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TruTrac Install in a 1031 axle

gsellstr

Vintage anti-ricer
300+ Club
Joined
Oct 21, 2004
Location
BFE Desert east of Cali
Ok, so I finally got to installing a TruTrac 912A588 into the stock open diff 1031 in my wagon and figured it's time to update some data out there on the web. First off I'd like to thank Dave Barton for the page he's got, as well as update it a little.
http://www.davebarton.com/volvorearends.html

First off the identification of a 1031 is not quite correct. A 1031 and a 1041 can be a single-rib axle, and a 1030 can be a dual-rib axle (have a 1030 in the 140 with 2 ribs). The axle the TruTrac went into was a 1031 with a single rib and the 1041 that was in the car was also single rib. The 1031 has the larger inner pinion bearing as well.
The 1031:
IMG_2528%28Medium%29.jpg

<o:p> </o:p>
Now for the meat of the project…
Parts required:
New pinion nut spec’d for the Volvo axle (the Dana 30 nut is not the right size)
New crush sleeve (not included in my kit, others may have it)
TruTrac 912A588 (bought along with install kit from <st1:city><st1:place>Summit</st1:place></st1:city> – search the web for a price match and they’ll meet it)
IMG_2520%28Medium%29.jpg

<o:p> </o:p>
Dana 30 rear install kit
IMG_2529%28Medium%29.jpg

IMG_2530%28Medium%29.jpg

<o:p> </o:p>
Timkin HM89449 bearing and HM89410 race (bought from Autozone)
This is the pinion bearing that’s different from the 1030 and the standard Dana 30. The one on the left is the 1031 bearing, on the right is the 1030/D30 bearing.
IMG_2519%28Medium%29.jpg

<o:p> </o:p>
Tone ring from a G80 or skills to make something similar if it’s going into something that requires a speed pickup. The later ones use a 48-tooth ring like shown here, but others may have a 12-tooth ring.
Here’s the G80 tone ring
IMG_0013%28Medium%29.jpg

And the stock open diff tone ring
IMG_2531%28Medium%29.jpg

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Now for the work…
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It’s easiest to remove the axle from the vehicle, but it CAN be done without. Once you’ve got the axle where you’ll be working on it the teardown begins. First the axles come out, then the cover comes off and the old diff comes out. You probably won’t need a case spreader for this part (I didn’t). If you’re doing bearings as well the pinion nut and flange need to come off and then you can tap the pinion gear out with a punch in the center of the gear to avoid damage to the threads.
IMG_2522%28Medium%29.jpg

IMG_2524%28Medium%29.jpg

<o:p> </o:p>
You’ll need to split the bearing or press it off and press the new one on making sure to keep the shim in place between the gear and the bearing as this sets your pinion depth. From here the pinion gear can go back in, the new crush sleeve, new outer bearing, the oil slinger (goes right between the bearing and the flange), the flange, and nut. Torque the nut until you get around 2Nm of turning torque.
<o:p> </o:p>
Now for the diff. First off the old bearing needs to come off the ring gear side so you can remove the oil slinger, the ring gear bolts, and the ring gear. The oil slinger doesn’t fit well on the TT so I left if off when mine was reinstalled. Using the new bolts from the install kit you can install the ring gear. Torque spec is 26 ft.lbs plus 60* of rotation.
IMG_0024%28Medium%29.jpg

<o:p> </o:p>
The tone ring will require a little light welding. I used a G80 tone ring which was easily removed from a spare unit by using a cold chisel to split it, then simply pulling it out. The diameter is just slightly too small for the TT housing, so it will be a little short. I chose to fab up an extra tooth of the same size which worked out quite well, and kept the speedo dead on.
IMG_0025%28Medium%29.jpg

IMG_0026%28Medium%29.jpg

<o:p> </o:p>
Once you’ve got the ring welded together you need to set it on the diff at the right location. I used the speed sensor hole to set the installed position, by centering the ring in the hole for the speed sensor.
IMG_0021%28Medium%29.jpg

<o:p> </o:p>
Once that’s on a few tack welds to keep the ring in place and you’re set.
IMG_0027%28Medium%29.jpg

<o:p> </o:p>
Next you need set up the differential in the housing. You’ll need a dial indicator to do this correctly. I have the setup tools which made this part FAR easier. You will need a way to put the bearings on the diff, remove them, then reinstall them with the correct shims if you don’t have the proper setup tools. Once you’ve got the bearings on you need to set the differential for .005-.006” backlash, plus .05-.08mm of bearing preload. Once you’ve got the shim combination for each side figured out, pull the bearings back off, install the shims, reinstall the bearings, the diff into the housing, and the bearing caps (torque to 22 ft.lbs. plus 60*).
At that point you should end up with something like this…
IMG_0028%28Medium%29.jpg

<o:p> </o:p>
Now for the final steps.
You will need to space the speed sensor out about .010” due to the larger diameter of the tone ring. A layer of thin gasket material works for this if you use a diff cover gasket. If you don’t use a diff cover gasket you will need a little thicker spacer. You’ll be able to tell if the sensor will hit easily enough by putting the cover on and using an axle shaft to spin the diff.
<o:p> </o:p>
At this point you’re ready to install the cover and the axle shafts, fill with oil, and install in the vehicle. Fill capacity is 1.6L for the 1031/1041 axles. I chose Redline 75w90 for mine and it seems to be working quite well.
<o:p> </o:p>
As for the performance, mine’s only been in the car for a day but it’s completely seemless. You really don’t notice it’s there until you really get on it. One wheel in the dirt and the other on the pavement will get you a lot of dust in the air on accel, but the car will get moving quite quickly. One possible downfall which bit me today is if you’re hard on the throttle to a point where both sides break loose you WILL have the tail end trying to pass you up if you’re not paying attention. A hard stab in first had me in this situation when both tires hit a paint mark and let loose. Otherwise normal driving you don’t notice it’s even there, even in parking lots and such.
<o:p> </o:p>
Hopefully this helps a few of you out there!<o:p></o:p>

EDIT: 11/11/16:
Recent findings pertaining to axles with a steel cover.

Pulled the cover from the 1030 in the 140 which also has a Trutrac, since the cover plug no longer sealed (a shop years ago ran it in too far). Grabbed an aluminum cover from a 1041, bolted it on (FYI, you need longer bolts, get them with the cover, or get that length in 5/16x18 if you're working on a 140). Upon filling it up, it took 1.5qts, where the steel cover combined with the TruTrac would only take 1qt.

r9LW0BJl.jpg

iS6UDtHl.jpg


Just a cool fun fact.

For those of you needing a tone ring for this installation, here's a discussion about them:
http://forums.turbobricks.com/showthread.php?t=317562
And a supplier:
http://bakaxel.se/catalogsearch/result/?q=Hastighetsmätarkrans+

Specs:
index.php
 
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I had one of these installed in my 242. At the same time I had a Getrag installed and poly engine mounts. There is a ton of driveline noise especially when deccelerating and my friend said it might be due to not shimming the lsd correctly. The getrag came in a "kit" from my friend who took it off his 242 with balanced driveshaft, new ujoints, center bearing so it wouldn't seem to be related to that. I may PM you sometime in the future because I am swapping everything to a new rust free 242 and want to check the shimming and everything else.
 
I've got NO driveline vibrations whatsoever with HD engine mounts, full poly front to back, Koni SA's, etc. so I'd guess there's something else playing into your issue. When you get around to it certainly shoot me a pm and we can see what's going on.
 
My Truetrac also makes a TON of noise. At first I thought the lash was set up wrong but it's been working well for quite q few thousand miles.

I like it. engagement is very predictable. There are times it doesn't engage (such as when one tire has 0 traction or the speed differential is close to that), but overall it's a great maintenance free unit.

BTW I'm also running Redline 75W90. Apparently dyno oil is recommended, but meh.
 
Great write up Gary!
Perhaps as a standard variable for the G80 tone ring and 1031 combo you might be able to state this for ease of installation...
IMG_0026Medium.jpg
 
good guide. answer to the last picture anybody? :)

912A588 is that the right nr no mather what gear ration on the rear axle?
who sells it the cheepest?
 
Thought these were the guys which do this clingclingcling chainrassle sound when doing turns ? like in that one video i dont find right now..
 
The 912A588 is the correct diff for our cars, regardless of gearset. The gearset is specific to the housing though I believe. There's also the older variant if you find it used, the 912A411 that also fits our cars. I have that one in the 140 and the 588 in the wagon, no discernible differences between the two while driving. As for current best price, Summit isn't bad these days, not sure if you can find it much lower.

Wow, didn't realize it's been in there for 5 years already! Not a hint of maintenance nor issues, the slight gear whine I had initially went away as the gears re-settled after being reused, and it still holds the power and gets the tail out when asked. The ONLY thing that stands out is turns while under decent power it will chatter a little as the inside tire slips, but that's only on hard turns and a good bit of throttle.
 
My Truetrac also makes a TON of noise. At first I thought the lash was set up wrong but it's been working well for quite q few thousand miles.

I like it. engagement is very predictable. There are times it doesn't engage (such as when one tire has 0 traction or the speed differential is close to that), but overall it's a great maintenance free unit.

BTW I'm also running Redline 75W90. Apparently dyno oil is recommended, but meh.

I've never heard any noise from my true trac but i also ran the correct fluid for it.
 
good guide. answer to the last picture anybody? :)

912A588 is that the right nr no mather what gear ration on the rear axle?
who sells it the cheepest?

Yes. Correct part #. Summit Racing has it for $499.

As for distance, just do like the guide says and line it up in the speedo window.
 
I've never heard any noise from my true trac but i also ran the correct fluid for it.

Which is? I just bought one for the 8.8 (has yet to arrive) so I'd like to know before installation.

Any one of you drag raced his car with the truetrac? How was it?
 
Which is? I just bought one for the 8.8 (has yet to arrive) so I'd like to know before installation.

Any one of you drag raced his car with the truetrac? How was it?

Much easier to launch than with a pegleg diff. It's also more annoying to get traction again if you overcook the launch.
 
Which is? I just bought one for the 8.8 (has yet to arrive) so I'd like to know before installation.

Any one of you drag raced his car with the truetrac? How was it?

When I called tech support they told me to use standard gear oil, no synthetics or modifiers.

What ever weight was recommended for stock but not a synthetic. The explanation to me was that a synthetic is a little too slippery for the gear style diffs and it decreases the effectiveness of the unit. Considering you want the gears to semi bind for it to transfer power, it makes sense to me that you don't want the most slippery fluid.
 
All my timeslips on my wagon are with the Trutrac, except the early years when it was open. Launched pretty nice off the line, at least as much as the tires would allow for. Traction issues are tire related more than diff related at this point. :)

I've been running Redline 75w90 in the 140, M1 75w140 in the wagon since the gears were a little loud, both still lock up quite well.
 
Gary, in your write up you said you added a tooth to your tone ring and it didn't throw off your speedo. I cant quite figure out how this is possible, as each slot registers as a fraction of a turn. I would imagine that it would change your speedo reading by a factor of (n+1)/n. On your tone ring that would not make much difference because it has a lot of teeth. I would imagine on the 12 tooth tone rings, it will read about 8% faster than it should be. Furthermore, that error will be propagated through an integral when the odometer integrates the speed signal into position.

How did you determine that it reads correctly?

Based on my understanding of how hall sensors signals are conditioned to determine speed, I believe you would have to have the same number of teeth as OEM. It might even be better to just leave a gap than to add another tooth, because it just knows n amount of impulses are in a rotation, and the diff spins fast enough the speedo probably wont notice the delayed impulse due to the gap.

I'm leaning towards waterjetting a new tone ring with the same number of teeth but larger gaps, I can post the dxf files when I get to it if anyone is interested.
 
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