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Discussion Starter #1 (Edited)
Short story and I'll get on with it. Last week at the tail end of a snow storm, I managed to snap the right front axle at its relief score line near the inner cv just inside the boot. Basically wrenched the axle in low range. No drive, reverse or park in high or low range without locking the center diff. Center diff locked gave me rear drive in low range enough to get the last block home.

Replaced the right front axle with an new VW axle assembly yesterday. Now it romps around like it used to, but now has the slightest whine from the right front only on deceleration and is most audible speed specific from 65 down to 35mph. No vibration, binding, or other alarming noises. I could have brindled or pushed an already aged out flange bearing over the edge.

At 98,800 Miles on this V8 I'm sure it's the front differential being over stressed in the snow storm. It already has a new prop shaft center bearing and it's not the front wheel bearings.

My specific questions

1) Has anyone replaced just the flange bearings alone and it resolved a noisy front differential?

2) Has anyone also had an issue with a pinion bearing on a front differential also?

3) Does anyone have pics of a disassembled front diff or one with flanges removed? I did find some pics of a rear diff on this forum.

4) Can the left extension housing be removed and the diff removed without taking too much apart? Can you get enough lift on the engine to get the diff out with the subframe still in place?

5) Is it possible to buy the differential itself (the internal part) and what are some part numbers to research?

While this post is bouncing around, I'm going down to check play on the flanges and input shaft while it's warm and post back. Thanks!
 

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Discussion Starter #3

After a day of carefully pinpointing the noise I'm hearing, it is definitely in the front differential.

In the attached video, I had all 4 wheels off the ground in park. I grabbed one rear wheel and rotated it to see if I had any excessive slack in the driveline from the t case back. Nothing to note. When I did the same for the front, I found the hollow metallic deceleration noise I've been hearing. There is something stressed, stretched or really worn out in the front diff.

I contacted ZF directly today with an inquiry about parts, hopefully responding soon with a positive answer.

After research all over the web, I was able to verify my diff part number 0AA 409 508H with the letter code JTK. IF I can confirm its a 4,3 ratio, the equivalent diff in Porsche is 955 349 010 21 with the JTJ letter code and it's less expensive than VW new. Audi uses the same diff in the Q7 as the Touareg in this instance.

2007-2010 is the range where my diff ratios are used. No 4,3 ratios used before 2007, so finding used ones are a challenge, but there are a few Porsche equivalents out there.

I will post a list of Porsche equivalents (front and rear) with ratios and part numbers shortly.

I would love to find out what differential is used that may be common in some other VW, Audi or Porsche, or be able to find the Spider Gears and Pins, pinion and crown ring, shims and bearings. Someone here did post the Timiken equivalent conical bearings, but I will need a pinion bearing also.

I really don't want to tear into it unless I can find spare parts or a donor diff.

Anyone know where internals can be found?
 

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I disassembled a front diff a month ago to look for a lsd diff.
I'll try to post some pics today ;-)

Can you disconnect the driveshaft? Maybe its the chain in your transfer case that makes such noise. The sound is very 'hollow' for a small front diff case.
With an endoscope you can check trough the oil fill hole if there is a wear pattern on your pinion gear or crown gear. Drain the diff oil to check if there are metal parts in it.

If your crown gear and pinion gear doesn't have signs of wear, you can change the bearings. But it's a precise job to do because off the pinion, crown clearance.
 

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Discussion Starter #6
Alex, thanks, I looked at that document and that is fine for 2006 and down, I would need a FVZ letter code. That document is a great start for gear ratio differences. 2007-2010 VW I would need a letter code JTK. Audi started using the 4,3 ratio Diff in the Q7 in 2006. Porsche started using the 4,3 ratio letter code JTJ in 2007 and I have found a Porsche one that would work.

The codes, part numbers and serial numbers are stamped into the cases (as per your document) near the drain plug. I wish people selling these things knew that, it would help them sell more of them.

B.V., pics would be great posted or PM. The propshaft from the transfer case was disconnected at the transfer case end when I took the vid. I took the entire t-case shaft off and both CVs to isolate the front diff and tried again, no play in the pinion or the axle flanges, but there is a lot of slop within the diff. I've seen conical bearings on each side of the diff wear out on Mercedes ML and RL making the whole diff jump around and I'm hoping that's what it is. Benz owners are having similar issues too.

If I hold the left axle flange and turn the right and put a load on the diff and let go, it feels like the diff drops inside the case (heavy clunk) and makes that hollow ringing sound. Holding both axle flanges and turning the pinion, very little play in engagement, but it's like the ring gear is walking up the pinion gear in one direction.

I have less than 30 miles on it since the axle was replaced and the problem appeared, so hopefully the ring and pinion are ok. I will look into the Timiken bearings today. I am about to get into the transfer case.
 

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Discussion Starter #7
I'm going ahead and will take a chance on repairing my front diff conical bearing. After days of research here on this forum and others coupled with a bit of experience, I feel brave enough to try.

Timiken bearings LM503349 and Timiken Races LM503310 have been ordered, and the seals from VW. I will be disassembling the front differential this upcoming weekend. I would love to have pics to study from anyone that has taken one apart, before I get into mine.

I will do my best to document the entire job including vids and photos and post them here. If I can get any part numbers off the internal diff or other parts to cross reference parts to another source, I will post them too.

Thanks to all that have relayed helpful information thus far.
 

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I quickly made some pics, bad resolution, it was already dark (don't watch the messy table ;-) )






On the first pic, you see all components inside the diff.
The diff carrier is held in place by the Timken bearings, supported by 2 shims.
The thickness of the shims determines the tension on the bearings and the clearance of the pinion gear and crown gear. But if the gears are in good shape, you can reuse them.
I work in a tractor garage and almost all diff clearances are between 0.15mm and 0.3mm, measured on the crown gear.

On the 2nd pic, the original Timken bearing 503349.
I hope you find all parts because it's not easy as they are not OEM Volkswagen.
I looked for a lsd diff lock but i can't find it...

3rd: A try to show the bearing housing.

The diff is not that difficult but the clearance and tension on the conical couple is very important.
If your bearings have to much tension, they will wear to early and cause friction (consumption) -> to less tension, diff can wobble around, gears and bearing will wear.
If the clearance is not good, you will have a whining noise.

Sorry for my bad dutch <-> English technical terms, if you don't understand it, let me know ;-)
 

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Discussion Starter #9 (Edited)
B.V. Thank you. Just curious, did you have to replace your spider gears, if so, are they common to other differentials that have available spare parts? Is the differential a standard of sorts?

What were the torque specs used to reassemble the case bolts?
 

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I did'nt replaced anything yet because it's a spare part (from a damaged touareg)
I thought that the spider gears are all the same (not sure). The diff will probably be not a standard i think.
 

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Discussion Starter #11
B.V. If you still have easy access to the parts, please count the splines on the right flange or left axle. That will give us enough information to find the right spider gears. Spider gears for open front differentials like ours come in different spline counts which dictates their diameter. Open diff spider gears appear to have a standard set of dimensions, what is different are the pins they ride on. It appears we have the type of pin that has one locating hold drilled in one end, secured by a special bolt.

On the crown ring (ring gear) there are numbers normally stamped in the edge. The numbers include the ratio of that ring gear, (i.e 4-3 or 4:3 or 4.3 etc) a part number and sometimes a country of origin or manufacturer.

There may be a number stamped in the end of the pinion shaft, or on the edge near the pinion bearing.

With this information, I may have enough to round up 70% of the differential parts we need or all of it.

Based on the pics, you have a 10 tooth pinion gear, so the crown gear is going to be a 37 tooth gear for a 3.7 ratio, 41 tooth for a 4.1 ratio or a 43 tooth for a 4.3 ratio.

Last thing I'm researching now is how common or proprietary are the pinion gears.

Thanks again for your help.
 

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Hi, have you performed this type of work before? Are you planning on re-using the crown and pinion gears?

If so, before disassembly, check your hear pattern and measure the gear backlash.

Also, see if you can find a measurement for what is called nominal dimension.

I am interested to see what else was damaged due to the shock load that broke the shaft.
 

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Discussion Starter #14
I have done this kind of work before for Mercedes-Benz when the ML first came out. We had a few early ML430s that were eating front diffs. I do have a Mechanical Engineering background and I'm stepping up to make a serious attempt at finding a solution or alternative parts.

I've never had to source parts from scratch like this before. It is definitely a challenge.

If my crown and pinion are in good shape and are reusable, I will measure the backlash and check the gear meshing using a marking compound and adjust carrier bearing shims as necessary, if I can't find the exact dimensions.

I do have a dial micrometer and other precision measuring equipment to give me the best shot I can have with what i have to work with.

Once I determine the deck height on the differential carrier that is in this case, and how many bolts (8-10-12) necessary to mount the ring gear, the thickness, bevel cut direction and diameter of the gear, it will help narrow down my search for replacement parts.

One way to measure Deck Height: http://www.differentials.com/technical-help/carrier-breaks
The other way is to measure from the deck to the lip where the bearing rests.
 

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Others on this board have posted that the bearings appear to be the same as a Ford 9" axle.

I'm interested in your findings as I found similar, but not quite as pronounced, noise with my front differential this evening when changing fluids. Mine has had a slight whine on acceleration around 40-55mph since I purchased it 10k miles ago. It hasn't developed further though...
 

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Hi, on that chart I don't see a reference to nominal dimension. Simply put, this is a measurement from the centreline of the differential carrier to the end of the pinion shaft.

When you did the Mercedes diffs, did you ever check this dimension?

Setting the initial nominal dimension for the pinion shaft gives you an excellent starting point for adjusting pattern and gear backlash. Especially when starting with new crown and pinion gears.
 

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Discussion Starter #17 (Edited)
What I have found at the moment, ring gears and pinion sets are machined to work together and they have a fixed position axially within most differential cases. Backlash measurements are usually between .006" and .010" measured with a dial indicator.

If you have a matched set of a ring gear and pinion, they will be the correct dimensions to mesh together, backlash adjusted by the shims on the pinion and carrier bearings.

If your shims are not damaged, you can reuse them where you had them and your original tolerances should be within range or need to be adjusted with a thicker or thinner shim.

Ring gears are machined on their faces and are usually the same thickness regardless of number of teeth when designed to work with a particular pinion (9, 10, 11 tooth, etc). The ring gear diameter is based on application. Pinions on the other hand are machined on the edge, where the number of teeth determine the diameter of the pinion.

More teeth on the pinion = larger diameter, the matching ring gear will be a little thinner. Less teeth on the pinion = smaller diameter, the matching ring gear will be a little thicker.

If you are custom matching ring gears and pinions for drag racing or rock crawling, in those exceptions is where you run into the need of thicker ring gears or "higher" differential carrier offsets. In our case those special gears and differential carriers are not necessary. I don't think most of us are planning on tearing down a drag strip or rock crawling.

Update: I believe the Ford based 8.8" (Not 9", there is a difference on pinions and ring gear diameter) ring gear and pinion sets will be what's compatible with our differentials. The Ring Gear is a 10 hole design, spans all of the final drive ratios of our Touaregs, Q7s and Cayennes from 2004-2014, initially appears to be dimensionally equivalent (will confirm shortly) and should work with our existing differential carrier. If the Ford based 8.8" sets are the ones that will work, then I will have the spider gears, pinion bearing, crush ring and shims sorted out and we can start completely rebuilding our differentials!

The Timiken carrier bearing is part number LM503349
The Timiken carrier bearing race is part number LM503310
Both are common on many differential carriers 8-9"

I feel the two Timiken bearings and races above were replaced alone, it would solve most of our issues if caught early. I'm going for worst case scenario rebuild info.

The Ford 8.8" are in F-150s, Rangers and Mustangs, a heck of a lot more access to parts.

Thanks for the help everyone.
 

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Great update and info on speculation provided for the Ford parts!
 

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Discussion Starter #19
Good Reading Material for dimensions

Thick Gears vs. Thin Gears and Axle Carrier Breaks Explained

if anyone has a diff apart already and can accurately measure the ring gear diameter, I just want to confirm the measurements.

in the 10 bolt ring gear families:

8.5" to 8.6" I'm leaning towards GM
8.75" I'm leaning towards Chrysler
8.8" I'm leaning towards Ford (which is where I'm guessing at the moment) 223.52mm
9.0" I'm leaning towards Ford

Tenths of an inch will determine which direction to go. I wasn't able to find any local auto parts stores that carried my ratio of 4.30, however most other ratios we need are out there in the Ford 8.8" diameter, most are special order and not in stock.

What is frustrating is the lack of availability of these components in general, locally and worldwide across the internet. Do we manufacture anything in THIS country anymore??? I've talked to machinists, some say they can't reproduce parts out of fear of patent infringement and the low run numbers would be expensive if they did. I talked to ZF, Spicer, Dana, Borg Warner and they have non-compete clauses in their contracts with OEM auto manufacturers which bars them, or their vendors, from selling the components under their own name.

Some OEM Engineers that I know have told me there are only a few manufacturers out there that make these components and dimensions and gear design are common even in european models. They tell me to get the best measurements I can from what we have and compare them to what is available on the market. They say the chances are good that I will find a match piece by piece.

I'm doing my best to help, but there are a lot of closed doors out there including back doors and its surprising and absolutely frustrating.


---------Deleted Rant-------------

It's been that kind of day, lol.
 

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I'd say you've given more info than has been available before. A lot of us either don't have the resources or know how on where to look for this stuff even if the desire is there.
 
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