2002 S8 Gearbox Question !!!!!

[HPsauce]

Hmmm. Leaks through those joints/seals, in my 14-year experience of D2 S8's, are a "feature". The wonderful aroma of the fluid dripping onto the hot catalyst lives with me even now.

But I've never lost enough to make a difference to the gearbox itself. And I've had a fair few seals replaced over the years.
Checking the level is a precise process that has to be done at the correct temperature.

[The_Laird]

I'm still at a loss as to why you don't get the gearbox flush and oil & filter change at Mackies - as more than one of us has advised. And ask them to inspect the rear output seal at the same time and advise on cost to replace if leaking.

It's much cheaper than a rebuilt gearbox and might solve the problems at a stroke.

[ainarssems]

Originally Posted by Ricky22buk

I'm considering trying something first before jumping into removing the box. My gearbox is perfect when cold but slips when warm and I think it might just be down to the oil level. There has been an oil leak from the drivers side of the gearbox where the drive shaft attaches, and I see from browsing online that you can relatively easily change the oil seal on that side, so I think for the value of an oil seal, some oil and a filter I will try that first.

Don't suppose anyone knows if thats a normal oil seal which would be readily available from a motor factor or bearing / seal specialist, or would it be a specialised seal only available from Audi ?

Oil expands when it gets warmer so it's more common to get poor performance while cold and oil level below normal, then it heats up, oil expands, level raises and problem goes away. The problem you describe does not sound that oil level is low. It sounds more like that you are loosing oil pressure when oil gets warmer and thinner.

There are 3 sealed compartments in gearbox, 1-gearbox itself, 2-centre diff and final drive and 3- front diff. Gearbox has ZF Lifeguard fluid in it, both diffs have gear oil in them. The leak you describe where driveshaft connects is from front diff and does not have anything to do with gearbox slipping.

As far as the seal goes you can probably get generic seal that will fit if you have measurements of old seal.

It really needs looking at/diagnostics by ZF specialist. If you keep driving with slipping clutches you will burn them out and then it will definitely need full refurb.

[IT]

^^^^ everything he said.

The final drive seal warps under the heat of the cats and lets out some final drive fluid. Only final drive fluid. This falls onto the cats and burns. Smells, but is harmless enough in terms of gearbox functionality.

The gearboxes don't / shouldn't leak.

For it to slip when warm (as apposed to cold) is odd - It sounds like a professional opinion on it before it gets much worse may save you an expensive fix later down the line.

[MikkiJayne]

The output shaft seals are custom sizes so you can't buy them off the shelf. The driver's side is only £15-20 from Audi though IIRC. Part number 01V409399.

That's not the cause of the slipping though. Barring low oil level, its likely the bearing between the first and second clutch packs has failed (a £6 part which can kill a whole gearbox!), then the o-ring which provides pressure to the clutch hydraulics also fails and you lose clamping force on the friction material which starts to slip. If you catch it soon enough you can replace the bearing and o-ring for about £100 diy, but if you've been driving with it slipping (and the oil smells burnt as per the Mackies response) then it's pretty much toast and will need a full rebuild. Flushing won't help at that stage.

Check the fluid level in the gearbox sump according to the proper procedure, and get a sample of the fluid. If it is clear and doesn't smell then you still have a relatively cheap option. If its a dark colour and smells burnt then its time for a rebuild.

Non-FE S8s have been going for for ~£1000 on ebay so if the car is in good condition apart from the gearbox it is still worth spending the money on a rebuild.

[Ricky22buk]

I would just like to say how I appreciate the very detailed and informative replies guys.

I thought that it would be worth topping up the gearbox to ensure the oil level is where it should be, and before I did that I assumed the right thing to do would be replace that seal I noticed leaking. It certainly sounds from the replies that the box is manufactured in such a way that the leak is nothing to do with my particular problem, and it seems more likely that I'm losing oil pressure rather than just being low in oil from the hot and cold oil description.

I simply thought it would be a good idea to try the oil and seal as a cheap effort to see if it helped before fitting the gearbox I already have, and as I live in northern Ireland, the cost of travelling to Mackies to get a filter and gearbox flush wouldn't be viable as I know in my own heart of hearts that there is a high percentage chance I'm going to have to fit the new gearbox anyway, so the costs all add up.

I have a reconditioned box here for the car, which was supplied by the forums sponsers, along with a new torque convertor reconditioned by Mackies, new filter and oil. So basically everything to do the job, but just thought it might have be worth the effort to try this first. Seems like the general consensus is that I should just fit my new gearbox as the perception is an internal problem rather than an oil level. I do understand there is a procedure for filling and running the gearbox to fill it properly at a specific temp.

The last few replies have convinced me that I shouldn't waste my time on my so called cheap fix !!!!!

Thank you one all all !!!!

[Ricky22buk]

Right bit the bullet...... old box out and replacement now fitted. I have a few odds and ends to clear up before I look into these next two steps.



1. When I removed the engine cover below, I realized I have a very bad oil leak on the left hand side of the engine, and although its hard to tell its origin without washing and driving again, online reading seems to suggest the transmission fluid is pumped through the radiator as a means of cooling it and that seems to be a problem area for leakage.

If it is in my case can I ask where would be the best place to buy a new radiator, basically somewhere that would have it sitting on the shelf so I could get one dispatched asap ? I'm assuming this could well have been my problem all along with the leakage of transmission fluid.

If this isn't where my leak is coming from, should I even attempt to remove the old oil from that pipework and cooler loop considering I don't have access to the specialist machine you guys keep taking about ? I hate the though of mixing it with the new oil I'm putting in the box !



2. Also, I'm a little confused with the oil filling procedure. When your car is on the ground and via the gear lever you select first, you cannot select second until you are doing above a certain speed, which I assume comes from a wheel speed sensor.

So if the car is on a lift and the procedure tells you to go through selected gears for 30 seconds each with your foot on the brake, I'm assuming you shouldn't be able to select all the gears without the wheels turning ?

If this is a stupid question please tell me and I will apologize !

Thanks in advance guys !

[MikkiJayne]

I use Exeter Radiators since they're near me. They have a bunch of different suppliers and usually can ship direct from source so quite quick. Worth a call http://www.carradiator.co.uk/

Not sure how much one is for an S8 yet as I haven't asked them. Euro Car Parts are £500+ and not in stock. My copy of Etka says £430 for a genuine one, which may be a bit out of date.

You'll not get all the old oil out of the box unless you strip it down. The TC will still be full too. Best you can do with a drain and re-fill is about half of it I think, without the special machine. Its easy enough to drain the lines to the rad, but not really worth it unless you're swapping the radiator anyway.

Not sure about the gear procedure - I always assumed the wheels were spinning to do it.

[Adrian E]

Current price for a rad (OEM) is about £500 before discount

With gear selector, you do not need the wheels to rotate. By moving the selector through the available modes (which if your car pre-dates S mode includes 2-3-4) you're allowing oil to flow through parts of the box statically before it's driven.

It would be crazy to attempt to have the wheels driven at road speed on a lift

The main challenge when filling the box is keeping the oil temperature low enough - main thing is to get as much in there as possible before starting and have an assistant to monitor oil temp with VCDS and move the gear selector as required while you're under the car pumping more fluid in there.

Worth making sure you can actually get the oil in without just spilling it over yourself!

[Cornershop]

Genuine rad a bit cheaper here:

http://www.genuineautoparts.com/uk/a...omponents-scat


Not used this company myself but others have, appears legit.