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

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G80 in a 240
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Diff Sensors
Other Misc Rear End Stuff

Installing a G80 Locking Differential
(from a 700/900)
into your 240

The G80 Automatic Locking Differential is a special differential that Volvo began putting in 740/940/960 models as standard equipment (NORTH AMERICAN market only) beginning in late 1991. It was also made available as a factory option for the 240 in 1993. Volvo referred to it as the Automatic Locking Differential (A.L.D.). 

Not all 1991 700/900 models got a G80, but it should be found in all 1992 and later 700/900 Volvos (North American market). 

The G80 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 until it senses a speed difference between the axles. It then locks to provide traction to both wheels. As speed increases, the differential can sense the speed increase and it then unlocks at speeds above 25 mph.  It does this by using a centrifical weight which 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 or for OPEN or LOCKING differentials, then it's fine. 

An appropriate lube weight is 75W90. Heavier weights or synthetic lubricants may also be used as long it is rated GL-5 for CONVENTIONAL or OPEN differentials.  A G80 diff has friction plates similar to a Limited Slip differential, but they are made of metal instead of normal LSD clutch material. Adding any Limited Slip frictions modifiers to a G80 will prevent the friction plates from properly gripping when they need to.  So if you accidentally added LSD additives and wondered why your G80 converted into one-tire-fire, now you know.
Volvo 1030: 1.35 US quarts
Volvo 1031: 1.7 US quarts

Visual differences between a Volvo 1030 and 1031 Differential Case

Above photos from Anthony Hyde's Volvo Differential Page

If you intend to install a used G80 differential in a 240, it is a direct (or nearly a direct) bolt-in to the 240 Dana 30 (1031 and 1041) rear end. 
In most cases, these differentials will bolt in and run just fine with no adjustments, even without replacement of any bearings or shims.
You MUST remove and reuse your own ring gear, which matches your existing pinion gear, unless you plan to change both of those. 

If you're concerned about installing a used G80 diff "as is," you can take an extra step by also checking the ring gear backlash after installing. This is done 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 over time.

There are shims under the carrier bearings, which can be added or removed. This will adjust the ring gear closer to the pinion gear (which will reduce backlash) or farther from the pinion gear (to increase backlash). Removing bearing and changing shims will of course increase the difficulty of this installation, because these bearings are pressed on.  It can be difficult to remove these bearings without damaging them and some will tell you the quickest removal is cutting them off.
So far I have avoided having to deal with removing or replacing any carrier bearings on two different G80 installations in my 240s. In my cases I simply installed the G80s with the bearings and races that came with the differentials from the donor cars. I did not remove the bearings.

If you find yourself needing to change, pull or adjust bearings, here's a little info below that may help.

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

More information: https://forums.tbforums.com/showthread.php?t=317970&page=2

I have not personally experienced this puller 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:

There are some people who will tell you that the only "correct" way is to fit the differential just as you would a brand new differential replacement, using new bearings, shims and a professional technician. But that can be expensive.
The choice is yours, however many "junkyard" DIY mechanics (myself included) have already done this successfully as (*nearly) a simple bolt-in.
*Regarding the "nearly" a bolt-in thing: The one exception is for 1991 and older 240s. See the info below on trimming the right side axle.

 See that round silver metal disc below? 
I'm not certain of it's function, but I've seen it referred as an "oil slinger" or a "crown wheel screw lock plate" (to prevent ring bolts from loosening on limited slip differentials). You'll almost never see this plate in a photo of a removed G80 or a retrofitted one, because they're almost never re-used.  That cover is found on all Volvo G80 differentials. It covers the ring gear bolts. It will prevent you from removing the ring gear bolts if the bearing of that side is still in place. The only way to remove this cover intact is to first remove the bearing on the ring gear side. These bearings are pressed on, so removing them can damage them if you don't have experience or tools. 

  If you don't plan to remove this bearing, you can simply cut that plate 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: https://www.turbobricks.com/mods.php?content=art0027)

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:

If you remove a G80 from a salvage yard yourself, make sure you save 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. 
So 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. If your rear end is from a 1991 or older 240, you will need to trim a small amount off of the inner end of the RIGHT side axle.  This is because the right axle is a bit too long to fit all the way back in with the G80 in place.
The amount that needs to be trimmed is about 1/8 to 1/4 inch.

Sometime in 1992 the 240 was 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 installation will be a 100% bolt-in.

740/940 (non-240) Note Worth Mentioning:
The stock axles from a 1041 G80 rear end in a G80 equipped 740 or 940 are a bit shorter (and also fatter) than the stock 1031 axles in a pre-G80 car. Some knowledgeable DIY 700/900 owners have been swapping over 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.

All related to 240s with Electronic Speedometers (1986-93).
1986 and later 240s came with electronic speedometers that were triggered by a speed sensor (VSS) in the rear differential cover. There were two types.
1986-1992 240 without ABS (below left).
1991-92 240 with optional ABS (below right).
1993 240, ABS was standard (below right).

If your G80 came with a 48 tooth tone ring (standard for all ABS Volvos) and your electronic speedo 240 uses a 12 tooth tone ring (standard for NON-ABS 240s), your speedometer will not work correctly.

Some DIY installers have successfully modified the 48 tooth tone ring using a Dremel cut-off wheel.
Keep in mind that you should probably use the sensor that works for the 12 tooth ring.  And if you installed a newer aluminum differential cover from a later car, the earlier sensor might have fitment issues. For such a custom installation, some sensors may be adjustable for depth and some may need shims added or subtracted to adjust depth.
12 tooth ring: 240 without ABS (1986 to 1992). Should be adjusted to a clearance of 0.85 mm (0.0335 in) +- 0.35 mm. 
48 tooth ring: 240 with ABS (optional in 1991-92, standard in 1993). Clearance 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 can feel the rotating tone ring. 
(Source: https://forums.turbobricks.com/showthread.php?t=204882)

<<< If you need a NEW TONE RING (speed sensor strip) these are available from Kaplhenke Racing.
These are available in 12 tooth or 48 tooth size:  https://www.bneshop.com/collections/240-speed-sensor-strip

Here's a video showing this new tone ring being installed.

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, etc). And occasionally stay locked longer than it should when you no longer needed it locked.  For my street car, I'm much happier with an unmodified G80.
Modifying the G80 is optional. It has been a fairly popular fad 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). 
I agree 100% with this statement and it's what I have found with my unmodified G80.

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:

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: https://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 below has been submitted and compiled by various experienced Volvonuts over the years and will hopefully help you in making the right decisions. 
Volvo Rear Differential Part Number and Interchange Database:

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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