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freelander versus sierra diffs
dexion7 - 28/11/10 at 09:20 AM

just wondering about the relative strengths of freelander versus sierra rear diffs for a busa turbo. i've heard stories about freelander diff failures whilst still fitted in a freelander (the viscous coupling seizes and this overloads the diff).

later freelander diffs had bigger bearings but i dont know if this helped. the sierra diff is heavier and has more external ribbing to give the case added strength. the rear cover is also very thick which presumably helps too, whereas the freelander has a simple pressed steel cover. folks running high power 4wd cosworths often fit a steel strengthening plate on the front diff, sandwiched between the diff body & the cover to add rigidity - would this help on a freelander diff.

what is the failure mode of freelander diffs when in a bec?

any thoughts or experience?

Paul TigerB6 - 28/11/10 at 09:58 AM

As you say, the Freelander diff failed for a specific reason. For that reason, i'd personally look to source a brand new diff seeing as the price is pretty reasonable really (about £450) but then would expect you wont have any issues at all. After all, the Freelander is a heavy car and has a lot more torque (especially the diesel) than a Busa will give.

Compare the price with a 2nd hand Sierra diff with the suitable 3.14 ratio and the price difference is negligible (I sold one a couple of years back for £350).

I wouldnt worry about strengthening it further - even with a busa turbo

minitici - 28/11/10 at 10:12 AM

I may be wrong but I thought the Freelander rear diff was an 'open' type rather than a viscous coupled LSD.
The Freelander uses a viscous coupling (VCU) in the propshaft and this is the one which fails.

Most people who use the Freelander differential seem to fit a Quaife ATB LSD to the Freelander case.

[Edited on 28/11/10 by minitici]

Paul TigerB6 - 28/11/10 at 10:33 AM

quote:
Originally posted by minitici
I may be wrong but I thought the Freelander rear diff was an 'open' type rather than a viscous coupled LSD.



It is indeed an open diff. I've come to the conclusion for my own build that an open diff is a better option (more a road car rather than trackday car), with sticky tyres to maintain traction. My old car had a Cortina rear axle with Quaife ATB fitted from when i built it, but this time round i'll try the open diff first. I recon its a safer option for the road

JoelP - 28/11/10 at 12:42 PM

freelander is also 7kgs lighter.

Its understandable that it would break if the viscous centre diff locked up, driving on tarmac with a locked centre diff will break any 4wd transmission given time.

adithorp - 28/11/10 at 06:11 PM

Failures on Freelander diffs were the early smaller bearings going. Later larger bearing ones haven't suffered the same failure as far as I know.

Advantages of Freelander are the weight and ratio (3.21:1). Disadvantages, only one ratio available, quaife only option for LSD, drive shafts will need to be modified to fit.

Sierra 3.14 diffs (prefered ratio for BUSA) are like rocking horse droppings and priced to match.

adrian

ps. I've got a Freelander reconditioned open diff with about 500miles on it going spare...