[Alfalessalfisti]

I notice that the owners manual lists the following differentials:

RDU 195
RDU 230-TV
RDU 230 LSD
RDU 210/215 LSD

There apparently used to be a catalog or spreadsheet detailing each on the ZF website but it has been removed.

Which are we supposing is the the differential listed by centerline?

Let me make a few assumptions here. Coming from the Subaru world I would think that the numbers above refer to the diameter of the ring gear in each rdu. Also, zf apparently calls these rear drive units, hence the name. I would suspect the centerline unit is the 210/215 LSD. The 230tv I believe is the QVs torque vectoring unit. If that is the case I would think it would be overkill for the 2.0 cars to have the 230lsd with the same size differential (sans the planetary differentials and electric motors) as the QV. But if that is the case, good on Alfa.

I’m just trying to reach a conclusion here. Because, if the unit in the 2.0 giulias are the 210/215lsd then they may be the same or a similar unit to the zf hag rdu 215 utilized by the f3x 3 series. If that is the case, and bmw purchased the unit from zf as Alfa does, there are several aftermarket options for Lsds

Turner motorsports offers upgrades for the zf hag 215 diff, link provided below. Now the biggest issue with these is that zf welds the ring gear to the differential carrier. Thus, machining is necessary to provide an aftermarket lsd a means to affix itself to the ring gear. At any rate these are their options:
https://www.turnermotorsport.com/p-...f3x-335i435i-manual-limited-slip-and-gearing-differential-upgrade/?pdk=AQEBAQEB

Again I’m making a lot of assumptions but I feel like I’ve researched as thoroughly as I could to get to this point. Perhaps the rdu 195 is the q4 front diff? But I believe that is supplied by magna and would have a different name. Perhaps the 195/210 are open diffs and European cars are offered with different sizes than us cars? The 215lsd could be for 6 speed diesel cars and the 230lsd could be the clutch type listed at centerline.

In the end, I’m not sure but thought this might be helpful. The ti performance pkg unit is certainly better than an open diff but it won’t be anything like an OS Giken. Perhaps @MacGeek could provide further insight?

 

[Racer Z]

I notice that the owners manual lists the following differentials:

RDU 195
RDU 230-TV
RDU 230 LSD
RDU 210/215 LSD

There apparently used to be a catalog or spreadsheet detailing each on the ZF website but it has been removed.

Which are we supposing is the the differential listed by centerline?

Let me make a few assumptions here. Coming from the Subaru world I would think that the numbers above refer to the diameter of the ring gear in each rdu. Also, zf apparently calls these rear drive units, hence the name. I would suspect the centerline unit is the 210/215 LSD. The 230tv I believe is the QVs torque vectoring unit. If that is the case I would think it would be overkill for the 2.0 cars to have the 230lsd with the same size differential (sans the planetary differentials and electric motors) as the QV. But if that is the case, good on Alfa.

I’m just trying to reach a conclusion here. Because, if the unit in the 2.0 giulias are the 210/215lsd then they may be the same or a similar unit to the zf hag rdu 215 utilized by the f3x 3 series. If that is the case, and bmw purchased the unit from zf as Alfa does, there are several aftermarket options for Lsds

Turner motorsports offers upgrades for the zf hag 215 diff, link provided below. Now the biggest issue with these is that zf welds the ring gear to the differential carrier. Thus, machining is necessary to provide an aftermarket lsd a means to affix itself to the ring gear. At any rate these are their options:
https://www.turnermotorsport.com/p-...f3x-335i435i-manual-limited-slip-and-gearing-differential-upgrade/?pdk=AQEBAQEB

Again I’m making a lot of assumptions but I feel like I’ve researched as thoroughly as I could to get to this point. Perhaps the rdu 195 is the q4 front diff? But I believe that is supplied by magna and would have a different name. Perhaps the 195/210 are open diffs and European cars are offered with different sizes than us cars? The 215lsd could be for 6 speed diesel cars and the 230lsd could be the clutch type listed at centerline.

In the end, I’m not sure but thought this might be helpful. The ti performance pkg unit is certainly better than an open diff but it won’t be anything like an OS Giken. Perhaps @MacGeek could provide further insight?

My understanding is about the same as yours, including the guesses.

The three digit number is the diameter of the ring gear. The general assumption is, 'the larger the ring gear the stronger the differential'. I will argue that the ring gear is not the weakest link. The side gears and spider gears are the weakest link.

Most open differentials have two spider gears and I've seen them break, generally from being hammered on doing drag race starts. Generally speaking, an LSD of the same size will have four spider gears making it twice as strong, able to withstand more abuse.

Having a bolt-in ring gear allows for changing the ring and pinion so you can change the gearing. This isn't something that can be done on the fly, or even at the track. The serious racer would have multiple pumpkins (differential housing) all ready setup with different gearing. Then simply swap pumpkins at the track. Purpose built track cars are designed with quick change read-ends as well as quick change transmissions and transmission gearing.

 

[Alfalessalfisti]

A little necromancy here but I think I have further (assumed/deduced) insight into the diff situation. I did some digging through the dodge/jeep parts catalog and discovered that the SRT Durango and Grand Cherokee come with a RDU 230 equipped with clutch type LSD with electronic control. Hellcats/Demons have the same 230mm differential, but only the Durango and GC have cases that resemble the mounting hardware seen on Giulia differentials. Some Charger owners have swapped these differentials, or older non-electric clutch type LSDs, into their open-diff cars. However this requires a change in axles as well. Since the OEM/Centerline LSD is plug and play, not requiring lager axles, I am assuming that the following is an accurate breakdown of the differential mystery:

RDU 195: Open front differential on Q4 cars (this is also the front differential on Durango/GC).
RDU 210 "elsd": Open rear differential on non ti performance pack Giulias (misleading as elsd is brake actuation).
RDU 210/215 LSD: Clutch/plated type LSD on Ti performance pack cars (23% lock on accel 46% decel).
RDU 230 LSD: Simply the open differential situated between the TV planetary gear-sets on Quads.

This all needs to be confirmed, but I have spent a truly dumb amount of time trying to figure this out. If this is indeed the case then there may be a few possibilities. A company called Racing Diffs has confirmed that the 210/215 LSD can accept their upgraded clutches that offer increased lock. They also stated that until they can get their hands on an open diff 210 RDU, they cannot confirm that aftermarket LSDs that fit BMWs will necessarily fit Giulias. Apparently, ZF tends to have small variations between spider gears on their open differentials. And even if they can be equipped to open diffs, the ring gears are still welded to the carrier, necessitating modification.

Again, just my $0.02.

 

[RomeoBear]

I have also tried to get a BMW specialist who machine ZF diffs to fit Quaiffe. They were not interested in trying for Alfas.

When I put the question to Quaiffe this was their response
"We have looked into it, but the issue is that we are not looking to get involved in the machining off of the crown wheels, so we looked at whether we could source new crown wheels from Alfa Romeo (or directly from ZF) but were unable to purchase them.
It would need a customer that has capability to carry out the machining on a case by case basis, which means a high up front capital investment.
In short, it is not currently financially viable for us to develop an ATB diff for this car.

If you have any further questions or I can be of any assistance in the future, please don't hesitate to contact me."

So until a specialist thinks there is a market for this and invests its not going to happen. Did speak to an independent that offers Quaife for most other alfas. The have had a look into this and did some research with Quaife. Quaife will only do batches of 10 so need an order of at least 10 people. He first would need an open Diff that quaife would then destroy to make the first diff. So would come from a scrapped car. Then once the first had been manufactured it would then be a case of swapping out the diff from each car 1 and then machining off the crown wheels to attach the new ATB diff.

All got a bit complicated. So we decided to drop it. If the numbers for an order of 10 are out there and someone sees a scrapped open diff car selling parts. Happy to pick up and see if there is a way to order. Im UK based so if people were in US they would need to find a company able and willing to machine then weld back on the quaife diff local to them.

 

[Alfalessalfisti]

Thank you for sharing that, it is very helpful. I know Bimmerworld and Turner Motorsports do, or used to, install a variety of LSDs or TBDs into diffs with the welded ring gear. Of course the cost is substantially greater to have that done. It appears that Wavetrac offers this service for 210/215 equipped BMWs. I know they don't have the pedigree of Quaife, but I believe they are the only torque biasing differential that can still operate when one wheel is lifted/loses traction.

It would seem that for the foreseeable future, the best option is the factory ZF unit and shimming or installing aftermarket clutches if greater lock is desired.

 

[Crisdeto]

The lsd is a clutch type from ZF and is only installed in the rear axle. Lock up percentages are apparently 23% on accel and 45% on decel. There is not an lsd in the front because the front doesn't always get power. According to Andy Forrest, time attack guy with absurd subaru builds, the effectiveness of a front lsd is reduced when the torque bias greatly favors the rear axle, as is the case in the Giulia. According to other members on the forum, Q4 with the lsd is a money setup. Generally it reduces asr/tc/esc intervention and allows you to enjoy the car mostly free of electronic spoils.

I bought the racingdiffs kit fot my Q2 differential (giulia 2.0 280hp Q4), and in their video tutorial they assembly the differential with 45% on accel and 23% on decel. It's working to invert the pressure plates (therefor the locking ramps)? or I have to assembly same as original? I attached a video for explain you better, pay attention when they disassembly e assebly again the pressure plates, they invert them. Thank you

 

[dj_splash4004]

Hi @Crisdeto I'm in the process of retrofitting a LSD on my RWD Giulia and was wondering if the Clutch upgrade you mentioned is worth the buy.
Have you or for that matter any1 else on the forum installed this ? How's the feeling/difference?

Thanks!