My not so daily 4.2 Quattro thread

[Rich81]

Finally got the gear box sump off yesterday to do the filter and oil. Not too bad a job even with the car on the floor, however you do ideally want to be indoors as the gearbox internals are exposed to the elements; a windy day outside would end up with bits of grit getting in there!

I genuinely half expected to find metal in the sump, having read so many posts of failed HP24 gearboxes. However first good sign when the sump was off was that the filter was dated 2013, so it's been serviced before. I do have full service history for the car which mentions gearbox oil, but that could have been the transfer box so I wasn't sure if it had ever been done.

Everything looked ok in there.

Second good point was the sump contents was good, no metallic pieces on the magnets. They do accumulate a kind of paste of super fine metal particles which I would expect is normal, and is wiped off before it all goes back.

Now the first area of question was did I have the correct filter. The reason I was unsure was because there is a small O-ring that goes on the small neck that pushes up to the gearbox, however when offering the new filter up it seemed too small. An O-ring should give a snug fit into the recess it goes into but this didn't, in fact it appeared to be a couple of mm smaller diameter to the recess it went into. The new filter was exactly the same as the old filter though, but didn't seem right somehow and I wonder if there is a different seal that is needed for this gear box variant...

I didn't notice at the time as it was covered in oil but the old filter was actually cracked, quite badly, so it's possible this could have been causing a problem with oil pickup!

Got the sump back on and proceed to fill up. It took 5 litres cold. Then went into the filling procedure and it took another litre or so before hitting level. I had done this before so it was quicker and easier but still ended up with oil everywhere.

So now I have pretty much all new fluid in there, having done the flush just a few weeks ago, with a new filter, however a question about if it's fitted woth the right seal, or even if it's the right filter...

The old O-ring was fitted as in the picture at point A, which is where I put it on the new filter. However I am now thinking that maybe it should be fitted at point B, which is a bigger diameter and would stretch the O-ring a bit, it may be where it's supposed to seal to the box... I couldn't find any literature on this. Can anyone who has done this confirm what type of seal and where it should go on the filter? The O-ring had a very small OD approx 2mm.

I have a feeling I may be doing this job again at some point in the near future.

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[Rich81]

Have now had chance to get the car out for a proper run and what a difference, the gearbox is noticeably smoother now, particularly on part throttle at low speed. Gear shifts are smoother and so far no slippage or dodgy shifts. Tiptronic mode is particularly more smooth and you can hardly notice the shifts at all. Seems like the cracked filter may well have been causing an issue!

I am very glad I did this job when I did! Not too worried about the o-ring as all pictures I've seen show it in point A on the pic, however still not convinced it's right... driving lovely though.

Despite being expensive to run ot is such a nice car drive. Even with the Quattro sometimes see traction control flickering on in 2nd at 60mph, V8 with a miltek exhaust sounds like a supercar... beast!

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[QuattroCalum]

Good to hear you've dodged a bullet, thinking about it the cracked filter would have caused a drop in oil pressure causing all sorts of anomalies.


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[quattrojames]

Great thread, makes me realise I should spend more time on here and how much I miss tinkering.

Removed the TV aerial - no use to me as they don't transmit non-digital anymore.

Don't know why I want to keep the RNS-D I just do. Always liked to keep period stuff in the car and the Bose system sounds great.

I like the D too, I fitted a 12v digibox to mine and it works well, although I do need to pull my finger out and get a better aerial... not that I ever actually sit in the car and watch TV!

 

[Samuel c5 Q]

If you put the seal on B you may have found that it would have fouled on an opening that it is supposed to mate with making the filter would not have seated properly. Good job that it's going well.

 

[Rich81]

Great thread, makes me realise I should spend more time on here and how much I miss tinkering.



I like the D too, I fitted a 12v digibox to mine and it works well, although I do need to pull my finger out and get a better aerial... not that I ever actually sit in the car and watch TV!

Digibox sounds cool, just because not many people have a TV tuner in their car. I am tempted to fit some kind of android box so that I can do YouTube etc through the RNS-D but at 640x480 resolution it isn't going to look very good.

I have got hold of a reversing camera from eBay which works well but I can't find a good place to permenantly fit it...

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[Rich81]

Crazy stressful week at work and glad it's Friday. One way I like to de-stress is put some music on in the garage and do some jobs on the car.

Tonight had an easy little job of replacing the rear ARB drop links. Had an annoying rattle for a while and on inspection was clearly from these. Interestingly Elsawin says remove the brake caliper and bottom shock mount, but there's no need! There's just enough room to get the bolts out. Just make sure to Jack up and axle stand both sides of the car evenly to take tension off the ARB. Then before tightening stick the Jack under the shock and compress to take the full weight of the car before doing up the bolts fully.

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[QuattroCalum]

Crazy stressful week at work and glad it's Friday. One way I like to de-stress is put some music on in the garage and do some jobs on the car.

Tonight had an easy little job of replacing the rear ARB drop links. Had an annoying rattle for a while and on inspection was clearly from these. Interestingly Elsawin says remove the brake caliper and bottom shock mount, but there's no need! There's just enough room to get the bolts out. Just make sure to Jack up and axle stand both sides of the car evenly to take tension off the ARB. Then before tightening stick the Jack under the shock and compress to take the full weight of the car before doing up the bolts fully.

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This is one of the advisories on my mot, good tip there . It looks very tight in that photo.


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[thawatchai2510]

CHEER.

 

[Rich81]

It's been a few months since I posted on here and I wanted to update on my gearbox situation. I'm pleased to say that it is now completely fine! However, the filter and oil change, where I found the old filter was cracked, was not the end of the story!

Because these HP24a gearboxes have some bad press I think it's important to post this update.

So about a month after the filter change, everything had been fine and then I started experiencing the shifting issue come back, occasional jolt between gears, rough shifts, generally only from cold and just didn't feel right. At this point I thought it was the end of the gearbox after all the threads I had read. I had looked into changing the pressure control valve and was going to drop the valve body and try changing this as a last ditch attempt. Then I stumbled on an internet post somewhere I think it was a jag or land rover forum, which uses the same gearbox, where a guy said always re-check your oil level a few hundred miles after a full change.

Now I am pretty meticulous when I work on my car and I was damn sure I followed the fill procedure correctly, checking temps on vag-com etc, and the box was definitely full.

However, I got her up on in the air and checked the level. Ran up to temp and no oil came out so I thought, ok I'll top it up a bit maybe it was low. I had to put in another 800ml before it was at level!

Then drove her and the shifts were perfect, take-off was better, everything smoother. And it has not missed a beat for the past 1000 miles.

So either two things happened here either I had a leak or the fill procedure did not work properly the first time. Perhaps there were air pockets somewhere in the trans, fluid not fully circulated etc. In the ZF HP24 manual for the gearbox, it describes the fill procedure and says put the box in manual and shift up and down through the gears, but don't allow the road wheel to turn. Now in the Audis you can't do that - you can't change out of first unless the car knows you are at speed. This may be possible to do in the land rovers or jags that let you pull off in any gear. Perhaps this is an important part of getting the fluid fully circulated that you can't do in the Audi, or perhaps you should let the road wheels spin and go through gears. I don't know.

But what I do know is that if you have one of these gear boxes and you experience any kind of shifting issues, you need to perform oil and filter maintenance ASAP, and re-check your oil level after a couple of hundred miles.

These gearboxes have bad press for catastrophic failures of the drums and seals. But another thing these cars suffer from is oil seal leaks from the gearboxes. The rear transfer box seal goes due to heat from the exhausts (had to do mine) which loses transfer box oil, but also the output shafts for the front wheels oil seals go (both mine have been done on the service history, and show some very minor signs of weeping now). So perhaps the root cause of the failures on these gearboxes is that they ran low on oil due to poor maintenance (Audi instructed lifetime oil fill, owners don't want to pay big bills to have what look like minor gearbox oils leaks, MOT advisories etc).

I have to say I love this car. I have not had to do anything else to it recently apart from a new pair of xenon bulbs. I have the MOT coming up in a couple of weeks which I think will be fine, with the only concern being possibly emissions (high miles, stinks of fuel sometimes on startup).

For the future I am considering upgrading it to S6 spec as there a few S6s around with blown boxes. I would like to get the front seats at least but would consider a donor car for the right money and change the clocks, some of the trim, and potentially some of the engine parts (I believe the extra horsepower is by virtue of different inlet but need to do more research as if it's different cams I wouldn't bother).

Oh and she's been a lot of fun to drive in the snow!

 

[RSTHRILLER]

I HAD BEEN LOOKIN FOR A6 4.2yrs for A decent one know a d2 s8 has come up with the 4.2 what do you think of the engines reliable?

 

[Rich81]

I HAD BEEN LOOKIN FOR A6 4.2yrs for A decent one know a d2 s8 has come up with the 4.2 what do you think of the engines reliable?

They are reliable. Mine is on 172k miles. As long as they are looked after there is nothing to worry about as the V8 is just being tickled on normal driving.

That being said any work you do need to have done is going to be expensive on a car like that so if your not doing the work yourself be prepared. For example I repaired my variable inlet manifold myself which cost me nothing but a garage to do it with parts would probably be nearly a grand. You are looking at a grand for the timing belt to be done etc. Transmission seals do fail which are expensive.

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[RSTHRILLER]

How hard is it to change box oil is it worth doing

 

[Rich81]

How hard is it to change box oil is it worth doing

In my view it is essential maintenance. A failed box will write off the car in terms of cost. It's more involved than an engine oil change. Car has to be in the air, level, and the sump has to come off. It's about £100-150 in parts. You need a laptop with vagcom to check oil temp.

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[Rich81]

I thought I would update this thread as there's many C5 4.2/S6/RS6 owners with the HP24A gearbox still going that may have had slipping issue and wondering if their box is knackered.

Well since I replaced the oil and filter in mine last year, it has been good ever since. That's about 5000 miles of mixed town/motorway driving. Not many miles yet but at least it kept the car on the road. However I have had to top up the gearbox oil a couple of times. There is a small leak which appears to be some internal seal somewhere, that results in about 500ml lost every 1500 miles. The box can start to be a bit less smooth changing when the fluid gets low. It's so quick to top up I don't mind and I probably could do it once a year and get away with that. I've heard RS6 owners check the oil level every year and top up as this is common and doesn't warrant a box out job to replace the seal.

I haven't really had to do much else to the car other than having the AC compressor replaced at the start of the summer, that was knackered when I bought the car. Quite an expensive job to get done at the local VAG specialist but worth it considering the heatwave we had this year.

Unfortunately I have just noticed the the final drive output seal has gone again. Having had this replaced 15 months ago at a cost of about £350, it's disappointing to see it's gone again so soon and I thought it would last a good few years which would probably be the lifetime of the car. however, the tell tale smell of burnt gear oil on the exhaust and small patch on the garage floor is there again.

I've had this car 18 months now and I still really like it. The C5 A6 is such a solid car and the V8 with the Miltek exhaust is probably the cheapest supercar type sound you can get and sounds incredible in a multi-storey car park I was toying with the idea of getting hold of a C5 S6 but the cost of maintaining these is pretty high. I still have some concerns the gearbox will fail one day out of the blue and now I have to replace the final drive seal again. This time I'll probably attempt it myself which is a pain on the flat ground without a lift, but I can't justify the £350 to have someone else do it at the moment.

These are great cars if you don't mind doing the work yourself but if you need to get everything done in a garage then there could be a £500 - £1000 bill around the corner at any moment. Having followed Ron's thread, I'm seriously impressed by the work that's gone into his S6.

Having recently acquired an A4 B7 TFSI Quattro as a daily, I now I have to decide whether to keep spending time and effort (and lots of money on super unleaded) on this or move onto something else. I may fix the output seal and see how I feel after that.

 

[Bratcop]

I would look very closely to determine if it is the final drive seal or possibly the two pictured seals that are meant too keep fluid from seeping out the breather hole in this gear set. If the two seals on the end of the black tool I had made (brown seals on black tool pictured) aren't seated squarely and set and at the correct position inside the pictured gear set, trans fluid comes out the visible hole in the gear set, then comes out another breather hole and does a great job mimicking a failed final drive seal.

I know because I had my final drive gear out about 6 times because of this leak. I finally had a machinist friend turn that tool out of phenolic to ensure the seals remained evenly spaced and square inside that gear set.

Just something to consider.

Bratcop

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[Rich81]

Been over a year since the last post on here but I thought it would be worth an update for future reference especially for anyone with one of these cars.

Early 2019 I replaced the final drive output seal myself. The previous one had lasted about 18 months. After I replaced this seal the transfer box was sdry and seemed fine. I still had some ATF fluid leak from somewhere but still only a very small amount. Because I don't do many miles I don't mind topping up the gearbox every 3 months. However because this is about 1k miles between top ups it's not something I want to keep doing forever. The problem with these cars really is the gearbox reliability all because it struggles to keep its fluids inside. The car isn't worth putting a new box on and I don't have the space to pull the engine and box and do a box rebuild either.

A month ago I noticed the tell tale sign of burnt gear oil on the exhaust again and what looked like the final drive output seal leaking again. This is after 1 year and only about 2k miles (mostly short journeys though). The old seal looked good and had a good fit on the shaft so as the above post by Bratcop notes, it may not be the output seal this time. I have replaced it anyway, but we will see. I won't be rebuilding the transmission or anything like that on this car as I don't think it's worth the cost however it may well give me another one or two years of use. Replacing the output seal is cheap and easy so I don't mind doing that job once a year if I have to.

Nothing else has really gone wrong with the car which is a testament to the C5 platform. I would love to do a manual conversion but it wouldn't make much sense to do this on a standard 4.2 and I would rather source an S6 with blown gearbox to do it on if I was going to go to the trouble.

All in all 3 years of ownership and great car. Very comfortable (always liked the C5 platform), engine never missed a beat, sounds brilliant with the Miltek exhaust. Gearbox always a concern and took some of the enjoyment away from the car.