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  #11  
Old 28th January 2017, 12:43 PM
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27litres 27litres is offline
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It wouldn't surprise me.
Once the ECU recognises the MAF is gone and gives the fault lights, the TCU seems to go into a default shift mode - if anything the gearbox shifts softer I reckon, and I drove it gently anyway knowing it wasn't working at its optimum.

I have my own ideas on why these gearboxes fail, but I won't start that debate here!
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  #12  
Old 28th January 2017, 01:14 PM
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Quote:
Originally Posted by 27litres View Post
It wouldn't surprise me.
Once the ECU recognises the MAF is gone and gives the fault lights, the TCU seems to go into a default shift mode - if anything the gearbox shifts softer I reckon, and I drove it gently anyway knowing it wasn't working at its optimum.

I have my own ideas on why these gearboxes fail, but I won't start that debate here!
Why not?! everyone else does! ...and its a subject of huge concern to all D2 5HP19A owners as its often a do or die issue. Its been covered comprehensively in the transmission thread but any other contributions would be read avidly. Seems un-Australian to hold back
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  #13  
Old 28th January 2017, 02:18 PM
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Alright David, as you insist ;-)

I doubt this is an original idea and it's based largely on what I read (and saw) on what I'm sure was this forum, where an AME (Aircraft Maintenance Engineer) partially rebuilt his own gearbox. And on talking to a gearbox expert during my recent 'scare':

Most failures seem to be caused by a failure in the Clutch A Basket. Probably due in large effect to Clutch A being engaged for reverse and first gear (and I think second gear), it will be under one of the highest torque loadings of any of the baskets.
I think the bearing surface on the front face of the clutch A basket is a little weak or thin (the bearing surface is like a little shim mounted in a recess on the clutch A basket surface).
Over many revolutions, this bearing surface wears down to the point that the clutch A basket can move slightly back and forth on its shaft or alignment path. This in turn puts stress on an o-ring seal on the inside of the basket causing it to fail.
This then results in the loss of reverse and/or first gears (and potentially second gear too I think, but it's irrelevant because by then you're in limp mode).
This normally damages the clutch A basket too which requires replacement, but by the time you've gone that far in a shop, you're doing a rebuild anyway.

So I'm not sure there's anything that can be done to prevent this eventual failure. There may or may not be improvements to the bearing surface in the 'improved design' baskets.
I employ a strategy to attempt to maximise the gearbox's chances, and that is to change the fluid regularly to refresh the fluids consumables, such as plasticisers (to regenerate and preserve the o-rings and other rubber components), friction modifiers (improve shear strength of molecules to improve lubrication particularly under pressure), and detergents (to keep components in the transmission clean and free of contaminants). Fresh fluid on its own also provides the best possible lubrication.

In this way, I attempt to minimise wear on the bearing surface of the clutch A basket as much as possible while also doing my best to protect the o-ring. Failure may still be inevitable, but at least I'll know I gave it it's best shot.
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2002 Audi S8 - Project
Replacement head coming arrived thanks to MJ
Silver with Black interior. All features as the '01, with the 'S' mode auto shifter. Dodgey rear tint (need to find a way to get rid of that).
Family:
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- has a louder more obnoxious exhaust than the S8, sounds great! Love this thing - Q7 was double the price, and certainly not double the car!

Sold:
1997 Audi A4
- Hamilton's Club Sport, Achat Grey (will miss the old girl)
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  #14  
Old 28th January 2017, 08:02 PM
MikkiJayne MikkiJayne is offline
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Good summary

I replaced the problem bearing, carrier, and o-ring in mine as a preventative measure while the engine was out. It was actually in pretty good condition, as was everything else in there so I hope it'll manage another 100K with regular oil changes. I'm going to do the same with the FE while that's in bits too.
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  #15  
Old 28th January 2017, 08:24 PM
HPsauce HPsauce is offline
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I guess if you "know" (or have high confidence that's a likely cause of failure) you factor it in to the running costs, change the fluid regularly and get the box fixed at the first hint of failure.
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  #16  
Old 29th January 2017, 11:48 AM
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It does all go to show that regular servicing /fluid change is the way to go to prolong life.
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  #17  
Old 18th December 2022, 06:22 PM
Sit down, Waldo Sit down, Waldo is offline
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Bit of an old thread resurrection here, but I've been experiencing the same problems for a little while. My OBD started to suggest the MAF sensor & VCDS seems to have backed this up.

So, where's the best place to get a new sensor from?
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