VAC Motorsports - 335i, 135i Performance Built Differential - How we do it!

[Brian_VACsales]

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Hey guys,

A number of folks were wondering what our banner ad means when it says 'precision work done in house on our CNC machines.' I am proud to say that we in fact do everything in house - nothing is outsourced.

As many know, most 335i and 135i models have a challenging stock differential. Unlike most cars, most 335i and 135i models have a differential where the ring gear is WELDED to the unit. Note: Just about every car on the road has a ring gear that is BOLTED to the unit.

In order to add a Quaife, Wavetrac, OS Giken unit to your 335i or 135i, you need to re-use the ring gear and pinion in your differential. Not so easy since the ring gear is WELDED to the stock unit!!

So, in order for us to upgrade to a Quaife, Wavetrac, OS Giken etc. we put our machines to work and created this incredibly accurate process to to separate the ring gear from the carrier and prepare said ring gear it to be bolted to the new aftermarket unit.

This is a quick tutorial. We wanted to do the best job possible, so we configured our CNC lathes and mills to handle this challenging task. The end result is beautiful =)

How is a VAC Performance Built Differential made (this is not a complete list, but most major operations are covered)

1. Photograph and inspect every differential for damage/missing parts etc.

2. Drain and inspect fluid looking for shavings or anything odd with the fluid.

3. Remove cover, inspect ring gear, confirm gear ratio. Pictured: The infamous welded ring gear. Note how it is actually welded to the carrier.






4. Test backlash before dissassembly.

5. Remove axle shafts, old side cover seals, snap rings.

6. Carefully remove the carrier.

7. Remove inner races from carrier.

8. Clean up the carrier, and prep for CNC operation.

9. Set up the carrier in our ultra rigid and precise CNC lathe. Pictured: Stock welded ring gear/carrier on one of our lathes.



10. Machine away weld that secures the ring gear to the carrier. This is an extremely robust weld.





11. Remove the resultant step (weld) so it is flat enough to machine. Pictured: stock ring gear separated from carrier.



12. Machine the ring gear flat (to ensure a precise mating surface for the new unit) Pictured: Separated ring gear | fully machined ring gear | drilled/tapped ring gear



13. Set up the newly finished ring gear on our CNC mill. Pictured: Machined ring gear on our HAAS 5 axis machine.





14. Machine the ring gear to make it compatible with the limited slip unit.

Pictured: Completed ring gear still in the HAAS mill.



Before:


After: Note how we machine the entire face, not just the area where the LSD bolts. Our machining method ensures ideal accuracy and reliability. Not sure that anyone takes it this far.



15. Assemble the limited slip unit.

16. Pressure wash and paint the housing.

17. Soda blast and clean the differential.

18. Install bearings/snap rings.

19. Check pattern, install seals, gasket material and differential cover. Pictured: Checking the pattern on the newly assembled differential.


20. Tag and prepare for install/shipment. Pictured: VAC Performance Build Differential with optional Billet Differential Cover.

[beemerman1984]

Do want... Would go perfect with my M3/Ground Control suspension, diff is my weakest link still. Whats something like this run? Can you change the gearing to offer better acceleration?

[BSM 135i]

wow, some quality craftsmanship you guys got going on, love that diff cover!

[Bdh821]

Awesome work! PM me the price of diff cover please!

[Focusedintntions]

Beautiful. Need to win the lottery for one of these asap lol

[5teN]

Very impressive. Nice to see you share the details of your operation.

Could you please PM details of LSD options and cost?

Cheers

[Dackelone]

Really cool photos of what all is involved with this mod. A lot of us dream about getting a LSD for our 1er's . Thanks for posting.

[Tommeh]

There is two different cooling fin lengths if i remember correctly.

[Mark16q]

I didn't think I wanted an LSD, but this has me drooling. Beautiful work, and seeing how easy it looks on the post, should be pretty cheap, right ?

[Tommeh]

Anyone seen any pictures installed on a normal car? Only 135i I have seen this on is that all carbon fiber track car someone is building.

[BFD99]

Please pm me price as well!

[Brian_VACsales]

Thanks guys!

All PMs were replied to. Thanks for the interest.

[Colt]

PM me price too, just for shiggles.

[Focusedintntions]

They have a group buy going on right now for anybody interested.

[Turbolader]

That sir, is some spectacular work.

[brusk]

If you join the group buy how soon do you have to send your diff in? how much does the entire thing weigh to get an idea for shipping costs across country.