V2 Diff rebuild + Gear Ratio Swap

[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]

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.

[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.

[sapote]

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. .

This is the wrong way to adjust the clutch preload as RD shows in their videos.
shim the clutch instead.

[maupineda]

I have bought a Bauer impact wrench. I hope it works.

Harbor Freight has a deal going on and for 90bucks you get the 5ah battery, charger, and a 3/8in 450lbft tool.

I’ll try it tonight.

[sapote]

I have bought a Bauer impact wrench. I hope it works.

Harbor Freight has a deal going on and for 90bucks you get the 5ah battery, charger, and a 3/8in 450lbft tool.

I’ll try it tonight.

Removing the ring gear bolts? Good luck, but I used long breaker bar and creative way to hold the carrier.

[bigjae46]

I have bought a Bauer impact wrench. I hope it works.

Harbor Freight has a deal going on and for 90bucks you get the 5ah battery, charger, and a 3/8in 450lbft tool.

I’ll try it tonight.

Yeah, I think most really big impact wrenches will work.

M12 - 100nm + 50 deg
M14 - 100nm + 30 deg

Got those from Thayer Motorsports. Not sure why the M14 has less angle?

I've seen 110 ft/lbs + loctite as well. That's what I did. Definitely a 2 person job unless you have a really good vise.

Should have M14 bolts unless you are using a earlier ring gear. I think pre-E46 - E39 and earlier - all used M12s. So if you get an old 3.91 it will have M12 bolts and you'll need the bolt hole spacers.

[maupineda]

Yeah, I think most really big impact wrenches will work.

M12 - 100nm + 50 deg
M14 - 100nm + 30 deg

Got those from Thayer Motorsports. Not sure why the M14 has less angle?

I've seen 110 ft/lbs + loctite as well. That's what I did. Definitely a 2 person job unless you have a really good vise.

Should have M14 bolts unless you are using a earlier ring gear. I think pre-E46 - E39 and earlier - all used M12s. So if you get an old 3.91 it will have M12 bolts and you'll need the bolt hole spacers.

mine are true M items, so M14s. I have the vice and everything so I won’t have an issue bolting them. It is the removal that is tricky as I can only lock the vice table in the direction of tightening

[bigjae46]

mine are true M items, so M14s. I have the vice and everything so I won’t have an issue bolting them. It is the removal that is tricky as I can only lock the vice table in the direction of tightening

remove is easier. Remove the bolts. Partially thread 4 bolts and then tap on the bolts to get a space between the ring gear and LSD housing. Then chisel on the back of the ring gear. Make sure there's a rag under the LSD unit when the ring gear comes off.

[maupineda]

I was partially successful. Was able to open the carrier but could not remove the ring gear. The tool I got is not powerful enough, so do not buy lol

To be able to open the carrier, I used zip ties to make sure the tool was fully seated on the carrier cap, this was enough to be able to tap it with a hammer.



Then tap it away!!



After a few hits, it was obvious that the cap started to spin. See the hole I had tapped before, it confirms displacement



A few more taps until you can remove it by hand...



Now, since I was not able to undo the ring gear, I had to pry on the bearings, dont do this if you are not replacing them, in my case, I am, so it did not matter. It did not take much force, just push gently until you feel it start to move.



Now the viscolok pump comes out.



Now you have access to the inner guts, there are the clutches



I took the spacer gear, which is the one that spin the clutches, the steel plates gear up to the outer inner teeth in the carrier. The thickess of this gear is what you can use to define the max clutch+steels stack before having preload, per design, there does not seem to be preload.



As you can see below, the clutch pack is no thicker than that spacer gear



Also, the viscolok pump bottoms out on that ledge above teeth to which the steels mesh up



So, the assumption that you can adjust preload by tightening the pump locking ring is partially incorrect, as the pump seats on that edge within the carrier, and that is the limit. what would allow some "pre load" adjustment is if you have a clutch stack a bit thicker than the spacer gear, but only if it is compressible, like the pre load shims RD provide. I don't plan to use those, but rather just replace the friction (clutch) plates.

Many say the GKN unit is a bad unit, I don't think so, is actually a nice engineering bit of kit as it allows for no lock, to "100%" lock.

I need to clean all up so I can measure the thickness of the steels and clutches to compare VS RD kit.

[bigjae46]

So, the assumption that you can adjust preload by tightening the pump locking ring is partially incorrect, as the pump seats on that edge within the carrier, and that is the limit. what would allow some "pre load" adjustment is if you have a clutch stack a bit thicker than the spacer gear, but only if it is compressible, like the pre load shims RD provide. I don't plan to use those, but rather just replace the friction (clutch) plates.

Many say the GKN unit is a bad unit, I don't think so, is actually a nice engineering bit of kit as it allows for no lock, to "100%" lock.

I need to clean all up so I can measure the thickness of the steels and clutches to compare VS RD kit.

I guess it is to a point. We got more pre-load when we tightened the ring. We got the entire kit, so there is an additional shim needed?

Either way, the GKN unit is fine for the street. Any high performance use without traction control on, the GKN unit is too slow. It needs wheel slip before it starts to lock so the car is starting to rotate, the driver unwinds the wheel and then the back end will still rotate then the diff locks and then the rear oscillates the other direction - tank slapper. A good driver is conservatively going to be about 1-2 seconds faster on a 1:50 lap with a ZF.

[sapote]

I was partially successful. Was able to open the carrier but could not remove the ring gear. The tool I got is not powerful enough, so do not buy lol

.

I kind of guessed this.
i used a long breaker bar. The bolts were thread locked.

[maupineda]

I kind of guessed this.
i used a long breaker bar. The bolts were thread locked.

why would I break a wrist, I am getting a big mama impact and the return it once done. no need to sweat it more than enough.

Since these bolts are monsters, it is also more than safe to reuse them.

[sapote]

Is the locking ring bottomed on this step? If it is then one cannot tighten the ring for preloading the clutch.



"the clutch pack is no thicker than that spacer gear"
Pic above seems to show the spacer gear is below the top clutch stack shim. No?

"Now, since I was not able to undo the ring gear, I had to pry on the bearings, dont do this if you are not replacing them, in my case, I am, so it did not matter. It did not take much force, just push gently until you feel it start to move."
I think one could pry the clutch stack up via the carrier side holes instead on the bearing.

"The thickess of this gear is what you can use to define the max clutch+steels stack before having preload, per design, there does not seem to be preload."
If no preload then one can spin one wheel with the other on the ground but this is not the case, and this means clutches are preloaded, and without using a spring washer. Keep in mind the pump movable piston is thicker than the center static part which is pressed on the 'spacer gear' to define the spider gears backlash.

[sapote]

why would I break a wrist, I am getting a big mama impact and the return it once done. no need to sweat it more than enough.

Using a long breaker bar is safer than an impact gun in term of wrist breaking issue. The force on the wrist is less compared to holding impact gun.