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Project SVT - Ford Focus SVT

Part 5: Wheel Spin, Both Of Them

Jay Chen
Nov 21, 2006
0605_sccp_01_z+project_svt+ford_focus Photo 1/1   |   Project SVT - Ford Focus SVT

The beauty of blowing up your car is that it provides an opportunity to change all the parts you never thought you'd get to. Since we destroyed the engine in Project Focus SVT right after writing Part 3, the car and its powertrain have been torn down and strewn across the floors of various shops in Southern California.

That saved us the hard work of pulling the transmission to install an LSD-a necessity when putting down big, Cobra-spanking horsepower numbers. Now, it's simply a matter of tossing the compact front-drive tranny into the back of Project Scion tC and heading down to Autotech Sport Tuning in San Juan Capistrano, California.

2017 Ford Focus
$16,775 Base Model (MSRP) 18/25 MPG Fuel Economy

Autotech is the North American distributor for Quaife Engineering products. As it turns out, the limited-slip differential options for the Focus SVT's (and MINI Cooper S's) Getrag 6-speed tranny are, well, limited. While there are technically two LSDs available, we could only locate one: the Quaife Automatic Torque Biasing (ATB) differential. Tochigi Fuji Sangyo makes a techno-wonderoo hybrid differential using both clutch plates and helical gearing to control torque bias, but we've had no luck finding one. Our choice was obvious.

Cracking open a front-drive tranny to change out the differential is a daunting task. That's why we took the tranny directly to Autotech to perform the install. But thanks to the SVT's unconventional transaxle design, installing the LSD turned out to be easier than in most independently-suspended rear-drive platforms. Autotech had the tranny back together within an hour.

It's easy because the Getrag's dual layshaft design uses two intermediate pinion shafts. Using two pinion shafts with three gears per shaft, instead of one long pinion with six gears, allowed designers to package the tranny in the narrow confines of the Focus' engine bay.

Each pinion shaft has its own final-drive gear that simultaneously turns the differential ring gear, which makes the differential easy to get at, without having to actually pull apart individual gears on the pinion as on conventional trannies.

All you have to do is crack open the transmission's case and pull out the stock diff. The differential is held in place by two tapered bearings, which need to be put onto the new limited-slip unit. Yanking the original bearings off the stock differential is a pain, and you'll most likely end up with damaged bearings. Instead of reusing the stockers, we picked up new replacement bearings to press onto the LSD.

You can't just call up your local Ford dealer and ask for differential carrier bearings though. Most dealers won't even know that the SVT uses a different transmission than the MTX-75 five-speed found on the stock, econobox Focus. Even if you find a dealer that specializes in SVT products, the bearings won't have a part number, since its not a part dealerships can order or replace. It took us a couple of weeks to figure this out.

Eventually, we resorted to measuring the stock bearing's dimensions and ordering replacement pieces: SKF number LM501349, from a local bearing supplier, at $35 a piece. Once we had the bearings, it was just a matter of pressing them onto the LSD, transferring the ring gear and installing the unit.

Although our unit didn't need to be shimmed, the tranny case had to be test-assembled with the new differential installed, then tested for axial play. If the diff can be moved from side to side with the tranny case closed, then the bearing needs to be shimmed. Otherwise, use some gasket material and seal the gearbox up.

Quaife recommends using their 75-90w Silkolene synthetic gear oil for a smooth running torque biasing diff. If not, either OEM or Mobil 1 is good, but Quaife warns against Red Line Light Shock gear oil.

All that's left is to assemble the engine and car so we can test all the new parts.

Next time, we'll install new forged pistons and connecting rods from JE Pistons, and maybe even add a clutch and lightened flywheel. Who knows, we might even get to test out all our new parts sometime in the next decade

BUILD COST SO FAR
2003 SVT {{{Focus}}}: $17,480
PTE turbo kit: $3,995
{{{GT}}} Fabrication downpipe: $450
GT Fabrication misc.: ${{{200}}}
FocusSport partial installation: $375
{{{Odyssey}}} PC680 battery: $148
FocusSport torque mount: $99
SCT reflash: $350
Michelin {{{Pilot}}} Sport PS2 tires: $692
Spray paint: $15
Mounting/balancing: $50
Progress rear bar: $199
Cosworth head work: $1,800
Quaife limited-slip differential: $1,195
Total: $27,048
Minus 2003 SVT Cobra: $34,750
Total left to spend: $7,702

Previous InstallmentsApril 2003Part 1: Starting from scratch

June 2004Part 2: Finally, a turbo

September 2004Part 3: T minus 0.7 seconds

January 2006Part 4: Another step towards resurrection

The SVT's dual-layshaft transaxle design uses two intermediate pinion shafts with three gears on each shaft. Both shafts simultaneously mesh with the ring gear on the differential, which makes removing the stock diff a matter of simply cracking the tranny open and pulling it out-without disassembling any gearing.

Although the stock differential carrier bearings can be reused, it's not worth the effort to reuse them. We ordered replacement bearings and pressed them onto the new differential.

The factory ring gear needs to be swapped onto the Quaife unit. Installing it is a little tricky since the tolerance is tight and all the bolts need to be torqued down evenly.

Most ford dealers won't even know that the SVT uses a different transmission than the MTX-75 five-speed found on the stock, econobox Focus.

By Jay Chen
85 Articles

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