Ford Sierra Front Differential

Apologies for the delay in writing a new blog, but things have actually been happening behind the scenes. The MT75 gearbox is away with the brother in law, getting the new bell-housing welded on. I’ve been stripping and cleaning loads parts etc etc etc.

4×4 Kit Car

To state the obvious, the Ford Sierra 4×4 front diff sits next to the sump and is approx 20cm from the centre line of the car. The Engine is directly mounted above the drive-shaft. As you can see from the photo (left) the Sierra Diff bolts up directly to the sump and is effectively suspended by the engines’ mounts. It is closer to the gearbox (top of photo) than it is to the front of the engine (bottom of photo).

With a 4×4 Kit Car such as my Haynes Roadster, the engine is much further back, with the drive-shafts passing in front of the engine.

4x4 Haynes Roadster

So basically, I needed the central dive-shaft that passed through the centre of the sump, but I didn’t need the bulk of the sump itself. Apart from how ridiculous it would look if I popped the hood, it would also stick out the front of the nose-cone.

The Sierra Cosworth Sump is a beautiful piece of casting and they are probably getting fairly scarce, but I had a free one and it was going to get hacked up.

Ford Sierra 4x4 Sump

The picture below shows, that so far I have just removed the excess. I haven’t tidied things up much or at all. Besides, much of what you see here will be hidden inside a larger aluminium tube, which I haven’t sourced yet

.4x4 Haynes Roadster Front Differential

As you can see, at this stage there is not much left. I will be TIG welding a far amount back on; to triangulate and solidly hold this shaft to the diff. I’ll also be adding in some mounts so I can mount the differential to the chassis and a plate to strengthen the casing of the supposedly weak front diff casing.

Sierra Front Diff Offcuts

There is a gallery of me hacking up the diff here

There is more Sierra Differential Repair / Maintenance information here.

There is a There is a gallery of images here here.

Once I have all this work complete I will have to remember that I need to get the ratios changed over in the rear diff. Currently, I have the rare 3.92:1 Sierra 2.0lt front diff and a 3.62:1 Escort Cosworth rear diff.

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Sierra Cosworth 4x4 Front Differential

I cut up a sump from a Ford Sierra XR4x4 (It might have been a Cosworth??!?) to make a custom differential shaft housing. I added some strenghtening hollow tubes and two thick aluminium plates. The remants of the sump, were then TIG welded to the new material to form ...

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Sierra Front Differential Part II

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Sierra 3.9:1 Front Differential

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Sierra 4x4 Front Driveshaft Cover

This Sierra 4x4 Front Driveshaft Cover forms part of the Cosworth front axle assembly normally bolts to the nearside of the sump. In this design however, it will be mounted to a custom axle assembly. The cover would normally bolt to the right hand side of the sump / shaft assembly ...

Ford Sierra Front Differential Cover

This project will use a Ford Sierra Front Differential 4x4, 3.92:1 front differential (from a non-Cosworth Sierra 2.0s 4x4). Normally this diff would bolt to the alloy sump with integral drive shaft. However, for this application the diff will be mounted in front of the engine, with a custom drive-shaft assembly. ...

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