VOLVO LSD - LIMITED SLIP DIFFERENTIAL - ANTI-SPIN
Pictures and information © by Anthony Hyde
First release Nov. 2005, Updated August 2008

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1030 Volvo LSD- MARKING e.g. 2 6 80 AH 26421 X

This webpage fills a literature & picture void on Volvo LSD internals. I hope you find the information useful. A.H. LSD FUNCTION : (Quote source - 1979 Volvo green manual) "Two shafts make up the spider for the differential pinion gears. On the side where it is against the differential carrier, each shaft has a V-shaped bevel. The differential carrier is correspondingly designed. When power from the engine starts to drive the vehicle, the shafts glide up the bevelled recess in the differential carrier. This compresses the friction plates behind the differential side gears so the differential assembly brakes (locks up). The bevel angle on the carrier is chosen in such a way that the differential gears are not entirely locked, but a maximum 75% of engine torque can be transmitted to a drive shaft."

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Five steel friction plates, side gear retainer and side gear. Same set is repeated on each axle in metal-to-metal contact in diff oil. Pic shows order - external, internal, 3rd plate cupped (like a C), internal, external.	Unexpected find on rebuild. Dana 30 LSD's fail at the spider shaft. Spider gears run either side of centre.
The 'spider' is made up of two cross-shafts that interlock and four side gears. Look closer to spot why this LSD wasn't working so well.	Spreader tool - Diff housing was spread 0.3 mm before LSD centre released (max spread 0.38 mm). Figure the tight fit ensures no endplay is possible to alter the crown & pinion relationship.	LSD - smaller carrier & larger carrier Carriers (housings) are bolted together with left-hand threads

The limited slip differential ( LSD ) was an optional extra on many Volvo models and the units were fitted at the dealership: This applied to later 140s, 240s and 740/760 models. All 240's and 7 series LSDs with the 'solid live rear axle' used either the [ Dana M30 - Dana 30 with 27 spline axles ] OR [ M31 - Dana 31 with same 27 spline axles ].
(LSDs on older 1960s-70s era Volvos used a Dana 27 with 10 spline axle eg P1800, 122 early 140's).
From 1970, the M30 (Volvo / R-Sport LSD #279951-8) was available. You can still buy new Volvo LSD's (eg. Volvo dealer, SAM). with spare parts readily available from SAM in Sweden. OR via the Volvo dealer network for most 'but not all' internal components - price logic on some dealer parts is questionable, other parts reasonable.
Note: the LSD inside 7 & 9 series diffs are different in external carrier shape and use for instance different securing bolts (socket cap head) that hold the small and large carrier together. Note: the bolt head size (same left-hand UNF thread) is incompatable with earlier LSD's as the socket cap head pokes out to far and fouls the diff housing. KEEP old LH housing bolts they will be in demand soon enough.
If you know of other changes or have information not found on the page, please email Anthony

Diff Identification 1030 and 1031 - outlined below are the Volvo versions of the Dana M30 (27 spline) and the M31 (27 spline). Volvo diffs are 1030 and 1031 (Volvo replaced the 'M' with a 10). The diff is part Volvo (Metric) and part Dana (Imperial). For example, the thread system is mostly UNF (Unified National Fine) from the tailshaft flange bolts (Front 5/16 x 24 TPI UNF. Rear diff flange 3/8 x 24 TPI UNF) all the way to the 240 wheel studs/nuts 1/2"x 20 TPI UNF (740 is M12x1.5) , and UNC (Coarse) for diff cover plate bolts and other areas. Metric threads are found on the diff ends where the dust, disc & handbrake assemblies attach. Essentially much of the transmission system starting rearward with the Laycock overdrive / tailshaft flanges / diff / use imperial dimensions and threads.

Volvo 1030 Diff - single rib M30 27 spline	The Volvo 1030 Dana 30 differential is a pretty tough unit with beefy axle diameters (1-3/8" stepped to 1-5/16") to match some V8's. The 1030 diff is most common in the earlier 240 series with 4 cyl engines and more than a few have LSDs fitted. The early days 70s-80 140/240's with their 4 speed boxes and carby engines required a greater range of diff ratios to suit customer needs, hence a full range of ratios were available (depending on markets) - 3.31, 3.54, 3.73, 3.91, 4.11, 4.30, 4.88:1. The 1030 holds 1.3 litres of oil. The 6 cylinder 260's use a 1031 with low numeric ratios eg 3.31, 3.54. Modern Dana versions are called Power Lok
Volvo 1031 Diff - dual rib M30 27 spline	1031 - Around 1981 onwards, most 4 cly 240's came fitted with the 1031 and from what I have seen in ratios of 3.54, 3.73 to 4.41. However, 264 models have been fitted with the 1031 version for years. Outside of Scandinavia, the 1031 with a LSD is not very common. John Sargent writes: "The Limited Slip Differential was fitted as a dealer option to certain 1031 rear axles. The LSD add-in for this axle is a Dana Power Lock with Volvo's name on it and a tone ring for cars with electronic speedometer." Differences : The 1031 housing is a bit stronger again than the 1030 as it has the extra rib, and fitted with larger diameter gears on the crown wheel and pinion (Volvord in Canada writes: "30 series uses a 7.2" ring gear while the 31 uses a 7.562". This small increase in diameter of the ring gear and the larger pinion gear (1.376" vs 1.406") adds up to a marked increase in strength"). The front pinion shaft diameter & bearings are larger. Note the 'LSD centre' is the same unit. If trying to fit a different diff ratio (eg. change of crown wheel) from a 1030 diff into it a 1031 diff (or vice-versa) forget it. If you wish to change diff (final drive) ratios, stick to the same diff version componentry. In summary, don't try and mix'n'match 1030/1031 parts. The 1031 holds 1.6 litres of oil. Outside of Sweden & Norway,1031 diffs with LSD are rare. Ivar Finnvik from Norway writes: we used the 240 Turbo in European Rallycross championship in the late eighties and the M31 (1031) was the one and only axle to use.

LSD for common 1030 diff

LSD for 1031 diff (rare outside of Scandinavia)

LSD for 740-940 IRS (rare)

A number of newer '1992 - '93 240's including the 'Polar' version were reportably equipped with anti-spin 'Automatic Locking Differential' (ALD) being completely different to an LSD - Jonathan Dally
Traction Control Systems -> (VOLVO 1993 TECH & SPEC) "Volvo offers several different traction control systems which vary by model. They include:
240: May be equipped from the factory with an automatic locking differential. This unit aids in initial acceleration under poor traction conditions. When one wheel starts to spin due to low friction, the differential "locks" sending driving torque to the opposite wheel as well. The system automatically "unlocks" as soon as normal traction returns or when the vehicle exceeds approximately 25 mph. This is a factory installed option." Source: Volvo Club UK.
Futher reading on ALD is on Swedishbricks Page

	Volvo Alloy Diff RARE Volvo marked ALLOY 'diff centre'. Bolting to either side of the 'centre' are steel axle tubes with standard 240 attachment points. Only fits the 1030 crown and pinion (smaller than 1031). has LSD centre inside.
	SAM Sweden offer this 'competition' Volvo Dana LSD unit. (Pic from SAM parts website)   DIFF GASKET - Modern diff shops use a silicone liquid gasket, to replace the (expensive) paper gasket. One recommendation is ThreeBond #1215 (from Japan).

How to tell if the junkyard Volvo has an LSD ? - first indicator to look for is a small metal tag (Use LSD oil) attached to a bolt on the diff cover. To mechanically check, you need to jack the whole rear end of the car up so both rear wheels are just off the ground. Rotate a wheel by hand looking whilst looking at the other wheels rotation. If both wheels rotate in the same direction its an LSD, if they rotate opposite each other its standard.
For a running car you can just do a short wheelie in the dirt and then check for equal grooves.

Dana 30 LSD's fail through the spider shaft centre hole
You certainly hear reports with one common result - my LSD worked well for 7 years behind the turbo engine before I noticed the diff not locking up like it used to. I thought the metal to metal clutch discs were worn but one spider shaft had broken instead. Others have found both spider shafts broken. I know a mechanic who has a bucket full of broken Dana spider shafts. Other LSDs have failed fairly quickly after fitting 2nd hand units behind their turbo engines - a full inspection before fitting would be advisable. Reports of Dana LSDs behind modded V8s are not good.

Jim Williams (Australia) found two broken spider shafts that inturn resulted in lunched internals. Unit was fitted to a 1969 164 manual overdrive. 3.73 ratio. Spider shaft - Volvo #3845010 - Most shafts have holes in the centre, but from what I have seen the older ones don't. IF you have information you would like to share, please email Anthony

X-Ray of 2nd spider shaft - 120kV, 150uA

X-Ray of replacement solid spider shaft

1030 Rear Wheel / Axle Bearings: 73 mm OD, Timken U360L. Diff outer oil seal Volvo #383222 (65 ID, 52 OD, 8.5 to 9 section)

CROWN WHEELS
3.73 : 1 - Volvo #384213 P05 43-11
3.91 : 1 - Volvo #384217 P06 43-11
Differential Gear Ratio determines the number of times the drive/tail shaft (or pinion) will rotate for each turn of the wheels (or ring gear).
If you have a 3.73:1 gear ratio, the drive shaft turns 3.73 times, and the wheel once.