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Discussion Starter #1
I have a 2006 Touareg 3.2 with 110k. I'm pretty sure the front differential is eating itself up (based on the noise and ultra metallic oil that I recently drained out of it); I've read all the pertaining threads and am pretty sure it's the the differential carrier or pinion bearings, etc. it's definitely not the needle bearings at the end of the support tubes as I have already changed them out.

Anyways, my diff is a 0AA409507H-GNM and according to the pdf found on the first page in the below linked thread... I have 4.56 final drive. I have been researching my options and have found that the Q7 front diff used in 2007-2012 (I believe) 3.6 variants having P/N 0AA409508Q-JMU. This unit also has 4.56 gear ratio and as far as I can tell uses the same prop shaft and axle flanges. I determined this by checking that the prop shaft and axles used in my '06 treg are also used in Q7's having the 0AA409508Q-JMU diff. Also, I'm pretty sure that a variant of the 0AA409508 is listed as the replacement for my 0AA409507H.

My question is... Can anyone think of a reason why I wouldn't be able to use a 0AA409508Q-JMU in my Touareg? These diffs seem to be relatively abundant at lower price with lower miles... So it seems like a good option.

http://www.clubtouareg.com/forums/f95/extremely-specific-front-diff-questions-130018-3.html#/forumsite/20553/topics/130018?page=1




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I'm gonna guess no. Your Touareg has low range--- the Q7 never has had a low range option.
 

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I'm gonna guess no. Your Touareg has low range--- the Q7 never has had a low range option.
low range comes from the transfer case. Not the front differential.

If the ratio is the same you can use it if the casing is the same (which it probably is).
 

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I'm aware of that, but I'm guessing the diffs on the T are beefed up on the first gen models because of their off road capability.
 

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As long as the ratio is the same (VERY important!) and all the parts that hook up to it fit, you should be fine.

I don't see VW having different housings/bearings, etc for models with low range. That creates a logistical nightmare as far as sourcing parts and stocking them.

It all depends on how much the OP is willing to risk buying a used unit that may or may not work..... :- /
 

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Discussion Starter #6
FSJ, I agree with you, I can't see how the internals or housing would be different between the q7 variant and the treg.

The final drive for these q7 3.6's is listed at 4.56 which is the same as my '06 3.2...

Are there any sensors or anything that might differ between the q7 diff and the Touareg diff?

So my plan would be to source a reasonably priced used q7 diff making sure it came from a vehicle that has been in an accident... And not being parted for mechanical issues, inspect, possibly rebuild or have someone do it for me (if it needs it), then swap out that diff for mine. This strategy is in the interest of having my treg down for repair the least amount of time.


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Sorry, I wouldn't have a clue on the sensors, etc. I'm sure there are some somewhere. LOL!

I was poking around VCDS yesterday and discovered that one of the measuring blocks for my TRANSFER CASE actually showed what % of load the t-case was under. And yes, it displayed a front and rear % separately.
 

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Remember the final drive isn't as important in terms of the front diff as the center differential transfer gearing. You might have a 4.56 final drive and rear diff and a 1:1.1 center transfer. The spline count may also change between years (very common).

Don't know if any of this is common knowledge, so you almost need to see them side by side, check the markings, and count the splines.
 

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Discussion Starter #9
Update... Just stopped by my local VW dealership and talked to the parts folks... Was able to confirm that the two front differentials in question share the same axle half shafts and prop shaft flange. This confirms that the spline count is exactly the same and probably that the spider gears and differential is the same too...


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Discussion Starter #10
Any other ideas. I don't think there are any sensors on the differentials. I've found that the bushings that are installed in the differentials (rubber bushings that mount the differential to frame/subframe) have different part numbers, but the fasteners are the same...


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Maybe the bushings have different a stiffness? Perhaps one version is stiffer than another? Although I can't see how they'd decide who got the softer ride? :- p
 

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Discussion Starter #12
Ya, I'm not really worried about the bushings... I think I will go ahead and source a q7 diff and compare.

Here's an interesting fact... I just talked to my local LKQ auto recycler... A used 0aa409507h (Touareg) will run $1200... The 0aa409508q (q7) will cost $375...


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Thank you. Please keep us updated.

I am sure that several of us are waiting with fingers crossed, hoping that this works out for you.

Don't forget... we love pictures too. lol. :D
 

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Discussion Starter #14
There will be pictures... I purchased a used 0aa409508q from LKQ today and I'll pick it up tomorrow.

I'm thinking I will try and swap the differentials this weekend. I figure I'd get the part tomorrow and inspect it for any red flags (indicating non interchangeability)... Does anyone know how easy it is to open one of these up? Is there a cover? Are there gaskets or are they just sealed with rtf?


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Discussion Starter #15
I picked up my Q7 diff today and it looks great... $375, got it within one day of ordering, 63k on the part, it's the right part number, exactly what I was expecting (except it didn't come with axels, good thing these are interchangeable with the Touareg ones).

It's crazy though that VW charges $4k for this thing new. It literally weighs about 40lb... I didn't even have to fold the seats down in my A4.

Does anyone know what size the subframe bolts are in the Touareg (thread diameter and pitch)? I was thinking I would take the subframe bolts out one at a time and replace with all-thread and nuts, then lower the subframe down by backing the nuts off individually. Seems like it would be easier and more stable than using a jack or something.


 

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From the other thread, removing the long end of the axle housing can release one of the thrust bearings that help set the gear backlash. So be careful if you remove it.

Otherwise, once that's off, it looks like you can pull the rear cover off for inspection.

Or just change oil and run it!
 

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Discussion Starter #17
Ladies and gentlemen, today was a true test determination and upper body strength... And it was totally worth it. The Touareg is back on the road with the 0aa409508q and it's quiet and smooth... So chalk up another 0aa409507h failure. As far as I can tell, the carrier bearings are shot, I'll have to do an autopsy at a later date to tell for sure.

As far as I can tell, the two differentials are identical... The bushings are indeed slightly different, but their fitment is identical. Internals may be different somehow, but the gear ratio is indeed identical. If I have any problems with it I'll post but otherwise, I'd suggest going the q7 diff route. I got mine from an local auto recycler for $375, but there are some on eBay for $320 with free shipping.

Based on what I've read about the differentials in T1's (like my 0aa409507h), there seems to be something inherently wrong with the part (which makes since sense the 0aa409507h was replaced by the 0aa409508k in 2006). Though it is possible that the inherent problem could be with the initial setup of the differential/pinion/bearings, it could also be a design error which means that it may not be worth rebuilding, but replacing with a later revision differential. Those of you that have rebuilt their differentials, how long have you been running since the rebuild? Any problems?







 

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I've got a v8 so it looks like I need a different differential. I think mine is a 4.1:1 ratio but have to confirm by looking at the differential.
 
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