V2 Diff rebuild + Gear Ratio Swap

[bigjae46]

bigjae46

Also forgot to mention it and maupineda touched on it...

Let's say you put the diff together and the preload to turn a wheel is too high or low. You have to tighten or loosen the top cap which then changes the carrier preload and backlash. I've found that one full turn keeps you within the backlash spec as long as you started within the .003 to .0035 range. BUT...if you get out of BMWs spec (IIRC .0024 to .0055) then you have to remove the ring gear, reinstall the diff carrier and play with the carrier shims. Doing some math can get you really close on the first try but what a PIA if you're doing it with the case still in the car. If you get the carrier preload correct and change the shims on the side where the top cap is...then backlash should be in spec.

Or just plop in a V1 and call it the day.

[bigjae46]

I'm waiting to see what LSD unit and setup they choose for the E46 M3 diff. It sounded like he was not a fan of the Racing Diffs products or the GKN V1/2 LSD units, and he preferred ZF or Drexler components due to their high quality, OE level replacement parts.

The OE units are fine for street driving. Performance, hard to beat a mechanical clutch diff like a ZF. Now…I’m sure you can find parts but it won’t be from BMW. I dorked up an oil ring and had to have a machine shop make one.

[Slideways]

Got that down. Haven't had any issues with V1s and ZFs so far. Just the V2 in track cars. There is still preload but it's a one-tire fire on track. I'm waiting for my tech buddy to swap in a ZF unit so I can look at the V2. Could be the clutches are totally smoked, not sure. Either way it is not really worth the amount of pain and risk involved with rebuilding the V2s. They have also yet to prove that they provide any performance benefit.

I'm waiting to see which LSD unit and setup they choose for the E46 M3 diff. It sounded like he was not a fan of the Racing Diffs products or the GKN V1/2 LSD units, and he preferred ZF or Drexler components due to their high quality, OE level replacement parts.

[bigjae46]

bigjae46

Got that down. Haven't had any issues with V1s and ZFs so far. Just the V2 in track cars. There is still preload but it's a one-tire fire on track. I'm waiting for my tech buddy to swap in a ZF unit so I can look at the V2. Could be the clutches are totally smoked, not sure. Either way it is not really worth the amount of pain and risk involved with rebuilding the V2s. They have also yet to prove that they provide any performance benefit.

[Slideways]

bigjae46

[sapote]

YYes, the V1 GKN unit by design allows the whole clutch stack and gears to "float" inside the carrier, so the there is preload from the free play shim, and the big bevel washer on the clutch stack, in the V2 unit the gears are locked in place, so the free play shim basically just jams the bottom spider and side gears together which will wear them sooner.

In a nutshell the factory the gears of both V1 and V2 are floating. When you say the gears are locked in place in V2, are you referring to factory setup or RD setup? Keep in mind that the clutch stack never puts any load on the gears.

[sapote]

I tried two of these kits. Each time, the diff locked up fine but then it would quickly start not locking. Still had preload at the wheels. Really odd. The V1 kits work great.

V2: Did you torque the ring to its original position (locked with a steel ball)? Doing the way that RD shows in their video is the wrong way, that they used the lock ring to preload the breakaway at 100Nm. The V2 factory used shims to achieve the spec preload, not spring washer and the lock ring.
Btw, watching RD video that uses the threaded ring to set the breakaway torque, which had the ring stopped before the it got to the locking ball, and this means the carrier right side bearing preload is much higher than factory when using the same stock bearing shim. Too many flaws in the way RD did.

[sapote]

Another data point, the original stack height is ~14.2mm, this is on a god knows what mileage, but at least I know is not completely shot as it still has 65NM of breakaway torque.

There are some shims on top of the clutch stack. Did you include the shims in your measurement?

[bigjae46]

Should last assuming the friction discs are the same as what I got with the 4 clutch ZF kit. It has been about 4 years and still works.

I did 1 V2 in 2022 and 1 in 2023 so not sure if I got the updated kit. Tightening the ring definitely increases the preload at the wheel. IIRC, we were on the edge of the backlash spec after tightening the ring. That's the PIA. Really need a jig to check the breakaway torque before putting the ring gear on.

Oh...removing the ring gear bolts isn't too bad with a big impact. Just have someone with strong wrists hold it and blast away.

[maupineda]

Yes, the V1 GKN unit by design allows the whole clutch stack and gears to "float" inside the carrier, so the there is preload from the free play shim, and the big bevel washer on the clutch stack, in the V2 unit the gears are locked in place, so the free play shim basically just jams the bottom spider and side gears together which will wear them sooner. also, the V2 unit has from the factory 8 clutches and 9 steel plates, RD kit initially was like OE, however, they redesign the kits and now both variants get 5 clutches and 6 steel plates, however, the V2 requires a taller stack. it will be cool for those that have opened a V1 to document the stack height. but for sure is less than V2s due to the lesser number of plates.

Once I open my unit I will be able to measure the stack height of the OE clutches and compare to the RD kit.

That said, my plan is to not use any of the bevel washers, I will measure the lash and if it is the recommended value (.15 to 0.2mm) from the factory, I will leave it, otherwise, I will shim it. for the clutches, I will replace only the clutches.

This is why I did not even think about using the top collar to adjust preload, as that changes the effective unit length, which would require new output shaft shims and adjust bearing preload, so all that I plan to keep to factory specs.

I only hope the quality of the friction material is close to OE, if so, then the rebuild should last long enough.

[bigjae46]

Mine coupe at 55k miles (90k kms) is very clunky. The one I am rebuilding is a spare of known condition so will do a full rebuild. May rebuild the OE one and sell it.

i also will document what I will do for clutches and spider gear lash.

The ring is left hand thread...found that out the hard way.

I tried two of these kits. Each time, the diff locked up fine but then it would quickly start not locking. Still had preload at the wheels. Really odd. The V1 kits work great.

[sapote]

The edge around the ball is tiny (1mm), you would need a specialty bit, and a proper setup and then how would you reinsert it in place? Either tap the same location, or around the barrel.

I see. A circular grinder bit (maybe custom made) would cut the 1mm lip. I will ask my friend machinist for ideas.

[0-60motorsports]

At this point im just going to get the wavetrac LSD:

https://www.ecstuning.com/b-wavetrac-parts/limited-slip-differential/30309165wkwvt/

[maupineda]

I have 5 V2 diff to rebuild this spring, all my diffs have worn LSD or whine...

Mine coupe at 55k miles (90k kms) is very clunky. The one I am rebuilding is a spare of known condition so will do a full rebuild. May rebuild the OE one and sell it.

i also will document what I will do for clutches and spider gear lash.

[maupineda]

Do you plan to replace the output flange bearings? For reuse I would tape off the bearings during drilling to keep the metal debris off.

On the locking ball drilling: they placed the ball in the hole then peen around. I wonder if it's easier to clean the "peen" lip and get the ball out vs drilling the whole ball.

Hi Sapote, no, I will replace all bearings, clutches, and all seals. So I did not care about debris, but yes, like you say, otherwise, taping and a proper cleaning will be a must.

i don’t think it would be DIY’able. The edge around the ball is tiny (1mm), you would need a specialty bit, and a proper setup and then how would you reinsert it in place? Either tap the same location, or around the barrel.