2 4 0 T U R B O . C O M 
Volvo Limited Slip
Rear End Options

     UPDATED: June 3, 2018                       CONTACT       
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This info was compiled years ago.
Some of it may be a bit out of date.
I'll leave it up for the sake of the info it contains.
I hope it helps.

If you need some technical explanation of limited slip differentials, try here:
http://auto.howstuffworks.com/differential.htm and http://en.wikipedia.org/wiki/Limited_slip_differential

The following link goes into greater detail about available LSD's for Volvo rear ends: http://www.turbobricks.com/mods.php?content=art0014

Cutting through all the myths about just what 240's and 740's came with what type of rear end and what Limited Slip or Locker differentials will actually fit these cars has been a long struggle.  The following information has been submitted and compiled by various experienced Volvonuts over the years and will hopefully help you in making the right decisions. 

If you have any additions or corrections, or if you can provide any photos that will help with these discussions, please email me. 
Thanks, Dave Barton.

-comment from Justin Wade, dated 2002:
The below Limited Slip Differential info was confirmed by Reider Racing and MVP (unfortunately MVP no longer exists). 
It seems the LSDs available are the same for all Dana 1030 and 1031 axle cars, as it's also the same for the "standard" Dana 30 LSD. 
The catch is the gearing cut-off for the particular rear end you have.  A rear end with gearing of 3.73 and higher will be different internally from one with 3.54 and lower. 
Basically, TracTech (who offers the TrueTrac differential), and Dana only make two limited slip diffs each for the Dana 30 rear used in 240s and 740s.  One part was designated for all 1030/1031 diffs with 3.54 gears and below, and one part for all 1030/1031 diffs with 3.73 gears and above. 

It just so happens that most 1031s that you will come across will have 3.73:1 gearing or higher because of the high numbers of cars this axle came in -- mostly turbos with mostly auto transmissions, some towing package cars, and seemingly some random 5 speed cars.  One TrueTrac differential for instance, made by TracTech, carries a part number of 912A411 for 3.73 and higher cars, regardless of the variation being a 1030 or 1031 axle.  Of course, if your car came with 3.54 or 3.31 gears, you would require a different part number.  This LSD is supposed to be a very nice unit and is only a little over $300 at Reider Racing.   

Visual differences between a Volvo 1030 and 1031 Differential Case

Above photos are from Anthony Hyde's Volvo Differential page
COMMENT 12/08/02: 
Stealthfti  from the Turbobricks Forum wrote:
There are measurable differences between a 1030 and 1031 rear end housing.  A 1030 is about 10.125 inches from the rear cover mounting surface to the front of the pinion neck.  A 1031 is almost exactly 0.5 inches longer.

COMMENT 04/08/02:
Derek Walker wrote that while in the process of examining different options for an LSD for his '89 745 GLE (equipped with a 5.0L Ford engine and 4.10:1 differential), he checked with Reider Racing regarding the Trutrac per the recommendations here.  Reider responded that his 1031 Volvo housing would NOT accept the Trutrac LSD due to slight dimensional differences from the 1030 housing.  It seems they had had a few returns from Volvo owners due to incompatibility issues.  It's not clear if the issues are unique with the Trutrac LSD or the 1031 housing.

Also it does seem all 1031s have the "ears" on the right side of the pumpkin (they are not machined on 240s).  These ears attach to the torque arm on the 740 suspension.  Justin's source for the info on the "ears" and the 1031 axle is Mike Knell, who authored the Volvo V8 swap information in JagsThatRun

From reading posts on 4x4 chat groups, the Trutrac sounds like a great LSD, especially for street performance.  The Dana Powr-Loc (which appears to be the LSD Volvo offered for standard towing packages) is also supposed to be a good, long-lasting differential (although quite expensive when new)..

Trutrac Internal Components

UPDATE NOTE 02/12/04: 
tuff240 from the Turbobricks Forum wrote:
The differential units are all the same up until they changed them for the speedo tone ring. The only difference between a 1030 and 1031 is the housing itself and the ring and pinion. The differential units can be swapped back and forth. The ring and pinion cannot.

The later model cars (86 and up), which all have speedo tone rings, are believed to all be 1031's.  A Trutrac unit going in a car that requires a speedo tone ring will be different only to fit the tone ring.  You can still swap tone ring or no tone ring differentials from 1030 to 1031. The only problem will be that you won't have a working speedo if you need a tone ring and install a diff that does not have one.

AGAIN, the major difference is the Ring and Pinion.   The differential units come in 2 sizes depending on what Ring and Pinion you have or want. One will fit 3:73 and up, one will fit below 3:73.  Make sure you pick accordingly in case you ever want to change gears.  For example, you cannot change from a 3:91 ring and pinion to a 3:31 ring and pinion without changing the differential unit. This goes for stock oem diffs and TrueTrac diffs as well.
*EDIT The pinion bearings are also different between a 1030 and 1031. So make sure you get the right pinion bearing for whatever rear end you have.
I abused a 1030 rear end with 200 rwhp for about 15K miles with NO problems whatsoever.  But keep in mind I have no personal experience with 700 series cars, just 200 series cars.

UPDATE NOTE 07/16/06:
-from Matt Dupuis

I installed a Trutrac in my 244 this winter, and would like to share some info on that.

Because my car is a V8, I chose to use a 3.31:1 gear ratio, so I ordered the low-preload diff for the 3.54:1 and down (PN 912A374).  I'm using a 1031 axle from an '86+ car, so it's got the tone ring and speedo drive (I had planned on using this with my Megasquirt for traction control at a later date).  At the same time, Dale Walmsley ordered a high-preload diff for the 3.73:1 and up (PN 912A411), for his 122 which we installed into a 240 1030 rear axle.

When I got my rear end apart, I thought to measure the carriers to see if I needed to buy any different shims.  To my surprise, I needed to add about 0.120" to the ring side of the carrier and subtract that from the other side!!!  Since the factory shims are about .060" each, that meant I'd have to machine material from the carrier to get it to fit.  Obviously this wasn't the right part for the car.

So I borrowed Dale's Trutrac and measured.  It was within .001" of my Volvo diff carrier, so I installed it using the original shims and new bearings, and the gear lash was even better than it was before I pulled the old one out.

Again, I used a 3.73 and up Trutrac (p/n 411) with my 3.31 ring and pinion in my 1031, and all fit perfectly well.  I've also installed the same diff  into a 760 with a 3.73 and it fit just as well.

The taller gears (3.54 and down) have a larger diameter pinion to accomodate more teeth, so the ring gear must be moved further offset from centerline in order to keep the thickness of the ring gear consistent with shorter ratios.  Many manufacturers do this by moving the flange on the diff carrier outboard for the "highway" gears, but it seems that Volvo, in the 1031 at least, used a thinner ring gear instead, and kept the differential carrier the same for all ratios.  I can't speak for the 1030 model diff, since that's closer to a true Dana 30.  They might use thicker ring gears and offset flanges for the 3.54 and down (if they were ever delivered with those ratios).

Another thing that occurred that you should watch for.... the pickup for the speedo may drag on the Trutrac.  My 240 had a light drag, and I didn't bother doing anything about it, but the 760 I did had a HEAVY drag, so I had to clearance the sensor to clear the diff.

-from Mike Perry (mikep at Turbobricks)

Trutrac Installation notes for differentials using Speedo Tone Rings:
For the first tone ring car I installed a Trutrac diff into, I welded a speedo tone ring onto the diff.  It was a big pain. I had to cut the ring apart and weld it to the carrier, then grind down the welds, which were brittle from conduction hardening, so I had to braze the cracks.

Then I did a Trutrac install for Michael Towery.  I cut grooves with a die grinder and cutoff wheel.  It was so easy and worked so well that I only do it that way now.  The grooves need not be wide. The count just has to be the same. I think it's 12 grooves for the speedo.  I'm not sure of the count for ABS.  You can adjust the clearance by sliding the cover up or down, or by using a press in extreme cases.  I have done probably 8 of the Trutracs in total, and the ones for 3.73 gears also work for 3.31 in most cases. The PN 912A411 in the first pic is in a 3.73 geared 1031 axle (my son's car) and the PN 912A588 is in a 3.31 geared 1031 axle.  I also set up a few plate diffs and some locked (welded) for Rob's drift car. Maybe 12 Volvo axles total, not counting repair jobs.

Regarding differential part numbers... the Jeep front diff ("low preload", actually with a different hypoid angle) is a PN 912A314.  I have done plenty of these, but they slip in turns with a big rear sway.

The old number for a Volvo rear with "high preload" is PN 912A411.  I have done two of these.  The new number is PN 912A588... better case material, high preload.  I have done one.  It is the number for high gear ratio numbers, but I think it went in a low number car.

One more bit of info: The diff manufacturers list a split in ratios at 3.51 or something, however I have never found a difference.  I have measured diffs from Jeeps and Volvos with 3.31, 3.55, 3.90, and 4.11 ratios, and ALL were interchangeable. I recently put the new Trutrac PN 912A588 diff in a car with 3.73 gears, and have already put one in a car with 3.31 gears.


Jonas Borgegård of Sweden jonasbakaxel@gmail.com wrote:
I have my own company in Sweden www.bakaxel.se and I sell mostly parts for Volvo.  I sell rear axels and rebuilt BMW/ZF gearboxes to fit in Volvos and other parts.

If you wants ABS you can take the ring from the old differential and "move" it over to the Trutrac (PN912A588).  You need to put it in an machine to take away some steel to be able to get it "on" and move out the pickup for the speedometer 2-3 mm.  I have also made a CAD file and made a water cut metal "plate" that I wrapped around the Trutrac and then welded it together.

Here's a discussion thread on installing a Truetrac in a Volvo 1031 rear end:

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