calling doctor Smac, shorter axles on the sport suspension?

[Spawne32]

I am replacing both my front CV axles and I noticed a part number issue. Option 1BE seems to specify a different part number for the CV axle, 18.11" compressed length vs the standard suspension of 18.17" compressed length. Specifically 8K0-407-271-AJ and 8K0-407-271-P. Curiosity got the better of me as to why they would have a slightly shorter axle for the sport suspension, as I had assumed you wanted a longer axle for a lower ride height, assuming that is the reason for that change.

[fastboatster]

I am no Smac, but I believe AJ axles are for fwd A4 2.0 and for b8 s4 and s5 with 3.0 and 4.2. P axles are for awd A4. Was looking for the front axles myself and this is what I found on https://parts.audiusa.com/p/Audi__A4...0407271AJ.html notice it says “ 2.0 LITER, w/o AWD”

[Spawne32]

I am no Smac, but I believe AJ axles are for fwd A4 2.0 and for b8 s4 and s5 with 3.0 and 4.2. P axles are for awd A4. Was looking for the front axles myself and this is what I found on https://parts.audiusa.com/p/Audi__A4...0407271AJ.html notice it says “ 2.0 LITER, w/o AWD”

Interesting thing about that is if you pull down the little menu there, it does show quattro vehicles as compatible, including the S5, S4, and RS5 models. Trakmotive lists two axles in their catalog, one for standard suspension, and then this shorter one for 1BE cars (sport suspension or heavy duty suspension) which seems to cross reference back to this different axle. However I am still confused by the two lengths.

[bb-tt]

I think Smac should have his own thread here. Be easier to find all his answers LOL.

[alhutch]

ETKA says 271 P is correct for your car. That part number runs until it was revved to 271 Q after production date 11/7/2011. Not sure how 271 AJ got into the mix, as ETKA shows that is for later 6 cylinder AWD & front drive 4 cylinder cars. 271 AL is the correct axle for B8.5 4 cylinder AWD.

Seems unlikely Audi would spec a different length axle for something as mundane as a shorter spring.

[Smac770]

Hahaha. Maybe if AZ wants to give me a booth like Lucy on Peanuts, and throw me some peanuts. :-P

B8 uses three GKN built options:

Peened triple roller joint AAR 2600 i with an outer CV joint with an 85/88 mm diameter.
Peened triple roller joint AAR 3300 i with an outer CV joint with an 94/100 mm diameter.
Peened triple roller joint AAR 3300 i with an outer CV joint with an 99/106 mm diameter.

It very well could be the 2600 vs 3300 refers to a difference in length of the triple roller sleeve, but I believe it's more about input strength and durability.

While I see the variation of rev R over the standard rev Q for suspension 1BR (rough roads, lifted suspension) with certain engines, I don't see any such variance for the sport suspensions. Both Q and R are just AJ now. S when to AK. It seems like P became AL, but didn't "roll" to AL. P is still the rev for B8.0 quattro 2.0T.

So I suspect the R used a beefier outer CV (that was the part that differed between Q and R) and they just consolidated that variance into a single AJ.

[Spawne32]

See I knew I could count on you. Lol

[Smac770]

So decided to dig into why there's the different axles, and yeah. B8 introduced the new wheel hub (66.5 center bore, 42 spline, etc) and wheel hub bearing that the upcoming era would use across the board: B8 (8T 2007 A5, 8K 2008 A4, 8R 2009 Q5), D4 (4H 2010 A8), C7 (4G 2011 A6, 4G 2011 A7) [these are not US model year numbers]. As these products also used the same transmissions, the axles are all the same on the transmission side of the inner joint and the hub side of the outer joint. There's actually a specific set of inner joints and outer joints used across the board. The differences in the axles between families would then be the axle shaft itself, no doubt to accommodate the front track differences between the products.

The only time I ever found a suspension code specific axle was that rev R for the 1BR (rough roads, +13mm) in conjunction with FWD. The physical difference vs. the rev Q was a different CV joint, and some extra grease in both joints. Probably to handle the anticipated durability issues with the pavement for which people bought 1BR (though not offered in the US). This variance went away with B8.5, with both Q and R replaced by AH/AJ.

Regarding axle length, the 8K ones used on the 8K and 8T are 499mm "resting" and 465/467mm "compressed". The rev P is spec'd at 467mm compressed, and that's exactly what I measured on mine. It measured 500mm at rest. I don't know if the 8R/4G/4H ones that seem to be used around the Q5, A6, A7, and A8 are physically longer or actually the same, but I would suspect longer. Quick glance at a table seems to put them around 1-1.5" longer.


8K axles used on 8K and 8T; bold are current products:

capacity	application	initial B8.0 to Aug 7 '07	main B8.0	initial B8.5	main B8.5
low torque	4-cyl & 3.2L V6 quattro	8K0 407 271 C	8K0 407 271 P	8K0 407 271 AF	8K0 407 271 AL
mid torque	rest FWD, rest quattro	8K0 407 271 D	8K0 407 271 Q	8K0 407 271 AH	8K0 407 271 AJ
mid torque HD	FWD + 1BR	8K0 407 271 F	8K0 407 271 R	8K0 407 271 AH	8K0 407 271 AJ
high torque	2.7L V6 TDI FWD	8K0 407 271 E	8K0 407 271 S	8K0 407 271 AG	8K0 407 271 AK

Why did the mid and high torque B8.0 versions get replaced by the B8.5 versions, while the low torque did not? No idea. Overstock?



Starting with the outer joint, they are CV joints by GKN. It appears the 8R0 ones are maybe "SX" types? There's part numbers, but little specifics about the GKN product family or features beyond some physical measurements.

CVs used across B8, C7, D4; bold are current products:

part number	capacity	diameter / length	shaft splines	grease	A4/A5 axle usage
8K0 498 099	mid torque	100mm / 88.7mm	27	140g, G 052 738 A2	D, replaced by 099D
8K0 498 099 A	high(+) torque	106mm / 95.5mm	29	280g, G 052 738 A2	E > S, and used on 4H0 407 271 A
8K0 498 099 B	low torque	88mm / 79.5mm	33	90g, G 052 738 A2	C > P
8K0 498 099 C	mid torque HD	100mm / 88.7mm	27	160g, G 052 738 A2	F > R
8K0 498 099 D	mid torque	100mm / 88.7mm	27	140g, G 052 738 A2	D > Q, now replaced by 099G
8K0 498 099 E	high torque	99mm / 94mm	29	214g, G 052 528 A2	AG > AK
8K0 498 099 F	mid torque	94mm / 88mm	28	194g, G 052 528 A2	AH > AJ
8K0 498 099 G	mid torque	? / ?	27	?, G 052 738 A2	replaced 099D last month
8K0 498 099 H	high torque	99mm? / ?	29?	214g, G 052 528 A2	n/a, replaces 099E in some A8 applications?
8T0 498 099	low torque	85mm? / ?	25?	130g, G 052 528 A2 ?	AF, replaced by 8R0...099
8R0 498 099	low torque	85mm / 81.4mm	25	130g, G 052 528 A2	AL
8R0 498 099 A	high+ torque	102.5mm / 98mm	30	??g, G 052 528 A2 ?	n/a, used on 8R0 407 271 J

I didn't realize the CV joint grease was changed when they went from the B8.0 CVs to the B8.5 CVs.



The inner joints are AAR "tripodal" plugging triple-roller joints by GKN. There are two grades generally, the AAR 2600i and the AAR 3300i. I believe these numbers refer to the Nm rating. You can differentiate the with an axle in hand by measuring the joint, such as A measurement of 74mm is the 2600i; a measurement of 77mm is the 3300i.

There's an extra grade for two specific applications for the A8 4.2L TDI and the Q5 2.0 TDI with 0CK (FWD DSG). I don't know what this is called from the GKN side, so I'm just going to call it AAR 3300i+. Since I don't have a B8 Q5 or D4 A8 suspension workshop manual on hand, I do not know what the exterior measurement would be. It's likely 78, as the large boot clamp is only 0.7mm larger than the 3300i. Each instance of this + joint is only used in one axle part number and only for one particular engine/trans config.

Keep in mind that the parts catalog, from the Audi end, only lists field replacement parts. As such, it does not list the actual original build part numbers for the joints. It only lists "repair kits", which you can identify by the 98 in the part number: xxx y98 zzz. xxx is the parts bin, y is the main group (4=front suspension/drivetrain/steering; 5=rear suspension/drivetrain), 98 means repair kit, zzz is just whatever number. So instead of listing the actual part numbers like 8K0 407 341 for the AAR shell and 8K0 407 363 for the AAR triple roller, the catalog only states 8K0 498 103, a kit including all the parts including the boot and clamps. So if the boot material changed but the physical joint didn't, the repair kit revision (as well as the axle new part revision) is still going to change, masking what actually changed. Probably exactly how VW wants it, but not how Porsche does it.

rating	application	part number	measurement	adapter cap	shaft splines	A4/A5 axle usage
2600i	low torque	8K0 498 103 A > B	74mm	8K0 407 413	24	C > P
2600i ?	low torque	8T0 498 103	74mm	8K0 407 413	24	AF,AL
3300i	mid & high torque	8K0 498 103 > 8K0 498 103 D > 4H0 498 103 A	77mm	8K0 407 413 A	34	D,E > Q,S > AH,AJ,AG,AK
3300i ?	mid+ & high torque	8R0 498 103	77mm	8K0 407 413 A	34	n/a
3300i +	high+ torque - A8 4.2L TDI	4H0 498 103	??mm	none it seems	27?	n/a, used on 4H0 407 271 A
3300i +	high+ torque - Q5 2.0 TDI DSG FWD (0CK)	8R0 498 103 A	??mm	none it seems	27?	n/a, used on 8R0 407 271 J

Few comments on the above entries:

On all of the above except one, the triple roller is held in place on the shaft between a circlip on the shaft and a snap ring on the shaft end. The 8R0 498 103 does not use the circlip. Not sure if the roller is different or the shaft is different. As it only seems to be used in high torque scenarios on the A8 and Q5, I wonder if it's rated higher than 3300i.

The adapter cap fits over the end of the sleeve after the triple roller is inserted to provide a round surface for the large boot clamp to clamp around. The "plus" joint appears to not need this; maybe it's large enough that forging a round clamping surface on the end was inherent.

It's curious that they bothered to add the 0CK trans to the Q5 nearly at the end of its product cycle. And then needed a new triple roller joint (well, resurrect one they had used before) to handle the extra torque due to the 0CK's 10% stronger gearing vs. the 0B1 6MT, that just uses the 8R0 498 103.


Anyway, going to leave it like this for now. Tired of sifting all these incomplete details.

[Spawne32]

Well I bought GKN 8K0407271P axles, should I remain confident that they will work fine in my barely lowered B8? I did not realize there was this many damn variations to the axle. Interesting to see that there are in fact high torque versions, although I don't think anyone has ever really broken an axle before on these cars? The rear axles when I do replace them may wind up just being trakmotive/surtrack because of the prices.

[Smac770]

Low torque P is exactly what your car was built with (AL if Nov '11+). If you were K04 and were trashing axles, maybe move to a mid torque Q (now AJ), such as what the 3.0T quattro used. If you were doing a 3.0T swap and going stage 2+, maybe you'd look to move to a high torque E (now AK). Factory, the high torque ones were usually for FWD, where 100% of the torque (rather than 40% typical, 60% or 65% max, for quattro) is going to the front axles.

Then there's the A8 4.2L TDI. Even in quattro, the torque from that V8 diesel was big. D4.0 CDSB was 590 ft lbs, and D4.5 CTEC was 627 ft lbs. So full rear slip off the line, nearly 4600 ft lbs (6200 Nm) going to the front axles (627 ft-lbs * 65% * 4.714 1st gear * 2.381 final drive). Corner case, but has to be accommodated.

The Q5 2.0 TDI FWD with DSG gets up there because of FWD and gearing. The 0CK total ratio in 1st is 16.90, vs. 11.22 for the ZF8 used with the V8, and vs. 15.46 for the 6MT 0B1. 236 ft-lbs * 100% * 16.9 overall 1st = 4000 ft lbs (5400 Nm) to the front axles, all the time (well, ie, not just during full rear slip).

And yeah, there's no variance in the axles based on suspension code due to ride height. Be it -20mm for 1BD (S) or +20mm for 1BP (allroad). As long as you're using the 8K0... axles.

[Smac770]

I made a better diagram from the Porsche parts document that gives a better break out of the axle components.

Audi B8 C7 D4 front axle.jpg

11 and 18 are the c-clips, 17 is the snap ring that requires the pin pliers. 18 is the one apparently not used for the 8R0 498 103 inner joint. 19 is the cap apparently not used for the "plus" inner joints.

The xxx 498 099 outer joint kit includes 10-14, and grease, and the axle bolt 6.
The xxx 498 203 outer joint boot kit includes 11-14, and grease.
The xxx 498 103 inner joint kit includes 15-22, and grease.
The xxx 498 201 inner joint boot kit includes 17-18, 20-22, and grease.

Not sure why it won't show the image full size, it's only 730x470. You'll have to click on it to read anything.

[Kolbenringe]

This could have been quite helpful for me when I had to replace a CV boot in my A4- the parts lookups kept giving a larger CV joint (I think with 8 balls), but there was certainly a crossover that my car DIDN'T coincide with where it used a smaller, six-ball outer CV joint. Super weird and I originally ordered by VIN and got the larger one. A parts shop then took a chance and got me the right one from GKN. I even gave the part number for the axle and still got the wrong boot.

The Audi dealer told me that they typically have all the boots in stock and put on whatever fits when a customer comes in. They said they're all over the place and I also suspect that many get replacement axles that are of a different variety from the originals. If I was in the position to change boots on both sides, I likely would have opted for the more readily available 8 ball outer joint axles which I assume are from the S4. I also have the factory sport suspension. The six-ball axle I have is practically not available and it is the "P" variant on a 2.0 TFSI Quattro. The joint I have is an 88mm. So something weird is going on with my car. THe shaft stickers are P variants, but the outer joints are six-ball, 88mm versions.

Edit: link to more on my experience with the axles: https://www.audizine.com/forum/showt...1#post14553435

[fastboatster]

great info here. how do we know that a4q and fwd a4/s4 front axles are the same length? If this is from some ROW sources, it may not apply to the US/CAN since ROW quattro A4s came with DL501 like a US S4 (lucky ROW A4 owners didn't just get a "great" engine, they got a "great" transmission as well). Did I miss that USDM A4q and ROW A4q have the same front axle p/ns?

[Kolbenringe]

great info here. how do we know that a4q and fwd a4/s4 front axles are the same length? If this is from some ROW sources, it may not apply to the US/CAN since ROW quattro A4s came with DL501 like a US S4 (lucky ROW A4 owners didn't just get a "great" engine, they got a "great" transmission as well). Did I miss that USDM A4q and ROW A4q have the same front axle p/ns?

I have a German A4q 2.0 tfsi S-tronic. Both my axles have P stickers on the shafts, both are the 88mm outer joint with six balls. I can't state what is going on here. According to the chart, the P is supposed to be supercession of C, but this is a low-torque variant. Meanwhile, the B has the 88mm outer joint diameter. My replacement boot was also supplied with TWO grease packs.

[Smac770]

"The shaft stickers are P variants, but the outer joints are six-ball, 88mm versions." Right, just like the chart says. But maybe I was starring at this stuff too long and it's not so obvious from how I eventually posted the info. The 8K...099B CV joint, from the middle table, is 88mm, has 33 splines for the shaft, uses 90g of older grease, and was/is used in the C and P rev axles. So your axle is what it should be I would think. The B8.5 vehicles use the AL axle for that same "low torque" application, which has the 8R...099 CV joint (84mm, 25 shaft splines, and uses 130g of the newer grease).

I saw references to SX8 in the GKN materials, and I know the two 8R CV joints are referred to as "having SX tech" in one product intro doc. So it could be the 8R joints are SX8 8-ball joints. The technical information from GKN and Audi is very lacking, GKN in particular. But the reason I included the shaft spline count is because it means you can't take the 8K0 498 099B off a 8K0 407 271P and throw a 8R0 498 099 on it; the inner spline count is not the same, what I can find. And I also already explained that the part numbers for the joints here are Audi repair kits; the joints alone are physically stamped with a different part number. If you want a CV joint all alone, you'll have to figure out which xxx 407 305 revision it is for the one you want. The Porsche Macan small engine used 8K0 407 305 M, but who knows which 8K0 498 099 might use 305 M.

There's no difference in the front axle catalog pages for EU vs US. I have no reason to not expect the Audi 0B1/0B2/0B3/0B4/0B5 and ZF 0B6/0BK are all the same measurement between the flanges. It would have been a major failure on product planning on Audi's part for it not to be. The B8.0 S5 with V8 and 0B6 uses the same axles as the B8.0 S4 with V6 and 0B5, etc.

[Kolbenringe]

"The shaft stickers are P variants, but the outer joints are six-ball, 88mm versions." Right, just like the chart says. But maybe I was starring at this stuff too long and it's not so obvious from how I eventually posted the info. The 8K...099B CV joint, from the middle table, is 88mm, has 33 splines for the shaft, uses 90g of older grease, and was/is used in the C and P rev axles. So your axle is what it should be I would think. The B8.5 vehicles use the AL axle for that same "low torque" application, which has the 8R...099 CV joint (84mm, 25 shaft splines, and uses 130g of the newer grease).

I saw references to SX8 in the GKN materials, and I know the two 8R CV joints are referred to as "having SX tech" in one product intro doc. So it could be the 8R joints are SX8 8-ball joints. The technical information from GKN and Audi is very lacking, GKN in particular. But the reason I included the shaft spline count is because it means you can't take the 8K0 498 099B off a 8K0 407 271P and throw a 8R0 498 099 on it; the inner spline count is not the same, what I can find. And I also already explained that the part numbers for the joints here are Audi repair kits; the joints alone are physically stamped with a different part number. If you want a CV joint all alone, you'll have to figure out which xxx 407 305 revision it is for the one you want. The Porsche Macan small engine used 8K0 407 305 M, but who knows which 8K0 498 099 might use 305 M.

There's no difference in the front axle catalog pages for EU vs US. I have no reason to not expect the Audi 0B1/0B2/0B3/0B4/0B5 and ZF 0B6/0BK are all the same measurement between the flanges. It would have been a major failure on product planning on Audi's part for it not to be. The B8.0 S5 with V8 and 0B6 uses the same axles as the B8.0 S4 with V6 and 0B5, etc.

So if I need a new axle or just find it more feasible economically and timewise, I could just order high torque or S4 ones (which I believe to be 99mm/8-ball outer joints and they will fit in the hub and bolt right up to the transmission outdrive, right? I really don't know why, but the P axles are not easily available and often just go right to the ones with the larger joints.

[Spawne32]

So if I need a new axle or just find it more feasible economically and timewise, I could just order high torque or S4 ones (which I believe to be 99mm/8-ball outer joints and they will fit in the hub and bolt right up to the transmission outdrive, right? I really don't know why, but the P axles are not easily available and often just go right to the ones with the larger joints.

I had no problems getting the P axles from Europa Parts. GKN brand axles, however not use if they are reman's or new units. https://www.europaparts.com/axle-ass...k0407271p.html

[Kolbenringe]

I had no problems getting the P axles from Europa Parts. GKN brand axles, however not use if they are reman's or new units. https://www.europaparts.com/axle-ass...k0407271p.html

I'm not in the US.

[Smac770]

All the axles on any 8K or 8T has to fit into the same wheel hub and mate to the same trans flange shaft, and bridge the same gap regardless of suspension code. But I don't know if I would replace only one with a dissimilar variant. That said, sometimes they get odd. Such as the C7.5 A6 (4G) with 2.0 TDI and FWD used the 4H0 498 103 A inner point on the right and 8R0 498 103 inner joint on the left. WTF. But that's not the case with any 8K or 8T config. So want to use Q instead of P, go for it. Want to use a Q and a P, wouldn't be what I'd do.

If I look up 8K0 407 305 M (the initial Macan smaller one) on GKN's catalog (https://web.tecalliance.net/gkn/qa/home), it comes back as 25 shaft splines, 85mm diameter. So that would be the one used in 8T0 498 099 and 8R0 498 099. Which makes sense, as the AF/AL was B8.5, and that's when the Macan came out.

Actually, we get several actual hits in the catalog:

24683 - 8K0 407 305 D - 100mm, 27 splines - in 099 D, used in 271 Q
24683 - 8K0 407 305 H - 100mm, 27 splines - I assume this is in 099 G (which just replaced 099 D)? Seems odd since the 27 spline shaft usage ended Nov '11.
24685 - 8K0 407 305 C - 88mm, 33 splines - in 099 B, used in 271 P
24687 - 8K0 407 305 F - 100mm, 27 splines - in 099 C, used in 271 R
24691 - 8K0 407 305 E - 106mm, 29 spines - in 099 A, used in 271 S


36097 - 8K0 407 305 J - 85mm, 25 splines - so maybe the version used in 8T0 498 099?
36097 - 8K0 407 305 M - 85mm, 25 splines - so maybe the version used in 8R0 498 099?

The CV joints do differ in length as well as diameter, but as none of the differing diameters share the same spline count, each axle class likely has a different length shaft. Or the variation is not significant. The AAR joint has 50mm of travel.

[Kolbenringe]

Yeah, I'd only do a pair if I had more boot failures. The P-variant is basically only sold by GKN and Spidan-GKN. Prices aren't great in some cases, unknown remanufacturing quality (yes, GKN has some stinkers in the reman area). There are cheaper brands that likely use all Chinese reproductions. The axles with the 8 ball outer joints are plentiful on the used, new, and reman market. This all wouldn't be so tough if the part numbers were readable on the joint itself, but the rust is so thick, there is not a chance. I also find it interesting that the P shaft has 33 splines. I am really of the belief that in the replacement parts area, there's a funneling of the replacement parts customers towards the bigger joint axles.