trans fluid periodically regardless of what Audi states! (I'm probably gonna change my B8 S4 6MT oil between 100-150k)

[cybernet99]

OK, I just looked at my transmission code, I'm running a 2010 6MT B8 A4 with code LLT. Will have to try to get my phone under the car tomorrow after work.

I came across this thread searching for anyone that might know if we have the ability to change our diff gear ratios? I think factory is 3.68 … I want to bump it a bit to 4.10 for better acceleration, and instead of the "sport diff" with all of the electronics and sensors, what about just a good old locking diff for the rear? It started with someone talking to me about the JHM 4:1 centre diff, … that got me going thinking about other mods.

Great write up and investigation @walky_talky20

[walky_talky20]

Thanks. I'm glad you found it interesting.

As for changing the rear diff ratios, I have actually done that on my B5. All of the 5-speed MT B5 A4's have 3.89 final drive, but mine has 4.11's. The key when changing the rear end ratio is that you also much change the *front* to match. Otherwise you will wreck the center differential pretty quick. It will move down the road ok, but it won't last long. If it's a torsen you will heat up the worm gears and wear out the friction washers. If it's a crown gear you're going to wear out the "plate packs". Best case, things wear out and you progressively lose the Torsen TBR (torque bias ratio - the ability for the diff to do it's magical torsen stuff) or you lose the "locking torque" ability of a Crown Gear. Worst case things get too hot and it starts spitting chunks of metal into your gear oil.

The way I was able to change my ratio from the correct 3.89 to 4.11 was to obtain an older Audi gearbox. The early (~1988-1991) 5-speed torsen quattro gearboxes (01A) were 4.11 final drive. In ~1992 they changed to 3.89 and pretty much stayed that way until their discontinuation around 2005 . So by sourcing an early version of the trans, that gave me the front diff at 4.11. Then I could pair it with an automatic B5 rear diff, which happens to also be 4.11. This is what makes time travel possible. To reproduce this on a B8, you have to see what is available among the possible transmissions that will bolt to both your engine & your chassis. You can't really go older because you need something with the magic MLP design to fit (front axles emerging in front of the flywheel, who would have thought!).

[Kolbenringe]

Bringing back this very interesting topic. Youtube started showing me DSG teardown videos in my feed, so I want to post at least a couple here. I watched three and I'm pretty confident that I could rebuild my transmission if needed.

This first one appears to be from an Audi service center in Russia (or Bulgaria). The quality of the video makes the language differences irrelevant, with the exception that they got the article for "Service" wrong. It's not
DAS Audi Service, it's DER Audi Service. After 11, they tear into the tail section with the center differential.



This one is from Elring, the gasket and chemical company. Also very good. No words. Around 7:40 they start the tail section.



I would save the videos for future reference, if I were you guys. There are others out there dealing with the Mechatronic and also specific to clutch replacement.

[Audi 4 Life]

Thanks. I'm glad you found it interesting.

As for changing the rear diff ratios, I have actually done that on my B5. All of the 5-speed MT B5 A4's have 3.89 final drive, but mine has 4.11's. The key when changing the rear end ratio is that you also much change the *front* to match. Otherwise you will wreck the center differential pretty quick. It will move down the road ok, but it won't last long. If it's a torsen you will heat up the worm gears and wear out the friction washers. If it's a crown gear you're going to wear out the "plate packs". Best case, things wear out and you progressively lose the Torsen TBR (torque bias ratio - the ability for the diff to do it's magical torsen stuff) or you lose the "locking torque" ability of a Crown Gear. Worst case things get too hot and it starts spitting chunks of metal into your gear oil.

The way I was able to change my ratio from the correct 3.89 to 4.11 was to obtain an older Audi gearbox. The early (~1988-1991) 5-speed torsen quattro gearboxes (01A) were 4.11 final drive. In ~1992 they changed to 3.89 and pretty much stayed that way until their discontinuation around 2005 . So by sourcing an early version of the trans, that gave me the front diff at 4.11. Then I could pair it with an automatic B5 rear diff, which happens to also be 4.11. This is what makes time travel possible. To reproduce this on a B8, you have to see what is available among the possible transmissions that will bolt to both your engine & your chassis. You can't really go older because you need something with the magic MLP design to fit (front axles emerging in front of the flywheel, who would have thought!).

Thanks for the info bro! I ended up switching from early production torsen to late model crown diff on the 6MT. I was originally going to modify the 0B1 with the STASIS diff mod but ended up going with crown diff cant wait to see how it feels.

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[SixtyFortyDiff]

Thanks for the info bro! I ended up switching from early production torsen to late model crown diff on the 6MT. I was originally going to modify the 0B1 with the STASIS diff mod but ended up going with crown diff cant wait to see how it feels.

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More info on how you switched from Torsen to Crown Gear Diff? Did you just swap in a later model 6MT, and if so, how'd you verify the type of center diff?

[Audi 4 Life]

More info on how you switched from Torsen to Crown Gear Diff? Did you just swap in a later model 6MT, and if so, how'd you verify the type of center diff?

Swapped from 6AT to 6MT got my parts from a 12 A4 6MT. I got all the parts form the same car so no confusion matching rear diff to transmission.

If you want a list of necessary parts for the swap shoot me a pm

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[SixtyFortyDiff]

Swapped from 6AT to 6MT got my parts from a 12 A4 6MT. I got all the parts form the same car so no confusion matching rear diff to transmission.

If you want a list of necessary parts for the swap shoot me a pm

Sent from my SM-G960U using Tapatalk

Thanks for the offer. My S4 was a manual anyways, but regardless I sold it and got a Golf R so not relevant for me anymore.

I assume you didn't open up the rear case and take a look at the center diff when you did the swap? It would be kind of cool for somebody to verify that certain year A/S4's got the crown gear diff!

[MarkusS4]

What an interesting read!

So i was able to jump on the group buy of Jay's LSD front differential earlier this year. in doing so, i had to remove my transmission from my 2010 audi s4 (built in September of 09). it had a torsen center diff 0B4 409 751 H and my transmission code is KMR (6 speed manual). Jay had a 2010 s4 transmission laying around from his LSD testing. The transmission code was LPE and it had the crown gear diff 0B2 409 755 K.

I assembled the 0B2 409 755 K crown gear diff into my transmission and everything bolted up just fine and spun correctly. I checked all of the other part numbers such as the center diff cover and the center diff retaining plate, and they are all the same. the only difference is the center diff itself.

so my question is, can i use the 0B2 409 755 K crown gear in my torsen transmission?

Thanks!

[Smac770]

The only part number that Audi seems to clearly indicate as using the crown gear center diff design is the 0B5 409 755 J in the B8 RS4 and RS5. 0B2 had 755A -> 755H and then 755J -> 755K -> 755L, but no reason to believe the second line was crown gear and not just a compact repackage of the parallel axis T-3 design.

[MarkusS4]

If audi was trying to make something "more compact" then they failed terribly. My 0B4 409 751 H is the same size as the 0B2 409 755 K.

[Smac770]

Post a pic of it/them. Finding pics of specific part numbers is not particularly easy.

[Audi 4 Life]

What an interesting read!

So i was able to jump on the group buy of Jay's LSD front differential earlier this year. in doing so, i had to remove my transmission from my 2010 audi s4 (built in September of 09). it had a torsen center diff 0B4 409 751 H and my transmission code is KMR (6 speed manual). Jay had a 2010 s4 transmission laying around from his LSD testing. The transmission code was LPE and it had the crown gear diff 0B2 409 755 K.

I assembled the 0B2 409 755 K crown gear diff into my transmission and everything bolted up just fine and spun correctly. I checked all of the other part numbers such as the center diff cover and the center diff retaining plate, and they are all the same. the only difference is the center diff itself.

so my question is, can i use the 0B2 409 755 K crown gear in my torsen transmission?

Thanks!

pretty sure at the least the driveshaft needs swapped cuz the connection is different iirc.

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[MarkusS4]

Post a pic of it/them. Finding pics of specific part numbers is not particularly easy.

Torsen vs Crown.jpgCrown Part number.jpgTorsen part number.jpg
Forgive me as i am new to using Audizine. The 755 K (on the left) is slighly smaller but only marginally. I will have to say that the 755 K (on the left) is lighter as well. How can i tell if it is crown or torsen?

[MarkusS4]

pretty sure at the least the driveshaft needs swapped cuz the connection is different iirc.

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The shaft for the flange (torsen) and the shaft for the stub (crown maybe) are the same. i just put the 755 K in place of my 751 H and it seemed to work well. i just dont know how to verify that.

[Audi 4 Life]

The shaft for the flange (torsen) and the shaft for the stub (crown maybe) are the same. i just put the 755 K in place of my 751 H and it seemed to work well. i just dont know how to verify that.

Maybe I'm miss understanding what your saying. But when I swapped from auto to manual the the connection for the shaft to the center diff was different between crown and torsen manual trans.

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[Smac770]

KMR and LPE are both 0B4 6-speed manuals with 31/9 ratio. The LPE used the spline shaft instead of the flanged shaft and so I suspect Jay's transmission is from a 2011, not a 2010 (ie, likely a 2010 build date, but not a 2010 model year vehicle).

KMR transfer case:
https://audi.7zap.com/en/usa/audi+a4.../4/409-409085/

LPE transfer case:
https://audi.7zap.com/en/usa/audi+a4.../4/409-409087/

So we see the component line is slightly different.

part	KMR	LPE
transmission output shaft	0B4 311 201	0B4 311 201 B
bearing bush	01E 311 807	0B4 409 073
spacer sleeve	0B4 311 230 A	n/a
compensation washer	WHT 002 286 (x)	n/a
grooved ball bearing	0B4 409 769 A	n/a
center differential	0B4 409 751 H (now 0B2 409 755 H)	0B2 409 755 K (now 0B2 409 755 L)
pressure spring	01E 409 881	0B5 409 881
grooved ball bearing	0B2 409 775	n/a
compensation washer	01A 311 393 (x)	n/a
belleville spring	01E 409 791	n/a
securing ring	n/a	N91 029 701
securing ring	N 0 123 761
grooved ball bearing	01E 311 235
housing	0B4 301 213 B	0B4 301 213 E
balance weight	02X 301 307 A	0B4 301 307 A
radial shaft seal	0B2 409 400
protective ring	n/a	0B4 409 375
transfer case output shaft	0B4 409 809 C	0B4 409 809 H

If you can account for the reasons of the part differences, then it should be possible to create the right combination to work effectively.

[Smac770]

So here's my report.

Slide1.JPG

Slide2.JPG

Slide3.JPG

Slide4.JPG

Slide5.JPG

Slide6.JPG

Slide7.JPG

Slide8.JPG

Slide9.JPG

Slide10.JPG

[walky_talky20]

Smac770 coming in here and dropping the weapons-grade center diff information.

You sir, are a gentleman and a scholar. I am honored to be proven so wrong, and in so much detail. I tip my hat. My original post now looks like kindergarten crayon scribbles by comparison.

[Audi 4 Life]

Wow, x2... damn mac very impressive.

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[Audi 4 Life]

Since this thread has so much info i supppsed i should contribute a little something. I know theirs not many manual B8's out there but theirs an auction on eBay with stasis torsen diff shims for early B8 manuals only and some other models as well if anyone's looking to upgrade their diff to 4:1

https://www.ebay.com/itm/173598411464


Not affiliated but its a great mod and uber good deal for quality shims.

[MarkusS4]

So based off this information, the 0B2 409 755 k out of an LPE transmission is still a torsen and not a crown? I dont fully understand that. The 0B2 409 755 k is the same part number as the Crown diff out of a 2013 DSG which Audi says has the crown diff.
2013 S4 DSG.PNG

Also i have found several 2010 S4s with the LPE transmission in it.
2010 S4 LPE.jpg

[Smac770]

"which Audi says has the crown diff", when did Audi say that? Do you have pictures of a dismantled 0B2 409 755 K to document the crown gear internals? E.g., SSP 478 for the 2011 A7 says "Crown-gear limited slip differential" on the drivetrain overview, page 29, but then shows an obviously not crown gear diff when it gets to the detail pages.

Spline shaft on a few MY10; wouldn't shock me. What were the actual build dates of those vehicles? The transition date for the cardan shaft on the 6-speed + 3.0T is listed as Mar 8, '10. And are you going by the VIN on the vehicle or numbers on detached pieces of paper?

[MarkusS4]

"which Audi says has the crown diff", when did Audi say that? Do you have pictures of a dismantled 0B2 409 755 K to document the crown gear internals? E.g., SSP 478 for the 2011 A7 says "Crown-gear limited slip differential" on the drivetrain overview, page 29, but then shows an obviously not crown gear diff when it gets to the detail pages.

Spline shaft on a few MY10; wouldn't shock me. What were the actual build dates of those vehicles? The transition date for the cardan shaft on the 6-speed + 3.0T is listed as Mar 8, '10. And are you going by the VIN on the vehicle or numbers on detached pieces of paper?

So i was unable to find the lineup changes for the S4 (i did some other time but didnt save where i found it) but this link will take you to the A5/S5/RS5 Linup changes for 2013. Both the RS5 and the S5 now had the crown-gear in the S tronic models. This "crown gear" is the same part number as the center diff in the LPE manual transmission. Its on page 21.

https://www.audiworld.com/model/s5/1..._MediaInfo.pdf

When exactly the spline shaft vs the flange shaft transition started is actually pretty irrelevant. All im saying is the LPE has a Crow diff in it and due to the crown diff, they had to make a spline output shaft. AND this transition happened sometime in 2010 meaning the S4 LPE transmission also debuted the crown diff along side of the RS5.

ALSO: Audi claims that the Crown center diff is roughly 4.41 pounds lighter than the torsen diff. I weighed both center diffs from the KMR transmission and the LPE transmission and the LPE center diff IS ROUGHLY 4.4 pounds LIGHTER!

I have the LPE diff in hand. It is completely welded shut just like slide 7 states "the sheet metal housing is also welded, which means that non-destructive opening of the crown gear is not possible." All of the other torsen diffs can be unbolted and taken apart. Jay has given me permission to do some destructive testing on the LPE diff, so i will hopefully have more concrete answers soon.

[Smac770]

Let's be sure to refer to the diffs by their part numbers, not the codes on the transmissions they may have come out of. That will ensure clarity in what is being discussed.

ETKA reports the center diff for a 2010 S4 with KMR transmission as 0B2 409 755 H. What came out of your KMR was an 0B4 409 751 H. Because ETKA is not saying what was used at every moment during production, it's saying "you need one, this is it". And parts.audiusa.com says 0B4 409 751 H has been replaced by 0B2 409 755 H. But that seems crazy. They aren't the same center diff. They aren't even the same topology (though I'm assume the 0B4 409 751 H is a type C like the 0B6 409 751, as it seems logical and I've found no visual information showing a dismantling to quote exactly what is in an 0B4 409 751 H).

So that Audi would replace the 0B5 409 755 K center diff in an 0B5 transmission with the 0B2 409 755 L, a center diff of completely different topology, at some point is not without precedent.

ETKA says the 0B5 409 755 K, which I say is a crown diff, was used in the A4/S4 with 0B5 with spline shaft until Oct 4 '10, at which point it changes to the 0B2 409 755 K. Which I'm pretty sure is not a crown diff. If it were, they would be no point in the three full height pillars at 120° around the outer edge. Those are clear signs of the type B Gen2, and in this case, further compacted as noted in the A7 SSP. Going sealed would help in that compacting goal. But so those six holes on the bottom are not screw holes, but oil flow holes then. Cool. And I would fully expect it to be lighter as you noted. The same is seem for the 0BL/0BK center diffs. If you have an 0BK 409 755 C laying around, it would be curious how its weight compares.

If you have an airport around you, take it over there and see if they'll let you put it through the x-ray machine. If it's functional, no need to destroy it if the question can be answered in another manner. I don't know what other facilities would have an x-ray machine, in case the airport are not as enthusiastic as we are about needing to know.

But throw up some pics once you've done a number on it. It's frustrating to try and find decent visual documentation of this stuff.

[MarkusS4]

So according to ETKA a crown diff was used until oct 4 2010 and then they moved back to a torsen? that would not make sense unless they had massive failures.

I am about to grind off the welds to open this thing up. I do not have an airport near me. I will keep everyone posted.

[walky_talky20]

I am about to grind off the welds to open this thing up.

Oh my goodness. This is *THE THING* I was hoping for when I made this thread.

[MarkusS4]

Oh my goodness. This is *THE THING* I was hoping for when I made this thread.

Im glad i can help

[MarkusS4]

So, sorry for the delay, i had some things come up. To me, this doesnt look like a crown diff. However i am not sure and i will be grinding off the other side on friday. Let me know what you think.

Cut open OB2409755K (1).jpgCut open OB2409755K (2).jpgCut open OB2409755K (3).jpg

[Smac770]

It's the T-2 / type B Gen2 compact design, as shown in the SSP for the 2011 Audi A7.
Ie, exactly what I said it was in the report pages. The cutaway is shown in slide 8.

So there's the original 50:50 T-2, then the asymmetric T-2 as shown in SSP 429 and what you see in Slide 5, then this is the compacted asymmetric T-2 as shown in SSP 478 and what you see in Slide 8.
You popped the cover off on the large end, which is the right end of the one shown in the cutaway diagram. The two small gear pairs are the same purpose as in the original T-2, but now they are staggered so one pair drives a larger diameter drive cog than the other to create the asymmetric torque split.

[MarkusS4]

So what is the difference between the OB4 409 751 H (T-3) and the OB2 409 755 K (T-2)? is it possible to use the Stasis torsen diff shims with them?

[Smac770]

I don't really get the shims thing. They seem only relevant to the old 50:50 diffs. I assume the Stasis shim thing is the same process as https://jhmotorsports.com/jhm-4-1-ce...rans-only.html

The asymmetric T-3 0AQ in the Q7 (SSP 363) has a 42/58 (1:1.381) static torque split, with a dynamic range from 60/40 to 23/75.
The asymmetric T-2 0B2 in the Q5 (SSP 429) has a 40:60 (1:1.50) static torque split, with a dynamic range from 66/33 to 15/85. That would imply a TBR of 2:1 forward and 5.5:1 rearward.

But if you consider that the asymmetric means that one rearward torque = 1.5 forward torque, the TBR to the rear is actually more like 3.75:1, and the TBR to the front is more like 3.0:1. Which seem a more reasonable ratio range.
40 front *1.00:1 = 40, * 1.50 = 60 rear
15 front *3.75:1 ~= 56, *1.50 ~= 85 rear
66 front / 3.00:1 = 22, *1.50 = 33 rear

If we take this back to the Q7 asymmetric T-3, now we see a more steady 2.33±.1:1
42 front *1.00:1 = 42, *1.381 = 58 rear
23 front *2.42:1 = 56, *1.381 = 77 rear
60 front / 2.25:1 = 27, *1.381 = 40 rear

So the actual TBRs in the Q7 T-3 are in the 2s, and I think I remember reading somewhere that number. Assuming this kind of math is even valid. It just multiplies out and makes a nice chart; no idea if it's a legitimate computation of TBR in an asymmetric Torsen.

But I've never seen a 60/40 quoted for the B8 front distribution. The usual text is 40/60, with a range from 70/30 to 20/80. Let's assume the SSP 363 numbers are particular to the 6 planet gear 0AQ. So let's assume our 5 planet gear 0B4/0B6 are different, and we end up with 3±.5:1 range
40 front *1.00:1 = 40, *1.50 = 60 rear
20 front *2.67:1 = 53, *1.50 = 80 rear
70 front / 3.50:1 = 20, *1.50 = 30 rear


So all in all, I don't really think the old school 50/50 split 2:1 TBR mod work is going to blindly apply to the asymmetrics without some engineering validation. I would think a message to someone such as JHM would be the quick answer to if anyone mods the asymmetrics.

[walky_talky20]

So, sorry for the delay, i had some things come up. To me, this doesnt look like a crown diff. However i am not sure and i will be grinding off the other side on friday. Let me know what you think.

Cut open OB2409755K (1).jpgCut open OB2409755K (2).jpgCut open OB2409755K (3).jpg

I think we need more pics.

[Audi 4 Life]

I don't really get the shims thing. They seem only relevant to the old 50:50 diffs. I assume the Stasis shim thing is the same process as https://jhmotorsports.com/jhm-4-1-ce...rans-only.html

The asymmetric T-3 0AQ in the Q7 (SSP 363) has a 42/58 (1:1.381) static torque split, with a dynamic range from 60/40 to 23/75.
The asymmetric T-2 0B2 in the Q5 (SSP 429) has a 40:60 (1:1.50) static torque split, with a dynamic range from 66/33 to 15/85. That would imply a TBR of 2:1 forward and 5.5:1 rearward.

But if you consider that the asymmetric means that one rearward torque = 1.5 forward torque, the TBR to the rear is actually more like 3.75:1, and the TBR to the front is more like 3.0:1. Which seem a more reasonable ratio range.
40 front *1.00:1 = 40, * 1.50 = 60 rear
15 front *3.75:1 ~= 56, *1.50 ~= 85 rear
66 front / 3.00:1 = 22, *1.50 = 33 rear

If we take this back to the Q7 asymmetric T-3, now we see a more steady 2.33±.1:1
42 front *1.00:1 = 42, *1.381 = 58 rear
23 front *2.42:1 = 56, *1.381 = 77 rear
60 front / 2.25:1 = 27, *1.381 = 40 rear

So the actual TBRs in the Q7 T-3 are in the 2s, and I think I remember reading somewhere that number. Assuming this kind of math is even valid. It just multiplies out and makes a nice chart; no idea if it's a legitimate computation of TBR in an asymmetric Torsen.

But I've never seen a 60/40 quoted for the B8 front distribution. The usual text is 40/60, with a range from 70/30 to 20/80. Let's assume the SSP 363 numbers are particular to the 6 planet gear 0AQ. So let's assume our 5 planet gear 0B4/0B6 are different, and we end up with 3±.5:1 range
40 front *1.00:1 = 40, *1.50 = 60 rear
20 front *2.67:1 = 53, *1.50 = 80 rear
70 front / 3.50:1 = 20, *1.50 = 30 rear


So all in all, I don't really think the old school 50/50 split 2:1 TBR mod work is going to blindly apply to the asymmetrics without some engineering validation. I would think a message to someone such as JHM would be the quick answer to if anyone mods the asymmetrics.

Yes the stasis shim mod s same as jhm from what I understand the stasis shim kit is for early production B8 A4 manuals which had t3 torsen diff.

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[SixtyFortyDiff]

I'm pleasantly surprised to see this was revived after almost exactly 1 year! Good work from MarkusS4 on the technical info and helping decipher the center diff part numbers/design changes over the years, and also from Smac770 for doing the dirty work of grinding open an LPE trans center diff and confirming it is indeed not a crown gear, but instead an asymmetrical T2 design. I'm in a Haldex platform these days, so my torque bias (front biased by default, sadly) is determined by controller maps and electrohydraulics, but I still find this purely mechanical self locking center diff stuff very interesting.

[MarkusS4]

I don't really get the shims thing. They seem only relevant to the old 50:50 diffs. I assume the Stasis shim thing is the same process as https://jhmotorsports.com/jhm-4-1-ce...rans-only.html

The asymmetric T-3 0AQ in the Q7 (SSP 363) has a 42/58 (1:1.381) static torque split, with a dynamic range from 60/40 to 23/75.
The asymmetric T-2 0B2 in the Q5 (SSP 429) has a 40:60 (1:1.50) static torque split, with a dynamic range from 66/33 to 15/85. That would imply a TBR of 2:1 forward and 5.5:1 rearward.

But if you consider that the asymmetric means that one rearward torque = 1.5 forward torque, the TBR to the rear is actually more like 3.75:1, and the TBR to the front is more like 3.0:1. Which seem a more reasonable ratio range.
40 front *1.00:1 = 40, * 1.50 = 60 rear
15 front *3.75:1 ~= 56, *1.50 ~= 85 rear
66 front / 3.00:1 = 22, *1.50 = 33 rear

If we take this back to the Q7 asymmetric T-3, now we see a more steady 2.33±.1:1
42 front *1.00:1 = 42, *1.381 = 58 rear
23 front *2.42:1 = 56, *1.381 = 77 rear
60 front / 2.25:1 = 27, *1.381 = 40 rear

So the actual TBRs in the Q7 T-3 are in the 2s, and I think I remember reading somewhere that number. Assuming this kind of math is even valid. It just multiplies out and makes a nice chart; no idea if it's a legitimate computation of TBR in an asymmetric Torsen.

But I've never seen a 60/40 quoted for the B8 front distribution. The usual text is 40/60, with a range from 70/30 to 20/80. Let's assume the SSP 363 numbers are particular to the 6 planet gear 0AQ. So let's assume our 5 planet gear 0B4/0B6 are different, and we end up with 3±.5:1 range
40 front *1.00:1 = 40, *1.50 = 60 rear
20 front *2.67:1 = 53, *1.50 = 80 rear
70 front / 3.50:1 = 20, *1.50 = 30 rear


So all in all, I don't really think the old school 50/50 split 2:1 TBR mod work is going to blindly apply to the asymmetrics without some engineering validation. I would think a message to someone such as JHM would be the quick answer to if anyone mods the asymmetrics.

Does that mean the newer T-2 has a higher dynamic range? Therefore, in theory, it is a better diff?

- - - Updated - - -

I think we need more pics.

I will get more this weekend. I had a major electrical problem at my house that has consumed my time.

[Jay@JXB]

Hi, sorry late to this conversation. Can't believe I never found this thread til now! Happy to see the pictures of my LPE diff all cut apart up there. I've very intent on making sure I have a crown gear in the race car. Since we've disproven the splined output shaft = crown gear theory, to me it seems the published Audi model year changes for the S-tronic cars is likely to be accurate. I personally have a code NAA 0B4 transmission in the race car, but I highly doubt it's crown gear. Luckily, I have an NAA 0B5 transmission out of a 2015 S-tronic S4 on it's way to me right now (if Old Dominion ever decides to deliver it). I will 100% be dismantling it the moment it arrives. Based on our PN information compiled here, I'm assuming it will be obvious if it's crown gear; but if not, I won't hesitate to cut it open. We need answers!

[Jay@JXB]

Also, here’s the center diff out of a 2011 A8 trans. Code MXR. I’ve got a few other transmissions here, but not sure many are relevant to the topic (another 0BK and a 0B2).


















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