MikkiJayne

Hi all,

I've only just got my 02 S8 back on the road after replacing the motor, and now I'm getting a bad shudder from the transmission Its worst in 3rd at low rpm (<2500) and light throttle - the car feels like its driving over cobbles. But, it does it in 1st and 2nd occasionally too, in D, S and Tip. 4th and 5th are fine at high speed but at low speed the rpm hunts up and down like the TC is locking and unlocking. Its much less noticable when everything is cold, and gets worse and worse as it warms up.

While the drivetrain was out I dismantled the transmission and replaced the problem o-ring and bearing on the first clutch pack and also the oil pump after a mishap reattaching the motor and trans

I only drove it 300 miles before I took the motor out and I don't think it was behaving this badly, otherwise I wouldn't have bought it so I suspect I did something wrong when I put it back together but can't work out what. It had new OE fluid and filter when it went back together and was filled according to spec at 35-40*C. The clutch drum was fine btw - no damage and I inspected it closely for cracks.

So, does anyone have any ideas please? The new motor is glorious but the sick trans really spoils the experience

A pic of the family cos we all like those:

jfrahm

Did you check the torque converter lock/unlock valves when you were in the trans? They come out when you replace the problematic main pressure control valve in the lower valve body.

If those are OK I'd wonder if your fluid has the right friction modifiers for proper TC clutch lockup.

MikkiJayne

I didn't touch them, or the control valve. I will look them up though thanks. I removed the valve body to let all the old (red) fluid drain and then put it back. I only did the o-ring and bearing as 'preventative maintenance' which in hindsight seems to have been a mistake. It wasn't broken, so I fixed it until it was

Its genuine fluid - G052 162 A2. It took 9.5 litres of the stuff, with probably half a litre of that in the drip tray so I think the level is right.

Its definitely temperature related. Driving 2 miles to the workshop this afternoon it was just fine, but as it warms up it gets worse and worse to the point that its almost undriveable.

jfrahm

I have heard that TC clutch issues feel like driving over "rumble strips" which are cuts in the tarmac to buzz or rumble when you drive over them. I wonder if one of the pistons is hung up, if not maybe the TC clutch is totally shot. You could always try some shudder fix, which I think is just more friction modifier, as a last resort.

MikkiJayne

That's exactly what it feels like.

Could driving it when the trans was low on oil permanently damage the TC? The PO had stuck the trans sump on with bathroom sealant so it was leaking oil everywhere. I only realised when it started whining on acceleration and behaving badly - it did about 20 miles like this before I pulled it apart. The oil level was up to the joint between the pan and casing so about 3 litres short.

I wonder if that did the damage and fresh fluid has made no difference?

MikkiJayne

For future reference, it was indeed a bad torque converter.

Thanks jfrahm for the suggestion

the_duke

Thank you for checking back and letting everyone know what the solution was. Too many threads with no final answers.

spitanddirt

Just to throw something else into the mix.....I have the same problem on my 2000 A8 but I have 225,000 miles and I just installed my 2nd timing belt, water pump, etc. this year in February. Well, here is my $0.02: I replaced all my ignition coil packs using what I thought was a quality product October of 2013 --- Standard Motor Product UF274 from RockAuto.com. Well, the picture they have is misleading, just like all the other online retailers using the same stock photo. What I received was a product that was made in China and has lasted, not reliably, since then. I kept all my good original coil packs as emergency back up units and I'm glad I did.

The reason I even bring up this topic when the original poster had a problem with the transmission is that my car felt the same way until I started having my "replacement" coil packs fail. I've installed two of my original coil packs and my car has stopped shuddering. I'm not saying that my torque converter/transmission isn't worn, but what I am saying is that I think that my cheap China coils may have been allowing stray voltage into the vehicle's electrical system and possibly causing sensor/solenoid issues with my torque converter/shift solenoids.

I know it's a long shot, but I am currently ordering a full set of OEM (Made by Hitachi) coil packs.

silverd2

Original trans? Ever a rebuild? What mileage on the car when you bought it? Ever have or do an ATF/filter change? ...when (mileage) and how often?

Yes I'm writing a book ... in my head

Cheers

twentysevenlitres

Accumulating ammo Sam? ;-)

That previous transmission with all the fluid changes got a fair old life - 180,000 miles (that's 300,000km). I'd accept that as having done a good job!
These 100,000-120,000 mile failures are too short IMHO.

The original transmission in my car went at 140,000km (85,000 miles) - way too short a life. PO had it rebuilt and it's now at 210,000km (130,000 miles). So 70,000km (45,000 miles) on new Trans so far.

Without hijacking this one, I'll give you a full thread on this, as I've actually got a new issue with it that I think I know what it is, but would like to put it out to the community...