Here's What Goes Into Making A Geared Limited-Slip Differential

We had a poke around Quaife's Gillingham factory to find out what goes into a making an ATB differential
Here's What Goes Into Making A Geared Limited-Slip Differential

Most petrolheads will probably have a vague idea of what a limited-slip differential does, but have you actually wondered what they look like inside, and how they go together?

We have, and with Quaife - one of the most well-known manufacturers of the things - right here on our British Isles, we thought we should pay a visit to its factory, to see lumps of steel get transformed into one tyre-fire killing works of magic.

While Quaife does produce a small amount of plated differentials, its mainstay is its ATB (Automatic Torque Biasing) differential. It’s a geared differential working on a similar principle to a Torsen, and as such isn’t able to fully lock. However, while a plated diff only locks to 50/50 across an axle, an ATB diff can send up 80 per cent of torque to one wheel.

We’ll delve into the differences between a differential like this and a plate-type differentials another time, but as Quaife is constantly making ATB units, it’s possible to rock up to the factory and see the whole production process in one hit. Here’s what we discovered…

Casing

Here's What Goes Into Making A Geared Limited-Slip Differential

Here’s how every Quaife ATB differential starts out: as a chunk of steel billet. This goes onto a CNC lathe, and 10 minutes later, we have something that looks like this:

Here's What Goes Into Making A Geared Limited-Slip Differential

It’s the right shape, but the inside is smooth and requires shaping so that the gear set fits in nicely. Five housings go into a massive CNC milling machine at a time, which does its work in around 40 minutes.

Remote video URL

Each differential has a pair of side or ‘sun’ gears - one for each half shaft. As with the casings, these start off as pieces of steel billet, which are passed through an auto-loading CNC gear cutter.

A conveyor belt feeds the billet into the rear of the machine, with a two-sided robotic arm removing the previously completed gear, before rotating and picking up the fresh billet for the next gear cutting job. It cuts one a side gear a minute, and is rather mesmerising to watch.

The gear isn’t finished at this point though, as it needs to have a spline cut in on the inner circumference. The cog is sent to a massive machine that pulls a long bar through it, cutting in the spline that’s needed for the sprocket to mesh with the end of its corresponding half shaft.

Remote video URL

Next up, we have the worm gears. Each ATB unit has 12 helical-cut (as opposed to straight-cut) worm gears, which transfer torque between the two side gears and - as a result - between either half shaft.

These start off as - you guessed it - steel billet. Each piece of billet is put through a hobbing machine to be cut, before being sent off-site for heat treatment.

Final assembly

Here's What Goes Into Making A Geared Limited-Slip Differential

All finished components are assembled by hand, generally in batches - although we asked to see one differential built up on its own to get a better idea of how it fits together.

After the top part of the casing is bolted down and torqued up (the bolts are the only part of the diff to be manufactured off-site), the assembled unit is sent through a CNC grinder, before having a quality check using a coordinate measuring machine (CMM).

Here's What Goes Into Making A Geared Limited-Slip Differential

Finally, the ATB diff is finished off with some laser etching, is wrapped up and loaded up with a bunch of other completed units to be shipped away to mainstream manufacturers, distributors, specialist companies and individual customers. Most of the differentials you’ve seen built here are destined for Ford, where they’ll be fitted as part of the Ford Focus RS ‘option pack’.

Sponsored Posts

Comments

Sir Wafel (WhyBeAre of CT) (Multipla Squad) (propane)

I think CT is drunk

08/19/2017 - 11:59 |
30 | 4
Kyle Ashdown

Great article! Now I don’t have to Google “how to make LSD” anynore!

08/19/2017 - 16:17 |
70 | 2

now you wont have the government looking at you anymore

08/19/2017 - 16:44 |
8 | 0
M4R10

I thougt it was witchcraft….until i watched the video

08/19/2017 - 18:27 |
6 | 0
TheBagel

insert Wii home screen music

08/19/2017 - 22:41 |
4 | 0

God no!

08/21/2017 - 12:07 |
0 | 0
Anonymous

I k

08/20/2017 - 01:58 |
2 | 0
Anonymous

Yirkw

08/20/2017 - 01:59 |
2 | 0
Joseph (Prelude Squad)

Ok I now now how there made now can someone please tell me how to find one for an A2K5 transmission?

08/20/2017 - 04:44 |
2 | 0
AX53

“its mainstay is its ATB (Automatic Torque Biasing) differential. It’s a geared differential working on a similar principle to a Torsen, and as such isn’t able to fully lock. However, while a plated diff only locks to 50/50 across an axle, an ATB diff can send up 80 per cent of torque to one wheel.”

Wut? lol.. 50/50 across an axle means each wheel is capable of putting down 100% of the power. And that is somehow a bad thing? 80 percent torque to one wheel just means that it will rob the power from the other wheel which most likely is the wheel that needs it. This is such a bogus marketing statement.

08/20/2017 - 07:23 |
2 | 0
Gabz

In reply to by AX53

I have one of these diffs and it’s great. Instead of locking the two wheels together it puts as much traction on each wheel as they can handle. If the inside wheel can only get traction with 20%, the outside one still receives 80%. My S2K used to lock up all the time in tight bends while my 330ci (quaife) puts all the power down and slingshots out of corners. I love it!

08/24/2017 - 09:03 |
0 | 0
Anonymous

want :O

08/26/2017 - 02:49 |
0 | 0