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

     UPDATED: July 3, 2019                       CONTACT       
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Installing a G80 Locking Differential
(from a 700/900)
into your 240

The G80 Locking Differential is a special differential that Volvo began putting in 740/940 rear ends (standard in North American market only) beginning in 1991. It was also made available as a factory option for 240s in 1993. Volvo referred to it as the Automatic Locking Differential (A.L.D.). 

Not all 1991 740/940 models got them, but nearly all RWD cars got this differential from 1992-on (North American market). 

This differential was manufactured by Eaton and was designed to provide positive locking of the rear wheels during low speeds if extra traction becomes needed, typically below 25 mph (40 km/h).  The differential initially acts as an open differential and when it senses a speed difference between the axles, it locks to provide traction to both wheels. As speed increases, the differential can sense the speed change and it then unlocks and stays unlocked for speeds above 25 mph.  It does this by way of a centrifical weight that changes position as speed increases.

Here are some videos from Eaton explaining how this differential works:


DO NOT put any lubricant in a G80 differential that has Limited Slip additives or LSD friction modifiers. GM recommends GL-5 rated lubricant, but be sure to check the label. Some GL-5 lubes have LSD additives added. If the label says it's for CONVENTIONAL differentials, then it's fine.  An appropriate weight is 75W90. Heavier weights or synthetic lubricants may also be used as long it is rated GL-5.  A G80 diff has friction plates similar to a Limited Slip differential, but they are made of metal. Adding any Limited Slip frictions modifiers will prevent them from properly holding when when they need to.  So if you accidentally added LSD additives and wondered why your G80 converted into one-tire-fire, now you know.
This differential is a direct (or nearly a direct) bolt-in to the 240 Dana 30 (1031 and 1041) rear ends.  In most cases, these differentials will bolt in and run fine with no adjustments, usually even without replacement of any bearings or shims. You must remove the ring gear and bolt your own ring gear on.  If you're concerned about installing a G80 "as is", you can check the ring gear backlash after installing by using a dial caliper. Backlash is the amount of rotational movement (back and forth) of the ring gear when the pinion gear is stationary. The Volvo specification calls for around .005 to .007 inch (5 to 7 thousands of an inch) of backlash.  There are how-to videos on YouTube for checking ring gear backlash on a rear end.  If the backlash is out of spec, the rear end may whine at some speeds or there may be unusual wear.

CORRECTING EXCESSIVE BACKLASH: There are shims under the carrier bearings that can be added or removed to adjust the ring gear closer to the pinion gear (to reduce backlash) or farther from the pinion gear (to increase backlash). Changing shims will of course increase the difficulty of this installation, because the bearings must be removed and these bearings are pressed on.  It's difficult to remove these bearings without damaging them or cutting them off.

PULLING CARRIER BEARINGS (AKA: Differential Side Bearings)
So far I have avoided having to deal with replacing any carrier bearings on two different G80 installations in 240s. I installed them with the bearings and races that came with the G80.
If you find yourself needing to change, pull, adjust bearings, here's a little info.

If you have the correct Volvo bearing puller tool, then allegedly pulling these bearings can be done without damaging them. 
Without this tool, it is supposed to be more difficult to remove these bearings without damage (requiring new bearings), but if anyone can offer better info that what I have here, please email.

More information: https://forums.tbforums.com/showthread.php?t=317970&page=2
<<< I have not personally experienced this tool, but it looks pretty good in the below videos:

Here's a video of an interesting carrier bearing puller made by Matco (Part Number MST4520) that appears to be doing very well on a carrier bearing: 

And here's the OTC version (PN 4520), which looks identical to the Matco: https://www.youtube.com/watch?v=-eh8WF_ON6g
There are some that will tell you that the only "correct" way is to fit the differential just as you would any other new differential replacement, using a professional technician. This can be expensive. The choice is yours, however many "junkyard" DIY mechanics (myself included) have already done this successfully as a (*nearly) simple bolt in.
*Regarding nearly a bolt in: Exception for pre-1992 240. See Axle Trimming info below.

 <<<  See that round silver metal disc?  That's a cover (AKA: oil slinger) that you'll almost never see in a G80 photo (because they're almost never re-used or re-installed).  That cover is found on most (maybe all) Volvo G80 differentials on the ring gear side. It will actually prevent you from removing the ring gear bolts, which must be done to install your own ring gear.  The only way to remove this cover intact is to do what the person in this photo did; to remove the bearing on the ring gear side. These bearings are pressed on, so removing them usually damages them. 
<<< There's another way to deal with this. You can simply cut that disc off with tin snips and toss it.  That way you can swap your ring gear without having to mess with pulling/installing new bearings. (Photo borrowed from G80 modification article:
Here's a YouTube video of someone pulling a G80 from a Volvo at a salvage yard and you can see this disc on that differential: https://www.youtube.com/watch?v=wwQh9mMtmvE
If you remove a G80 yourself, make sure you keep the bearing races and mark them RIGHT and LEFT with a marker so they end up on the same side as they were originally.
If you're shopping for a used G80, keep in mind that this differential was used in a lot of different cars and trucks. Some have different axle spline counts. 
<<< The ones used in Volvo cars are made for a Dana 30 with 27 spline axles (identified as a 1041 axle). All such differentials from a Volvo it will have "VOLVO" and a Volvo part number stamped into it as shown here.
The part numbers seem to be pretty various and seem to have changed a number of times over the years.

BEWARE: I have seen that some on-line sellers REMOVE the carrier bearings before selling a G80.  If you want the bearings INTACT, be sure to check that before buying.

This is the part that makes this installation nearly a bolt-in instead of a 100% bolt-in. In most cases when fitting this differential to a 240 rear end, you will need to trim a small amount off of the inner end of the RIGHT side axle.  This is because the right axle will not fit all the way in with the G80 in place. The trim amount is about 1/8 to 1/4 inch.  In 1992 the 240 changed so that the right side axle was slightly shorter. This means that some 1992 and all 1993 models will not need any axle trimming and this will be a 100% bolt-in.

<<< If your G80 came with a 48 tooth tone ring and your later 240 uses a 12 tooth tone ring, many DIYers have successfully modified the 48 tooth tone ring using a Dremel cut-off wheel. Keep in mind that the sensor mounted in the differential cover may need the depth adjusted, especially if you installed a new aluminum differential cover from the later G80 car. Some sensors are adjustable and some will need shims added or subtracted to adjust.
A 12 tooth ring (typical to 1986 to 1991 240 without ABS) should be adjusted to a clearance of 0.85 mm (0.0335 in) +- 0.35 mm.  A 48 tooth ring (typical to 1992 and later 240 with ABS) should be 0.6 mm (0.024 in) +0.2 mm (0.008 in), -0.3 mm (0.012 in). 
Check your clearance with a feeler gauge through the filler hole. Turn the pinion as you do so to check clearance. Start with a thin gauge and go thicker until you feel the rotating ring.  (Source: http://forums.turbobricks.com/showthread.php?t=204882)
740/940 Notes Worth Mentioning:
The stock axles from a 1041 G80 rear end in a G80 equipped 740 or 940 are a bit shorter (and fatter) than the stock 1031 axles in a pre-G80 car. Some knowledgeable DIY 700/900 owners are swapping in both axles from a G80 car when fitting the G80 in their earlier 740s and they fit just fine. Cutting a right side axle is only for a 240 installation.

Yours truly has run both a modified one and unmodified one in my 242. I currently have an unmodified one installed and I'm happy with it.  The modified one I used to have was a bit problematic.  It would occasionally lock and unlock the left and right alternately in traction limited settings (drag strip). And occasionally stay locked longer than it should when you no longer needed it locked.  For my street car, I'm happier with an unmodified G80
Modifying the G80 is not required, however it has been a fairly popular thing among hot-rodders. A modification is done to the G80 before installing to alter the internal locking mechanism. Altering the internal mechanism can be done to make it stay locked through higher speeds or to even stay locked at all speeds.  But at least one person says, "Even an unmodified G80 will stay locked at much higher speeds than 25 as long as the power is increased. I've had stock units stay locked up until at least 60 mph in turbo cars." (Source: https://forums.tbforums.com/showthread.php?t=240436&page=2 Post #78).

If you decide you want to modify your G80, this can be done by a couple different methods and these are outlined in the article links below. Not all of the methods are the same, so if this part interests you, read it all.

<<< You can begin by reading this modification tutorial in Turbobricks: https://www.turbobricks.com/mods.php?content=art0027
More resources below.
Below Video:  Disassembling and Modifying a G80


Limited Slip Info for Volvo Rear Ends
This info BELOW was compiled years ago.

So some of it may be a bit out of date.
I have left it up at the request of users 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 submitted from Justin Wade, dated 2002:
The below Limited Slip Differential info came from Reider Racing and MVP (unfortunately both companies 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 end 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 in turbo cars with mostly auto transmissions, some towing package cars, and seemingly some random 5 speed cars.  One TrueTrac differential for instance, 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. 

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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