Below you can find all relevant information I've gathered about the transmission, transfer case, front and rear differential fluid change procedures in the last few weeks. I'm posting this compilation here for convenience and easier discovery for others who are interested in doing these, or at least in learning about them.
Automatic transmission fluid change
Automatic transmission units are the same in all first generation Touaregs. They're an Aisin Warner (AW) TR-60SN 09D, 6-speed unit. Servicing consists of replacing the oil filter, changing the oil, and replacing some gaskets and bolts. The full transmission maintenance service set consists of the following parts:
09D 325 435 - transmission filter (thinner), 1 piece
WHT 000 322 - transmission filter bolt, 3 pieces
09D 325 443 - transmission filter gasket, 1 piece
09D 321 371 - transmission oil sump gasket, 1 piece
WHT 000 326 A - transmission pan bolts (M6X25), 16 pieces
WHT 000 206 A - transmission fill plug (M10x9), 1 piece
09D 321 181 B - transmission fill plug washer, 1 piece
WHT 000 323 A - transmission drain plug (M24X1.5), 1 piece
09D 321 379 - transmission drain plus washer, 1 piece
G 055 025 A2 - transmission fluid, 9-12 liters (depending on drain level)
Additional to these you may opt to replace also the transmission oil temperature valve (ie. thermostat), as a precaution, to avoid possible overheating of the transmission oil:
7L0 317 027 A - temperature valve, 1 piece
N 906 660 03 - o-ring, 4 pieces
Transfer case fluid change
Transfer cases are generally the same in every first generation Touareg. (Actually, there are technical differences between them, but these do not affect the fluid change procedure). They also works as the central differential unit, which is using an electronically controlled locking mechanism. The transfer case is part of the transmission unit, but has a separate designation: 0AD. Servicing the transfer case consists of changing the fluid and replacing the drain and fill plug bolts. Full service set consists of:
0AD 301 115 A - transfer case fill & drain plug (17.5x12), 2 pieces
G 055 515 A2 - transfer case fluid, 0.85 liters (also known as G 052 515 A2, previously G 055 015 A2)
Differentials fluid change
There are two separate differentials in 1st gen Touaregs (besides the integrated central one, see above, which however is not a separate unit). Both the front and the rear differentials might be a "locking" or a "non-locking" one. Locking differentials need different fluids than the non-locking ones, because of the clutches in them, which need to "stick" when engaged.
Whether the front or rear differential is locking can be determined by looking at the differential control switch in the center console. If a differential can be locked, there's a thick dot at the specific point/"joint" representing the differential on the schematic drawing of the running gear. Alternatively you can look at the build sticker (found in the owner's manual and next to the spare wheel) and look for codes: 1Y0 (both front and rear diffs are non-locking), 1Y1 (non-locking front, locking back diff) and 1Y2 (both front and rear diffs are lockable) to determine which differentials are lockable. Touaregs with locking front diffs are very rare, but most higher trim models have locking rear diffs. Base models' only lockable differential is the center one, and the rear and front differentials are non-lockable.
All differentials need the following bolts replaced during service:
0AA 409 057 - differential fill & drain plug (M16x1.5), 2 pieces / differential
Non-locking differential service fluid:
G 052 145 S2 - non-locking differential fluid 75W-90 (also known as G 052 145 A2 and G 052 145 A1)
Locking differential service fluid:
G 052 196 A2 - locking differential fluid 75W-85 with limited slip
Fluid volumes:
Front differentials take usually about 1.0-1.2 liters of fluid (depending on whether they're locking), while rear differentials take take around 1.6 liters of fluid. However, depending on the effectivity and completeness of your drain, the amount of fluid you can actually put in them might be slightly less.
Fluid change procedures
The fluid change procedure for automatic transmission, transfer case and differentials is described in the Touareg workshop manuals. Even though the procedures (especially for the differentials) are fairly simple, they must be followed exactly to avoid damage. The services manuals are downloadable from Volkswagen's official ErWin page. You'll need to pay for a (limited-time) "subscription" to access the manuals, but this will only cost a few bucks, and will allow you to download all the manuals at once. I suggest you do that (ie. download all manuals), so, you can browse them later any time you need.
The transmission fluid change procedure is described in "Automatic gearbox 09D" workshop manual (K0058960920-Automatic_gearbox_09D.pdf). To complete the procedure you'll also need a VAG-COM diagnostic device that will allow you to keep an eye on the transmission fluid temperature. Without that you won't be able to fill the right amount of fluid into the transmission, which might result in permanent damage to the unit.
The transfer case, and front/rear differential fluid change procedures are described in "Transfer box and final drive" workshop manual (K0058960720-Transfer_box_and_final_drive.pdf). No VAG-COM device will be needed for these.
Alternatively/additionally you might find useful information on these subject also in the following forum threads. I suggest you have a look at these even if you will be using the official service manuals, because they contain a lot of pictures which help identify parts and get a general idea of the replacement procedure. So, the threads are:
DIY TRANSMISSION FLUID CHANGE pics
ATF
Diff oil and Transfer Case oil change
Transmission Fluid Change Dealer Quotes, and Dilemma
Automatic transmission in the Touareg (typical problems needed consumables) (Russian)
Replacing the engine oil, box, differentials and transfer case (Russian)
Fluid change intervals
Volkswagen itself makes no mention at what intervals you're supposed to change the transmission/differential fluids, and actually claims these boxes to be "lifetime fills" or "sealed for life". However, "lifetime" in this context only means "for the duration of the warranty period", and depending on how you're using your car, you might want to replace the fluids sooner or later. Opinions differ on when this should be or is ideal, but the Porsche Cayenne's technical manual (which car is using essentially the same drivetrain as the Touareg and is using the same Aisin 09D auto transmission) advises to replace the fluids after 16 years or 240.000 kms / 160.000 miles. However, if you're towing, off-roading, driving on mountain roads frequently or living in a very cold climate, the wear and tear increases on these parts, and because of that you might want to change fluids more frequently.
General remarks regarding fluid changes
Bolts and gaskets might be reused after cleaning, but this is not recommended. Failure to renew these might lead to leaks, or in the case of the transmission filter also to transmission malfunction.
When filling the transmission fluid it's essential for the box to have the specified 35°C / 95°F temperature, otherwise the level will be off, and shifting problems/damage to the transmission might arise.
Always start fluid changes by removing the fill plugs/bolts first, because sometimes they will be seized and/or you will not be able to remove them without additional tools and/or some penetrator fluid. Now, if you only notice that after you've removed the drain bolt and drained the fluid, you won't be able to drive the car anymore to get more tools or take it to a shop.
"Aftermarket" / 3rd party fluids
Instead of the original Volkswagen fluids, several other 3rd party or aftermarket fluids can be used that meet the same specs, but cost a fraction of the original fluids. However, always make sure that the fluid you're using is not only the same viscosity, but also actually conforms to the specific G XXX XXX XXX tolerances listed above! Failure to do so might lead to shortened lifespan or possibly fatal damage to the serviced units/differentials.
Some people (and of course also VW/dealerships) flat out advise against using any 3rd party fluids, while others are using them without any problems for several tens of thousands of kms/miles. However, during my research into this I've found no instances where people used an alternative fluid meeting appropriate specs instead of the original one, and encountered any problems because of that. There were a few cases where people had issues after a transmission flush, but in every single case (at least in the ones I read about) this turned out to be either because they used a wrong fluid to being with, or because a gasket has been misplaced or crushed.
That said there's no guarantee for anything, and in the end it's up to you who you trust, and whether you're ready to pay the exorbitant prices for original fluids, or rather want to go with some more affordable alternatives.
As of 2019, the following fluids are advertised by their manufacturers as meeting the specs/tolerances of the original VW fluids listed above. (Enclosed in parentheses are the exact designations of the specifications the particular fluid claims to be meeting or exceeding):
G 055 025 A2 (automatic transmission fluid, 9-12 liters needed):
Mobil 1 ATF 3309 ("VW G-055-025-A2", and bottle also has the very same shape and design as the original VW one)
Liqui Moly Top Tec ATF 1200 ("VW G 055 025")
Febi ATF 29934 / 101161 ("VW G 055 025 / G 055 025 A2")
Ravenol T-IV Fluid ("VW/AUDI G 055 025 A2")
Meyle 014 019 2300 ("VW G 055 025")
febi 29934 / SWAG 81 92 9934 / Blue Print ADG05532 ("G 055 025 / G 055 025 A2")
Vaico Automatic Transmission Oil ATF Spezial V60-0208 ("VW/ AUDI: G-052-025-A2 / G-052-162-A1")
Addinol ATF XN PLUS ("VW/Audi G-055-025-A2")
G 055 515 A2 (transfer case fluid, <1 liter needed):
Ravenol Transfer Fluid TF-0870 ("VW G 052 515 A2 / G 055 015 A2" - also explicitly mentions as being compatible and having been tested with the Touareg 09D transmissions)
Rock Oil Gearaxl TF0870 ("VW G 052 515 A2, formerly G 055 015 A2" - also explicitly mentions Touareg 09D transmissions)
G 052 145 A2/S2 (non-locking differential fluid, <2 liters/axle needed):
Fuchs Titan Sintopoid SAE 75W-90 ("VW TL 521 45-Y / G 052 145 A2")
Liqui Moly 4433/4434 (spec sheet only mentions "VW 501 50 (G50)", but confirmed by customer support in email to be compatible with G 052 145 and appropriate for Touaregs)
G 052 196 A2 (locking differential fluid, <2 liters/axle needed):
RAVENOL MDL Multi-Disc locking differentials ("VW G 052 196 A2", explicitly mentions Touareg)
RAVENOL DGL SAE 75W-85 GL-5 LS ("VW G 052 196 A2")
Aftermarket replacement parts
Instead of the original VW parts you might also opt to use aftermarket ones. Aftermarket parts are provided by several manufacturers. The most common/well-known ones are as follows:
09D 325 435 (transmission filter):
Vaico V10-0435
SCT SG1074
Meyle 100 136 0002
Topran 113403
09D 321 371 (oil sump gasket):
Vaico V10-0436
Meyle 100 321 0010 (MMX0470)
Topran 113393
Kits (these come with the filter+gasket, and in some cases even with bolts or fluids included):
Meyle 1001370002/MHK0012
Meyle 1001350105/MOK0017 (also includes transmission fluid)
Topran 115998
Kamoka F600501
-----------------------------------------------------------------------------
Disclaimer: Even though I went out of my way to verify every bit of information here, obviously I can not take any responsibility for them being correct. So, alway make sure to double check everything you read. The transmission and the axles are very expensive parts of your Touareg, so, if you mess up something in them, it will cost you. Better safe than sorry!
Automatic transmission fluid change
Automatic transmission units are the same in all first generation Touaregs. They're an Aisin Warner (AW) TR-60SN 09D, 6-speed unit. Servicing consists of replacing the oil filter, changing the oil, and replacing some gaskets and bolts. The full transmission maintenance service set consists of the following parts:
09D 325 435 - transmission filter (thinner), 1 piece
WHT 000 322 - transmission filter bolt, 3 pieces
09D 325 443 - transmission filter gasket, 1 piece
09D 321 371 - transmission oil sump gasket, 1 piece
WHT 000 326 A - transmission pan bolts (M6X25), 16 pieces
WHT 000 206 A - transmission fill plug (M10x9), 1 piece
09D 321 181 B - transmission fill plug washer, 1 piece
WHT 000 323 A - transmission drain plug (M24X1.5), 1 piece
09D 321 379 - transmission drain plus washer, 1 piece
G 055 025 A2 - transmission fluid, 9-12 liters (depending on drain level)
Additional to these you may opt to replace also the transmission oil temperature valve (ie. thermostat), as a precaution, to avoid possible overheating of the transmission oil:
7L0 317 027 A - temperature valve, 1 piece
N 906 660 03 - o-ring, 4 pieces
Transfer case fluid change
Transfer cases are generally the same in every first generation Touareg. (Actually, there are technical differences between them, but these do not affect the fluid change procedure). They also works as the central differential unit, which is using an electronically controlled locking mechanism. The transfer case is part of the transmission unit, but has a separate designation: 0AD. Servicing the transfer case consists of changing the fluid and replacing the drain and fill plug bolts. Full service set consists of:
0AD 301 115 A - transfer case fill & drain plug (17.5x12), 2 pieces
G 055 515 A2 - transfer case fluid, 0.85 liters (also known as G 052 515 A2, previously G 055 015 A2)
Differentials fluid change
There are two separate differentials in 1st gen Touaregs (besides the integrated central one, see above, which however is not a separate unit). Both the front and the rear differentials might be a "locking" or a "non-locking" one. Locking differentials need different fluids than the non-locking ones, because of the clutches in them, which need to "stick" when engaged.
Whether the front or rear differential is locking can be determined by looking at the differential control switch in the center console. If a differential can be locked, there's a thick dot at the specific point/"joint" representing the differential on the schematic drawing of the running gear. Alternatively you can look at the build sticker (found in the owner's manual and next to the spare wheel) and look for codes: 1Y0 (both front and rear diffs are non-locking), 1Y1 (non-locking front, locking back diff) and 1Y2 (both front and rear diffs are lockable) to determine which differentials are lockable. Touaregs with locking front diffs are very rare, but most higher trim models have locking rear diffs. Base models' only lockable differential is the center one, and the rear and front differentials are non-lockable.
All differentials need the following bolts replaced during service:
0AA 409 057 - differential fill & drain plug (M16x1.5), 2 pieces / differential
Non-locking differential service fluid:
G 052 145 S2 - non-locking differential fluid 75W-90 (also known as G 052 145 A2 and G 052 145 A1)
Locking differential service fluid:
G 052 196 A2 - locking differential fluid 75W-85 with limited slip
Fluid volumes:
Front differentials take usually about 1.0-1.2 liters of fluid (depending on whether they're locking), while rear differentials take take around 1.6 liters of fluid. However, depending on the effectivity and completeness of your drain, the amount of fluid you can actually put in them might be slightly less.
Fluid change procedures
The fluid change procedure for automatic transmission, transfer case and differentials is described in the Touareg workshop manuals. Even though the procedures (especially for the differentials) are fairly simple, they must be followed exactly to avoid damage. The services manuals are downloadable from Volkswagen's official ErWin page. You'll need to pay for a (limited-time) "subscription" to access the manuals, but this will only cost a few bucks, and will allow you to download all the manuals at once. I suggest you do that (ie. download all manuals), so, you can browse them later any time you need.
The transmission fluid change procedure is described in "Automatic gearbox 09D" workshop manual (K0058960920-Automatic_gearbox_09D.pdf). To complete the procedure you'll also need a VAG-COM diagnostic device that will allow you to keep an eye on the transmission fluid temperature. Without that you won't be able to fill the right amount of fluid into the transmission, which might result in permanent damage to the unit.
The transfer case, and front/rear differential fluid change procedures are described in "Transfer box and final drive" workshop manual (K0058960720-Transfer_box_and_final_drive.pdf). No VAG-COM device will be needed for these.
Alternatively/additionally you might find useful information on these subject also in the following forum threads. I suggest you have a look at these even if you will be using the official service manuals, because they contain a lot of pictures which help identify parts and get a general idea of the replacement procedure. So, the threads are:
DIY TRANSMISSION FLUID CHANGE pics
ATFDiff oil and Transfer Case oil change
Transmission Fluid Change Dealer Quotes, and Dilemma
Automatic transmission in the Touareg (typical problems needed consumables) (Russian)
Replacing the engine oil, box, differentials and transfer case (Russian)
Fluid change intervals
Volkswagen itself makes no mention at what intervals you're supposed to change the transmission/differential fluids, and actually claims these boxes to be "lifetime fills" or "sealed for life". However, "lifetime" in this context only means "for the duration of the warranty period", and depending on how you're using your car, you might want to replace the fluids sooner or later. Opinions differ on when this should be or is ideal, but the Porsche Cayenne's technical manual (which car is using essentially the same drivetrain as the Touareg and is using the same Aisin 09D auto transmission) advises to replace the fluids after 16 years or 240.000 kms / 160.000 miles. However, if you're towing, off-roading, driving on mountain roads frequently or living in a very cold climate, the wear and tear increases on these parts, and because of that you might want to change fluids more frequently.
General remarks regarding fluid changes
Bolts and gaskets might be reused after cleaning, but this is not recommended. Failure to renew these might lead to leaks, or in the case of the transmission filter also to transmission malfunction.
When filling the transmission fluid it's essential for the box to have the specified 35°C / 95°F temperature, otherwise the level will be off, and shifting problems/damage to the transmission might arise.
Always start fluid changes by removing the fill plugs/bolts first, because sometimes they will be seized and/or you will not be able to remove them without additional tools and/or some penetrator fluid. Now, if you only notice that after you've removed the drain bolt and drained the fluid, you won't be able to drive the car anymore to get more tools or take it to a shop.
"Aftermarket" / 3rd party fluids
Instead of the original Volkswagen fluids, several other 3rd party or aftermarket fluids can be used that meet the same specs, but cost a fraction of the original fluids. However, always make sure that the fluid you're using is not only the same viscosity, but also actually conforms to the specific G XXX XXX XXX tolerances listed above! Failure to do so might lead to shortened lifespan or possibly fatal damage to the serviced units/differentials.
Some people (and of course also VW/dealerships) flat out advise against using any 3rd party fluids, while others are using them without any problems for several tens of thousands of kms/miles. However, during my research into this I've found no instances where people used an alternative fluid meeting appropriate specs instead of the original one, and encountered any problems because of that. There were a few cases where people had issues after a transmission flush, but in every single case (at least in the ones I read about) this turned out to be either because they used a wrong fluid to being with, or because a gasket has been misplaced or crushed.
That said there's no guarantee for anything, and in the end it's up to you who you trust, and whether you're ready to pay the exorbitant prices for original fluids, or rather want to go with some more affordable alternatives.
As of 2019, the following fluids are advertised by their manufacturers as meeting the specs/tolerances of the original VW fluids listed above. (Enclosed in parentheses are the exact designations of the specifications the particular fluid claims to be meeting or exceeding):
G 055 025 A2 (automatic transmission fluid, 9-12 liters needed):
Mobil 1 ATF 3309 ("VW G-055-025-A2", and bottle also has the very same shape and design as the original VW one)
Liqui Moly Top Tec ATF 1200 ("VW G 055 025")
Febi ATF 29934 / 101161 ("VW G 055 025 / G 055 025 A2")
Ravenol T-IV Fluid ("VW/AUDI G 055 025 A2")
Meyle 014 019 2300 ("VW G 055 025")
febi 29934 / SWAG 81 92 9934 / Blue Print ADG05532 ("G 055 025 / G 055 025 A2")
Vaico Automatic Transmission Oil ATF Spezial V60-0208 ("VW/ AUDI: G-052-025-A2 / G-052-162-A1")
Addinol ATF XN PLUS ("VW/Audi G-055-025-A2")
G 055 515 A2 (transfer case fluid, <1 liter needed):
Ravenol Transfer Fluid TF-0870 ("VW G 052 515 A2 / G 055 015 A2" - also explicitly mentions as being compatible and having been tested with the Touareg 09D transmissions)
Rock Oil Gearaxl TF0870 ("VW G 052 515 A2, formerly G 055 015 A2" - also explicitly mentions Touareg 09D transmissions)
G 052 145 A2/S2 (non-locking differential fluid, <2 liters/axle needed):
Fuchs Titan Sintopoid SAE 75W-90 ("VW TL 521 45-Y / G 052 145 A2")
Liqui Moly 4433/4434 (spec sheet only mentions "VW 501 50 (G50)", but confirmed by customer support in email to be compatible with G 052 145 and appropriate for Touaregs)
G 052 196 A2 (locking differential fluid, <2 liters/axle needed):
RAVENOL MDL Multi-Disc locking differentials ("VW G 052 196 A2", explicitly mentions Touareg)
RAVENOL DGL SAE 75W-85 GL-5 LS ("VW G 052 196 A2")
Aftermarket replacement parts
Instead of the original VW parts you might also opt to use aftermarket ones. Aftermarket parts are provided by several manufacturers. The most common/well-known ones are as follows:
09D 325 435 (transmission filter):
Vaico V10-0435
SCT SG1074
Meyle 100 136 0002
Topran 113403
09D 321 371 (oil sump gasket):
Vaico V10-0436
Meyle 100 321 0010 (MMX0470)
Topran 113393
Kits (these come with the filter+gasket, and in some cases even with bolts or fluids included):
Meyle 1001370002/MHK0012
Meyle 1001350105/MOK0017 (also includes transmission fluid)
Topran 115998
Kamoka F600501
-----------------------------------------------------------------------------
Disclaimer: Even though I went out of my way to verify every bit of information here, obviously I can not take any responsibility for them being correct. So, alway make sure to double check everything you read. The transmission and the axles are very expensive parts of your Touareg, so, if you mess up something in them, it will cost you. Better safe than sorry!
