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1030/1031 Differential Talk (ratios, identification, tools, theory etc)

aristg

aristg

El Greco Capitano
300+ Club
Joined
Sep 19, 2013
Location
Greece
The factors that lead to this research:
  • A grinding noise that can be heard from the rear when the car is travelling with speed (for example 80-100km/h), in gear (usually in 3rd, sometimes in 4th) and the gas is let. As the car is slowing down this grinding noise can be heard. When the clutch is depressed or when in no gear the noise is not heard. I am not sure if the same happens on the 2nd gear due to high revs at that speed. The M90H on the car and the center bearing support have been rehauled (described in my build thread) so i assume that they are not the source of this problem. Also there seems to be nothing hitting the chassis (exhaust or anything else) that could cause this noise and nothing can be heard when in low speeds or when accelerating under any conditions. Pinion preload/bearing/depth as well as carrier backlash should be checked as IMO these could cause such noises.
  • My TrueTrac equipped diff has a ratio of 3.73 which combined to the M90H and the power of the car which is 400whp+ i feel that a 3.54 or 3.31 would be more suitable. According to Dave Barton's site the latest M47 240's featured a 3.31 ratio. Of course these ratios are hard to find new, will have to take this into account. The ones that are easily found are 3.15 and 4.10 and up. I have not driven cars with these rear end ratios, so any input would be acceptable. Here are some tables with different rear ratios at given rpms (2800 and 7200 rpm).

    2800.jpg​

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    7200.jpg​

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  • Despite my feeling that my axle is a 1031 (probably swapped by the previous owners many many years ago), given that it features a 12 tooth electronic speed reading system, i will have to solve this mystery. No sticker or anything indicates what kind of diff this is. The following picture found online indicates that the pinion nut is different in size (M20 - M24) so this is something to be verified, but it looks reasonable. Funny enough when i installed the TrueTrac many years ago, i never thought of measuring the ring gear to see what kind of diff i have !

460608411_1306275300352048_1777426803718019897_n (Medium).jpg​

All of the above can be answered in one way only as it seems, which is to remove the diff, inspect, rehaul and replace the gears. However since there is no shop around that i can trust for this job, i decided to prepare as good as possible to do it. I have also decided to make my own copy of the basic special tools that Volvo used, that will help with accuracy as well as to try doing it in one shot. I really don't want to repeat the procedure until i get things right.

Tools and theory:

Pinion depth: This is usually measured from the upper face of the pinion head (carrier side) to the axle centerline. It is referred as Nominal Pinon Depth (NPD) which is 2,250" / 57,15mm for Dana 30 and this is the basis of the diff tools. This assumes a pinion that is marked as 0 (ie no shims needed set pinion depth). There is another measurement called master housing depth (MHD) which should be 3,625" / 92,07mm for Dana 30 (this will have to be checked). The Master Housing Dimension (MHD) is the distance between the axle centerline and the back of the pinion head including the shims which adjust the pinion depth. Basically the two measurements are the same but they have different reference point. Hope that these make sense !

Diff tool: Here is a pic of the diff tool used for the Volvo diff (you need to read the greenbook or watch the video to understand how this works).

Screenshot 2026-02-27 175753 (Small).png

Screenshot 2026-02-28 072523.png​


Tools 2284, 2393, 2595, 2597, 2600 and 2841 are common for 1030 and 1031 while 2685 is for 1030 and 2840 is for 1031.

If anyone has got access to tools 2685 or 2840, 2595 & 2841 please let me know to ask for some measurements. I could not find any info on those!

Tool 2284 has a dimension of 279,40mm x 16,15mm but it is really not important as long as it can support the dial gauge and be really straight !

Tool 2393 is used as such:

Screenshot 2026-02-27 195740.png

Screenshot 2026-02-27 195811.png

Screenshot 2026-02-27 195849.png

​
Basically what is needed to be done is to compare the reading of the gauge dial at zeroing point 2 and the top of tool B. This should be adjusted with shims to the number that the pinion head indicates. Lets assume for checking our measurements a perfect pinion with 0mm deviation.

From my research (and precious help of Gary - gsellstr) the total height of part B is 72,21mm. Also the diameters at number 3 is 76,45mm and at number 2 is 30,04mm.

Remember that this tool measures NPD which should theoretically be 57,15mm measured to the axle centerline (hence the half of the tool's thickness at point 2) so let's check the numbers:

72,21 - 30,04 / 2 = 72,21 - 15,02 = 57,19mm which is very close to the theoretical 57,15mm of Dana 30.

So the tools are based on the Dana 30 dimensions and they can be constructed with the above dimensions. The deviations are probably there due to measurement errors.

Tool 2685 or 2840 are used to adjust the pinion height easily so you don't have to press a bearing on the pinion, test with the above procedure and then if unsuccessful remove the bearing, change the shims and then press again, test etc .. This of course could be solved with an old bearing but still .. this tool makes life easier ! If anyone has access or info, please let me know for some measurements !


Also for carrier backlash adjustment rings 2595 i also have no info, so if anyone has access or info, please let me know for some measurements !



Screenshot 2026-02-27 203502.png​

IMO the most important tool is the one for the pinion that we now got some info about.

Sources:
  • https://www.240.se/litteratur/tp30039_2.pdf greenbook referring to the rear axle. Can be found in many places.
  • https://www.jeepforum.com/threads/cj7-dana-30-rebuild-and-setup.1121189/ A very nice thread about rebuilding a Jeep Dana 30 differential, with minor differences to ours
  • An ancient video on using the diff tool that greenbooks refer to. Unfortunately in Swedish, but i managed to translate it. If someone has some upload space or something i can upload it with external subtitle files. I have cut the video into 2 pieces, the first 30 minutes and the second the rest, since the AI translator had some limitations. Let me know if you are interested ! I will attach the subs files here anyway.

 

Attachments

Comprehensive write up. My 940 sedan when coasting in drive between 40 - 50 mph has a whistle sound coming from the differential area. It sounds like gear wine to my ear. It’s on my list to investigate at some point. I drained the diff last fall and the gear oil looked fine.
 
Led said:
Comprehensive write up. My 940 sedan when coasting in drive between 40 - 50 mph has a whistle sound coming from the differential area. It sounds like gear wine to my ear. It’s on my list to investigate at some point. I drained the diff last fall and the gear oil looked fine.
Click to expand...
Well .. forgot to mention that in the past i had shot a video of my gear whine .. around 120 km/h plus or minus 20 km/h


Car has made lots of progress since then, but the problem didn't change at all..

Never solved it with any kind of oil, so the grinding noise described above may be the next level of the same problem .. :lol:

However, when i installed the TrueTrac, i remember that backlash was 0,15mm so spot on the specs. All these years i was avoiding this diff job, but probably now there are more than one reasons to dig deeper into this subject !
 
I have most of the tools including several of the 2393. I have 2685 and 2595 but not 2840. They are essentially the same id and od of the bearings (but slip fit) and are threaded inside so that the width is adjustable. Setup bearings are easier to use and likely far cheaper than the Volvo tools. There's just a lot more trial and error involved. Even with the special tools you may need to make some adjustments as the shims will compress when the bearings are installed.

The pair of 2595's and 2600 aren't shown as I acquired them after this pic was taken. 2841, which is used for adjusting 2685 and 2840 threads onto the pinion gear so there should be a different one for the larger threads on a late1031. There's another tool that takes the place of the diff flange so that bearing preload can be checked without having to press the flange on and off and tools for removing and installing the flange.
DiffTools.jpg
 
hiperfauto said:
I have most of the tools including several of the 2393. I have 2685 and 2595 but not 2840. They are essentially the same id and od of the bearings (but slip fit) and are threaded inside so that the width is adjustable. Setup bearings are easier to use and likely far cheaper than the Volvo tools. There's just a lot more trial and error involved. Even with the special tools you may need to make some adjustments as the shims will compress when the bearings are installed.

The pair of 2595's and 2600 aren't shown as I acquired them after this pic was taken. 2841, which is used for adjusting 2685 and 2840 threads onto the pinion gear so there should be a different one for the larger threads on a late1031. There's another tool that takes the place of the diff flange so that bearing preload can be checked without having to press the flange on and off and tools for removing and installing the flange.
DiffTools.jpg
Click to expand...
Wow .. where did you find all these ? Very impressive collection !

Is it ok to take some accurate measurements (if you got calipers) and photos for me ? Here is what i would like to have:

  1. Tool 2685: one close/detailed photo on each side (front and rear) and one on the side. Also measure the (minimum) thickness of the tool when the inner ring is bolted all the way in and the (maximum) thickness of the tool when the inner ring is at its maximum/highest setting. In this way we could find out the height range of the tool, ie how much it can raise the pinion. If possible since i can see that one side is sloped, maybe the lowest and highest point of the slope (with the inner ring all the way screwed in).
  2. Tool 2841: a photo to see how it is designed from the side that the sticker is. Does it have threads in it or just these two "teeth" only and is a hollow pipe ? Also please measure its total length to have an idea of how long it is.
  3. Tool 2595: one close/detailed photo on each side (front and rear) and one on the side. Also the minimum thickness of the tool when the rings are in their closest setting and one when the rings are the furthest possible. Outer diameter should be the same as the bearings as mentioned before, but maybe we could take a measuremet as well.
  4. Tool 2600: Some photos as well. As for measurements, the thickness of the upper plate and the distance between the 2 plates (as far as i understand the distance is fixed).
  5. Tool 2393: Take some general photos, but the most important is to have very accurate measuremets. Can you please measure the height of spacer B (look in the first thread) and the thickness of the shaft at zeroing point "2"
I think if these are enough to see how the tools are designed and if they are based on Dana 30 theoretical dimensions.
 
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It took years of collecting. I bought some from other shops that didn't work on the older cars anymore and some from ebay.

I'll try to get the measurements and pics for you.
 
Nice writeup! A full collection of drawings would be awesome.
You can easily decide which diff you have. 1030 have a normal constant inner flange shape of the diff cover mating surface. 1031 has two thinner sections to clear the bigger ring gear.

I think case spreader and the bearing removal tools are a must. The others can be really handy, especially in series production/service, but not necessary for the one time diff job.
You can convert standard bearings to testbearings - slip fit, with a bit of grinding. That is enough for 'quick' setup of the shims, and for quicker trial and error setup of the contact pattern.

That gear whine sounds like a more matured version of my new 3.08's noise. I still need to do some investigation, but i think i drove mine too hard early in in the breakin process.
If you don't want to end up with the same noise again, somehow source a low mile full axle with the correct ratio, and just install the new diff carrier with new seals. (at least brownie has zero noise with this method)

Grinding noise could be M90 design & single mass flywheel related. My friend has ugly grinding noise on decel with his setup too, which became worse after a light KLRacing flywheel.
 
petiww said:
Nice writeup! A full collection of drawings would be awesome.
You can easily decide which diff you have. 1030 have a normal constant inner flange shape of the diff cover mating surface. 1031 has two thinner sections to clear the bigger ring gear.

I think case spreader and the bearing removal tools are a must. The others can be really handy, especially in series production/service, but not necessary for the one time diff job.
You can convert standard bearings to testbearings - slip fit, with a bit of grinding. That is enough for 'quick' setup of the shims, and for quicker trial and error setup of the contact pattern.

That gear whine sounds like a more matured version of my new 3.08's noise. I still need to do some investigation, but i think i drove mine too hard early in in the breakin process.
If you don't want to end up with the same noise again, somehow source a low mile full axle with the correct ratio, and just install the new diff carrier with new seals. (at least brownie has zero noise with this method)

Grinding noise could be M90 design & single mass flywheel related. My friend has ugly grinding noise on decel with his setup too, which became worse after a light KLRacing flywheel.
Click to expand...

Yeah case spreader is a good tool. I had made one myself back then from scrap metals, to change the stock diff to the TrueTrac. Doesn't need to be elegant but to just work .. lol

The only pic i got from my diff is the first one in post #2 in my thread https://turbobricks.com/index.php?t...hopefully-fast-240-brick.310632/#post-5190268
I think that 1030s don't have this upper cutout for the ring gear (maybe this is what you are referring to). Can you identify something there ?

As for the grinding noise .. i changed a dog dish flywheel to a bakaxel.se flywheel/765 combo which really doesn't have too much weight difference due to its size. I would swear that the noise is heard from the rear of the car .. but again .. no idea !

I took apart the M90 for this reason and replaced most of its bearings and also cleaned it. Found nothing weird in there, this story is described in my thread as well ! There are not many things to take apart anymore other than the diff.. lol
 
According to my tool inventory, I still have the majority of these tools boxed in the basement. I wouldn't be surprised if guys have been using them as generic press tools.

If Hiper doesn't have one or can't get measurements, let me know. I'll see what I can find time to measure for you.

Jordan
 
I made a pinion depth tool using some flat ground material and placing it on the carrier bearing split. Compensate for the thickness of the ground flat bar, and you have your pinion depth.

If you follow the Dana rebuild procedure vs the volvo one, it's a bit less confusing and works well with setup bearings. It gets you into the ballpark, but I always end up tweaking things 0.005in or so to make the pattern what I want. Still a lot faster than the guess and check method.
 
culberro said:
I made a pinion depth tool using some flat ground material and placing it on the carrier bearing split. Compensate for the thickness of the ground flat bar, and you have your pinion depth.

If you follow the Dana rebuild procedure vs the volvo one, it's a bit less confusing and works well with setup bearings. It gets you into the ballpark, but I always end up tweaking things 0.005in or so to make the pattern what I want. Still a lot faster than the guess and check method.
Click to expand...

I was wondering, is there a manual or something for Dana procedure ?

The main thought initially was to see if the Dana 30 measurements (mainly NPD 2,250" / 57,15mm) applies to 1031 style differentials as well, which looks that it does. This could only be done by measuring the dimensions of the original tools. The guy from Jeepforums link that i shared above has made some nice tools as well, much easier fabricated than the original Volvo tool. He has a similar methodology to the Volvo pinion depth tool design. However apart from "being sure" about everything before starting the diff job, it would be nice to make it fast and accurate. Set up bearings for example are a very nice idea which works but takes much more time to set up as mentioned above. That said, it doesn't mean that i wouldn't use it and cut down the expenses of that job !!

By the way some say (i don't remember where i read it) that the bearing split point (if i understand correctly it is the point at where the bearing caps mate with the diff's case) is not the centerline of the axle. I don't know if this is correct, but what i think is not important, i would prefer to measure that somehow or find some documentation that mentions it (which i doubt). I wonder however why did Volvo do it that much complicated ? This way sounds much more easier ..
 
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GTJordan said:
According to my tool inventory, I still have the majority of these tools boxed in the basement. I wouldn't be surprised if guys have been using them as generic press tools.

If Hiper doesn't have one or can't get measurements, let me know. I'll see what I can find time to measure for you.

Jordan
Click to expand...

Ah .. you are one of the lucky people as well then !! I am really not sure if there ever was such a tool present Greece ... :cry:

Anyway, it is always nice to have a backup plan ! Thanks !
 
Over the years I have made setup bearings for many of the diff's that I have rebuilt 8+.
Also you need an inch pound torque wrench.
 
culberro said:
Here is the Dana 30 rebuild manual on google drive, because it's too big to host here.

Dana Spicer Model 30 Repair Manual.pdf

drive.google.com drive.google.com
Click to expand...
Thanks for posting this manual. It looks that the procedure described in there is the same that the post in Jeepforum is following with lots of pics. It looks simpler than Volvo's procedure and with less tools !!
 
aristg said:
Thanks for posting this manual. It looks that the procedure described in there is the same that the post in Jeepforum is following with lots of pics. It looks simpler than Volvo's procedure and with less tools !!
Click to expand...
That's what I found as well.

The Dana procedure is a bit odd and you have to be careful and consistent with your measurements. The upside is that it requires only a dial indicator with a mag-base, and setup bearings.
 
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