Gearbox Teardown & Refurbish - 6HP28A61

[ATinOf]

The grand finale (Chapter 4) of the epic saga - This will be a truly epic post due to the sheer number of images, you will need a brew with you when you run through all of this. And you may want to check back when I have added the full commentary before you do so.

This one covers the actual tear down of the RS6 09E gearbox, including the valve body, complete refurbish (frictions, steels, seals and bushes) and rebuild. This is DIY at its very best, but not for the feint hearted.

The related chapters of this epic can be found here;
Chapter 1 - Engine / gearbox removal covered here: viewtopic.php?f=47&t=129282
Chapter 2 - Making a gearbox stand covered here: viewtopic.php?f=47&t=129271
Chapter 3 - Removing the Gearbox from the Engine: viewtopic.php?f=47&t=129515

And it goes without saying this is not necessarily the best way to do this task,its how i did it; follow this method at your own peril!

In my instance the Audi code for the gearbox is an 09EA, the model on the label being a KZQ
In terms of ZF this is called a 6HP28A61 (which is a second gen over the first gen 6HP26A61);the model code being 1068.090.003
The ZF parts catalogue for my box is code 1068.079.009
The Torque converter is a ZF-SACHS K110

If your box codes differ from these then its likely there will be differences not reflected here, and parts may differ to those I list (I also provide no guarantee I list the correct part numbers, we are all human, please check them yourself!)

[ATinOf]

WTF??? - I know, its a bench

But that's not why its here - I cannot stress enough how important a clean working area is when working on an auto box; I find good quality brown paper is excellent for lining the bench, when it gets dirty wack on another piece - too easy for words, but words you've got.

[ATinOf]

Make sure you collect all of the oil so that you can filter it and check the size of any solids found in it as part of your diagnosis, we'll come back to the results of that later. The colour of the oil also tells a story; in my case the gearbox fluid was a light brown, it hasnt done all that many miles as I've had it changed once; but the diff fluids were a dark brown - I collected it all in a single container but you are better off collecting it separately for filtering if you can. Extra large coffee filters are good for this, albeit slow going as they are a very fine filter.


Starting at the front diff the of side drive shaft stub needs removing. there is a circular spring clip holding this in place much too strong just to pull off (if it does pull off you need a new spring clip! Regardless its recommended to replace this spring clip anyway); I used 2 small strips of steel flat bar 1" wide behind the bolt holes against the housing and drove 2 of the bolts through the shaft securing holes to push it off against the housing evenly.


There is no drain plug on this cover, so I let the fluid fall out, the rest of it will spill out when we undo the housing screws. Undo in sequence 11 thro 1


Now this was a perilous photo moment; you MUST always hold this gear as it is highly likely it will fall out, it will probably come away with the housing in actual fact, but whatever you do don't let it fall on the floor!


If you have followed my prior posts you will know I suspected this green O-Ring of failure due to oil leakage, it was mis-shapen at the top side and there are 2 distinct marks on it at the top, I believe its been off once and trapped at some point in its life before me - it should have been replaced


I suspect Its typical of the rear bearing race of this gear to be left in the bell housing in its seat, but its not a tight fit so don't be too concerned if it comes away with the gear

[ATinOf]

If like me you are thinking 'where's the magnet', don't panic, its on the back face of this cover





Always inspect the fine metal particles on the magnets when you clean them, they should be 'fine' - no bits of metal greater than 1mm in size says the book.... you shouldn't see anything near that size in a healthy diff!

[ATinOf]

Now for the near side drive shaft stub; this one is secured to the bell housing with 3 screws on the plate behind the shaft fixings


With even levering this one will come out a little easier with its bearing intact; if you are not changing the seal at the front diff where this shaft meets the diff gear you need to support the shaft end as you draw this out very carefully; I was replacing this seal anyway so it pulled out easily





Now the torque converter can be drawn out of its seals against the input shaft, and no - you do not need the ZF tooling for this!! (I mean really, pull out handles? There's a convenient flat triangular plate to pull on!!!). As I have stated in prior posts this torque converter has clearly been out before and may not be original; these pen markings are not mine.

[ATinOf]

Lets get the gearbox mount off next, starting with the main bracket





And then the rubber mount itself (you could have left the main bracket on this but I wanted to inspect the rubber mount and clean all the crap off everything before it went back together)





Now access to the plate securing the mount to the gearbox is gained, which needs to come off if you are removing/splitting the rear output diff

[ATinOf]

Now to remove the transfer case oil cooler flow and return external pipe lines from the rear diff to the front bell housing (where they couple to the oil cooler)


As you can see I had some trouble with a screw here, malgrips are an essential tool! Clearly I need to add this screw to the shopping list (not a standard stocked part, special order from ZF if like me you want an original, part number 0736.101.510, M6 x 15 Torx screw if you Shop elsewhere)






Now the top (flow) line can be removed, and expect some spillage from it


Followed by the lower (return) line, again spillage is inevitable from the line




Now don't go losing this spacer that fits behind the retaining stud clamp. Its quite important, it ensures you dont crush the lines!

[ATinOf]

You dont need to remove this (torque converter, gearbox input speed) rotation sensor, but to ensure its not damaged its wise to

[ATinOf]

Onto the output diff - and remove the torsen diff housing on the rear at the output shaft end. Undo in sequence 7 thro 1




Remove this shim washer before it falls off


And remove the rear transfer case, undo in sequence 19 thro 1


And this mis-shapen shim washer



And withdraw the loose intermediate output shaft

[ATinOf]

Remove the steel gasket and discard


Look closely at the niche there sits the magnet



Again inspect the fines on the magnet whilst cleaning it


Remove this shim washer from the gearbox output shaft

[ATinOf]

Now is a good time to check the gearbox input shaft axial play and record it, you could have done this earlier, as long as its done before the gearbox is stripped.

You may well ask why we haven't done the diff output axial play, its unlikely this will be worn to the degree of concern on this low mileage car and I was not planning on fine tuning the diff clearances. We are not changing any diff components.

However since we ARE planning on changing frictions and steels where required in the gearbox we WILL be affecting the gearbox axial clearance. Besides which given the inspection so far hints at this box being off at least once before I want to know where it stands now, to determine how good a job was done! Push the shaft in to datum the DTI


Clearance is actually within spec, 0.2-0.4mm ; however since the spec states this clearance is 'dry', given this box is now 'wet' (i.e. its oiled up) I suspect the clearance was probably greater than this measurement when dry, by how much I couldnt guess. The measurement is also to be taken at 200N force (ie a 20kg pull, which isn't easy to do on the splined shaft! I attached a jubilee clip and some insulation tape to get a good grip; of course there is always the ZF tooling you can buy!)

[ATinOf]

Now to remove the oil coolers, starting with the transfer diff oil cooler. It seems we have some more screws to order; malgrips put to use again!
These screws are Audi supply; 01V 919 838, although they are the same M6 x 15 Torx fixings as the cooler pipe screw; ZF dont list them for the gear oil coolers.




After the transfer diff cooler remove the gearbox oil cooler adjacent

[ATinOf]

Now its time to remove the sump pan, undo bolts 13 thro 1 in sequence



Exposing the gearbox oil filter and the valve body


As I have already stated the fluid in this box has been changed once, and its nice to see there has been minimal build up of crap on the sump since (and reflects the job was done properly)


I you wanted to (if you suspected a shitty box) you could rip the filter apart and inspect the element; given the condition of the oil I removed there isnt any point in that for me

[ATinOf]

Now to get the valve body out, starting with these 4 base screws at the side of the solenoids


VERY carefully unclip the loom support from the screw heads (held at 2 I think), be warned this gets brittle and if you break this at the supports (they only clip on) you should replace it, it should not be left to dangle on its own, you run the risk of stressing the cables at the connection ends


Now remove the clip holding the connector sealed inplace



Unscrew the Torx40 larger headed M6 screws, ten of them I think, holding the valve body to the gearbox - ** NOTE there is a sequence to follow for these screws to ensure you do not introduce warping into the valve body ** which is essentially start from the out-side (10) and work your way inside diagonally (to 1)


And carefully lift the valve body out, along with the double sealed connector body (with a slight twisting motion and a little WD40, since we are replacing the seals anyway, to aid it out)

[ATinOf]

Considering its suspected the box has been worked on once, this looks like its the original gummed up seals! Having said that they were not passing oil.


You want to be careful not to mark the machined faces that mate directly to the machined gearbox faces




Here is a telling sight, a small piece of the cable loom (which I know I broke off on removal) which I am not overly concerned about as I checked the cable loom still clipped in place and it did. Im just happy I found the broken piece for removal!



This bridge seal for the pressurised oil supply to the valve body is also prone to becoming brittle and cracking causing failure (loss of pressure). On close inspection this one was good, however I had ordered one in advance just in case (Available from ZF or Audi - its the same part - ZF code 501.216.013 ; Audi code 09E 325 443A) so I will be refitting the new one and putting this 'used but good' one into stock