Does anyone know of a limited-slip differential that'll fit the multi-link 780 rear end? I've never tackled one before - are any parts interchangeable with the solid-axle rear ends?
Thanks!

The Dana 30 axles in other RWD Volvos can fit a Detroit True-Trac for limited slip performance. I don't know whether this unit can fit or be modified for the IRS axles. If it's a Dana axle as well, I'm sure some upgrade is available for it.
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Rob Bareiss, New London CT ::: Roterande Fläkt Och Drivremmar!

If I remember correctly, you could have a Limited Slip Differential fitted to your vehicle at the Volvo dealer, -and it was available for both the fixed live axle and the 760/780 Independent Rear Suspension. Starting in 1991, all the turbo vehicles started shipping from the factory with Eaton Locker units.

Gotta run, coffee shop is closing.
God bless,
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 252k miles.
'88 Black 780, PRV-6, 146k miles.

They won't even discuss it since Volvo NA has recommended against it.

FWIW, even a stock volvo turbo can slide the back end around in the rain with a one-legger....you want to REALLY make it squirrely with a locking diff?

Problem is apparently the torque comes on too fast with the turbo to control w/o some type of electronic (ergo the later limited slips that only worked to 15mph BTW) stability so Volvo NA won't authorize it and the dealers won't do it.

I DID discuss having a limited slip diff for a Dana 30 installed at a 4X4 shop up in Laurel MD and the guy said he'd never done one before on a volvo but was willing to try. The guts were/are available from some guys in Seattle or thereabouts (MPD?) but the more I looked into it I didn't want to do it with a guy who hadn't done one before. There are other issues such as the speed sensor ring (sometimes the carrier has to be machined to accept the correct ring, i.e., number of teeth is critical) that is also used to actuate the rear ABS.

Here are a few links that should provide some more info, including one from Dave Barton:
http://personal.linkline.com/dbarton/SpecSheet.html#differential
http://brickboard.com/FAQ/700-900/Driveline.htm#LSDIfferential
A similar discussion on TurboBricks
Another Turbobricks thread
http://www.pbase.com/blkaplan/true_trac_install Pictures of a Tru-Trac installation in a late model 240.

FYI, I believe the Eaton Locking units were standard equipment on all '91+ Turbo vehicles, '92+ 960 vehicles, '94-'95 940 vehicles, and the S90 and V90 vehicles in '97 and '98 that came with the "Cold Weather" package. If you can find a donor car with the parts you need, you're home free (assuming both vehicles are (either IRS or non-IRS). I do not know if you can swap the Eaton Locker parts between an IRS and a non-IRS differential, since many of the sedans and most of the wagons were equipped with a fixed live axle, you may or may not find a plug-and-play solution.

God bless,
Fitz Fitzgerald.
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'87 Blue 240 Wagon, 252k miles.
'88 Black 780, PRV-6, 146k miles.