Gearbox Teardown & Refurbish - 6HP28A61

[ATinOf]

The old gals coming up to 72K now and still running strong, (touch wood) this refurb has stood the test of time, another 5K and it will be time for a fluid change.
I really should get round to finishing the commentary on those last images and posting a parts list/costing, if only I could find the time.....

[welwynnick]

This is a really great thread. To the OP - did you find the cause of the original problem (stuck in fifth) when you were stripping and rebuilding?

Second - the title says your box is a 6HP28A61. I thought the C6 RS6 had the 6HP26A61. That's quite a big change. The second generation 6HP boxes had quicker changes and slightly more torque capacity.

This got me wondering if the 6HP28A61 was an improvement late in the model cycle, and something worth looking out for? What model year was your car?

Do you know if your torque converter or TCU were any different to other RS6 units?

Thanks, Nick

PS. For those that don't know, the 26 and the 28 refer to the input shaft diameter in mm, and the input shaft is one of the weak links in the 6HP26A61 (plus I got the impression that changes weren't that quick). "Weak link" is being a bit unfair, as the stock box seems to cope with tuning pretty well.

[ATinOf]

- did you find the cause of the original problem (stuck in fifth) when you were stripping and rebuilding?
- the title says your box is a 6HP28A61. I thought the C6 RS6 had the 6HP26A61. That's quite a big change. The second generation 6HP boxes had quicker changes and slightly more torque capacity.

For those really observant there is an image in one of these posts (third in this link viewtopic.php?f=47&t=129779#p894614 ) that shows the ZF tag with model and serial number stamped - This is on the underside of the box and tells you what the code is. Check yours and advise if its diifferent. I believe all C6 RS6 are 6HP28's but Im sure someone will correct me if this is not the case. Mine is a 2008.

I put my sticking gear down to one of 2 (or both) main problems found; loss of pressure at the valve body seals (compressed rubber tubes) and bad clutch stack clearances.

[c3nturi0n]

slightly topic related... is there an indicator or oil level stick like on ZF's to determine the amount / level of oil in them?

[ATinOf]

No means of visually checking box level; you have to follow the procedure which is remove the filler plug run the car to get the box to temp (as seen in VCDS) and top up till it spills over the edge of the filler plug. Clearly the car has to be LEVEL.

Top of my head I cant recall the temp limits for this check but 36-38 rings a bell. I can check ELSA if you need it

[c3nturi0n]

No means of visually checking box level; you have to follow the procedure which is remove the filler plug run the car to get the box to temp (as seen in VCDS) and top up till it spills over the edge of the filler plug. Clearly the car has to be LEVEL.

Top of my head I cant recall the temp limits for this check but 36-38 rings a bell. I can check ELSA if you need it

cheers AT... that'd be great if you could please.

[ATinOf]

Thank IanH for the OP - one of these.....

viewtopic.php?f=47&t=119322&p=784972&hi ... ox#p784972

level is correct with spillage from filler plug at 35-40 temp;

[welwynnick]

- did you find the cause of the original problem (stuck in fifth) when you were stripping and rebuilding?
- the title says your box is a 6HP28A61. I thought the C6 RS6 had the 6HP26A61. That's quite a big change. The second generation 6HP boxes had quicker changes and slightly more torque capacity.

For those really observant there is an image in one of these posts (third in this link viewtopic.php?f=47&t=129779#p894614 ) that shows the ZF tag with model and serial number stamped - This is on the underside of the box and tells you what the code is. Check yours and advise if its diifferent. I believe all C6 RS6 are 6HP28's but Im sure someone will correct me if this is not the case. Mine is a 2008.

ATinOf, thanks for all your input.

[don0301]

- did you find the cause of the original problem (stuck in fifth) when you were stripping and rebuilding?
- the title says your box is a 6HP28A61. I thought the C6 RS6 had the 6HP26A61. That's quite a big change. The second generation 6HP boxes had quicker changes and slightly more torque capacity.

For those really observant there is an image in one of these posts (third in this link viewtopic.php?f=47&t=129779#p894614 ) that shows the ZF tag with model and serial number stamped - This is on the underside of the box and tells you what the code is. Check yours and advise if its diifferent. I believe all C6 RS6 are 6HP28's but Im sure someone will correct me if this is not the case. Mine is a 2008.

I put my sticking gear down to one of 2 (or both) main problems found; loss of pressure at the valve body seals (compressed rubber tubes) and bad clutch stack clearances.

He (welwynnick) doesn't own a C6 RS6, just endlessly talks sh1te about them.

[welwynnick]

He (welwynnick) doesn't own a C6 RS6, just endlessly talks sh1te about them.

Based on recent posts you've proved it's all evidence to the contrary.

[zex]

Great thread! Only problem now is that photos are no longer visible

I noticed clicking sound turning the wheels while parking or when I get of the throttle at slow speed. I managed to recreate this sound on the lifter. You can see (hear) it in this video (it actually doesn't sound this loud in real life):



I went to audi garage and they told me it's prop shaft but I'm not that convinced. Clicking/knocking sound is coming from the box just before prop shaft starts - connects.
ATinOf would probably know right away what could be the cause (is it in the gearbox or prop shaft or something else maybe ).

Thanks

[Jim Haseltine]

As I found to my cost about 18 months back, the front drive shaft inner cv joints have an amazing amount of free play even when new. Before I pulled the RH joint apart to replace it I expected it to be full of the usual black grease, especially as that was what was supplied in the new joint kit but no, when I took the cv boot off what ran out was watery brown oily stuff. The new joint stuffed full of the black grease had similar play to the old one but was a bit quieter when turning it manually.
Turned out the noise I was chasing wasn't mechanical, it was from a well camouflaged nail in a tyre.

[Stiggles]

Great thread! Only problem now is that photos are no longer visible

I noticed clicking sound turning the wheels while parking or when I get of the throttle at slow speed. I managed to recreate this sound on the lifter. You can see (hear) it in this video (it actually doesn't sound this loud in real life):



I went to audi garage and they told me it's prop shaft but I'm not that convinced. Clicking/knocking sound is coming from the box just before prop shaft starts - connects.
ATinOf would probably know right away what could be the cause (is it in the gearbox or prop shaft or something else maybe ).

Thanks

That sounds just like the noise I got from my prop, get it up on the lift and with a hand on the prop rotate it back and forth, the cables or whatever it is inside the propshaft had broken, the longer you leave it the noisier it'll get

I replaced my prop with one from bailey Morris as suggested by another member here and the supplied part was identical to the Audi one but around a third of the price of one through TPS

Mine was only noisy at low speed and turning, it had the carrier bearing replaced so definitely wasn't that

[zex]

Thanks
I found new prop shaft for around 800 eur. How much was yours?

[Stiggles]

Thanks
I found new prop shaft for around 800 eur. How much was yours?

Just checked was actually £673 so half the price of TPS, got the vat back which always helps lol

Works out about €800 so not much difference