Rear End Options
|UPDATED: February 10, 2019 CONTACT|
M A I N S
G80 Locking Differential
(from a 700/900)
into your 240
|The G80 Locking
Differential is a special differential that Volvo
began putting in the 740/940
rear ends (North
American Market) in some cars beginning in
1991 and nearly all from 1992 and later. 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:
Volvo 240 owners have
discovered that this differential is a direct (or
nearly a direct) bolt-in to the 240 Dana 30 (1031 and
1041) rear ends. In many cases, these
differentials will bolt in and run fine with no
adjustments, usually even without replacement of any
bearings or shims. Many people just bolt on the
original ring gear and install. If you're
concerned about installing one "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.
There are shims under the carrier bears that can be added or removed to adjust the ring gear closer to the pinion gear (to reduce backlash) or further from the pinion gear (to increase backlash). Changing shims will increase the installation difficulty, because the bearings must be removed and these bearings are pressed on. I don't think they can be removed without damaging them, so new bearings would likely be needed to do this.
There are some that will tell you that the only "correct" way is to fit the differential just as you would any new differential replacement, using a professional technician. This can be expensive. The choice is yours, however many "junkyard" DIY mechanics claim to have already done it successfully as a (nearly) simple bolt in.
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 acually prevent you from removing the ring gear
bolts, which must be done to swap the 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 is
another way. You can
simply cut that disc cover off with tin snips and toss
it. That way you can swap your ring gear
without having to mess with the bearings.
Here's a YouTube video of someone pulling a G80 from a Volvo at a salvage yard and you can see this disc cover on that differential: https://www.youtube.com/watch?v=wwQh9mMtmvE
|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 axel spline counts.
<<< The ones used in Volvos are made for a Dana 30 with 27 spline axles and if it came 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.
| TRIMMING THE RIGHT SIDE AXLE:
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. This is the only part that is not a direct bolt-in. The trim amount is about 1/4 inch. In 1992 the 240 changed so that the right side axle was shorter. This means that some 1992 and all 1993 models will not need any axle trimming.
It's also common for modifications to be made to the G80 to alter the internal locking mechanism. It can be altered to make it stay locked later or unlock at a higher speed, 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 in turbo cars." (Source: https://forums.tbforums.com/showthread.php?t=240436&page=2 Post #78).
If you decide you want to modify yours, 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.
AND DISCUSSION LINKS:
Disassembling and Modifying a G80
|Limited Slip Info
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.
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.
between a Volvo 1030 and 1031 Differential Case
Above photos are from Anthony Hyde's Volvo Differential page
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.
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)..
UPDATE NOTE 07/16/06:
installed a Trutrac
in my 244 this winter, and would like to share
some info on that.
-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.
UPDATE NOTE APRIL 2008:
Jonas Borgegård of Sweden firstname.lastname@example.org 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.
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