Sticking solenoid or something more sinister?

[marv8]

Had a gearbox rebuild (new clutch packs, drum and a few other bits and bobs) and new TC (apparently uprated) due to the dreaded 17125 a while back and box seemed fine. However after a few miles it started to thud in to 4th on upshift only. Spoken to the garage and they said give it a few miles as the TCU will need to "re-learn" shifts given the new parts. Gave it a few more miles and no better, then started intermittently thudding in to second as well so car went back to garage.
No fault codes apparently but took off valvebody and checked solenoids, tried switching a couple over to see if it was a duff one - got car back today and no change

Guy at garage is sure it must be solenoid issue as everything in the box has been checked and/or replaced. ATF came out clean and TQ locking up but just getting a bit concerned. Not being of a mechanical mind does this sound like it would/could be a solenoid issue? Should it not be throwing up a fault code? And is it the same solenoid or combination of solenoids for 2nd and 4th?

Any ideas appreciated - oh and they did warranty the gearbox for 12 months so needs to be perfect!

Cheers

[RS6Steve]

Does sound like a valve body sticking. It is a series of channels, balls and valves.

Get the box unto temp to the TC locks up and then go for some spirited driving changing manually up and down through the gears. See if that clears it.. They can stick quite easily if the ATF is not fully circulated!

Just my 2P, sure someone else will have a brighter idea

[Shoppinit]

In this report, the valvebody was stripped and serviced by ZF. Looks like they uprate some parts.

http://www.bimmerboard.com/forums/posts/527361

[marv8]

Thanks for your thoughts, just hope the solenoids are the answer. Those pics look familiar as when they rebuilt mr box it was stripped to individual components, put through the hotwash/giant dishwasher.
I know when the rebuild pack came from zf one of the clutch packs only had 3 plates in and mine had 5 I think? I believe when the garage checked with zf they agreed that 5 was a later upgrade to the box.
Everything that came out of the box was cleaned, checked and replaced if it showed any damage (burnt spots on clutch packs etc). All the replaced parts were measured to ensure they all matched.

Frustrating but getting used to that with the 6!

[paulcrake]

Hmmm... had similar work done to my box and they replaced the valvebody, why I don't know, but it was replaced along with clutch packs etc. It's always tricky having an auto trans rebuild and it only takes one bit of <beep> in the valvebody and you have problems. I wouldn't be risking it, insist on having the valvebody taken out and cleaned again...

[marv8]

Hopefully have this sorted by tomorrow - full solenoid pack being fitted and will ensure the check over the valve body.
They took some advice from another company who have rebuilt a number of boxes. They said they replace all solenoids after a rebuild, guess it only takes one moody one and guess when the box has been stripped and washed a bit of swarf could always get in there somehow!

[Shoppinit]

Cool. Let's hope that sorts it.

How come you didn't go for a recon box from ZF?

[marv8]

New solenoid pack fitted same old problem! Still bumps in to 4th, bumps in to 2nd occasionally when cold! Driving me mad but guess it's just another joy of RS ownership!
I did no go for the zf re con box as it was done under warranty and current box only covered 6k miles! Work under warranty but still a royal pain in the arse!
On the brighter side just got back from 150 mile drive home, had some fun with a porker Carrara s en route and proud to say the old girl held her own. Was on the motorway and speed was in to 3 digits but the rate these things put on speed is phenomenal think the porker driver was somewhat suprised!

[JCviggen]

Maybe its worth re-setting the TCU (starving it of power) and see how it feels after that...if the problem is there still right away, only after some learning, or maybe gone. Not much effort to try I guess.

[Shoppinit]

Sounds like a pain They must have screwed something up. Are they transmission specialists?

I know when the rebuild pack came from zf one of the clutch packs only had 3 plates in and mine had 5 I think? I believe when the garage checked with zf they agreed that 5 was a later upgrade to the box.

The box was never upgraded. The RS6 uses a similar box to other 5HP24A, but with uprated components. I can't help feeling that they are telling you little porkies.

[Shoppinit]

Maybe its worth re-setting the TCU (starving it of power) and see how it feels after that...if the problem is there still right away, only after some learning, or maybe gone. Not much effort to try I guess.

Frustratingly, removing power to the TCU doesn't reset anything. It must save stuff to non volatile memory. The only method I know of resetting the TCU is asking Audi to do it. I would be interested in finding another method. I have a spare TCU and it stores stuff in its memory for months.

[JCviggen]

That's annoying (Wonder whats the technical benefit of that) it still must be updated every now and then, no point to have a learning box computer if it keeps going on stuff it learned 8 years ago.

[Shoppinit]

It is. I think they have to flash it back to factory setting to reset it. However, the box adapts continuously.

All it's doing is learning how agressively you drive the car and stores this as a value between 0 and 255. Presumably 0 meaning you are overly cautious and 255 meaning you are Mooch.

You can read this value with the Vagcom: 'Driving style factor - required for calculation of driving dynamics index'

I'm pretty sure the only thing that it changes is how quickly it locks the torque converter up. Obviously the faster is locks up the converter, the more it stresses it. If you have a relaxed driving style, the TC lockup clutch will be lethargic and presumably last longer.

Hmm. Might be worth checking the driving style factor with the Vagcom before buying an RS6

[JCviggen]

255 meaning you are Mooch.

Maybe a power-off could still clear some relevant data even if it does not change the DSF. I definitely noticed the TCU struggling after the box rebuild with the battery disconnected. Whether it was the 2 week power-off or the new box components is not possible to determine but if it is adapting continuously I think there is a good chance it'd start from zero after a power off. The operational values that it is able to change by itself within a certain window must be somewhere, the DSF could be completely seperate?

[Shoppinit]

I have just read this extremely interesting thread about the adaptive behaviour of the 5HP24 - albeit the range rover version. There is also a method for resetting the TCU memory which I am now itching to try.

I wonder if this applies to Marv8's case. If RRPhil is correct (and he certainly sounds like he knows his stuff) then the box is learning and adapting all the time, not to driving style necessarily, but to wear of box components; varying the current to the solenoids to maintain a given pressure. Maybe a TCU reset would sort out marv8's rough gear changes as it seems to have done in these threads:

http://www.rangerovers.net/forum/viewto ... =2&t=41330 (very interesting, bit technical

http://www.rangerovers.net/forum/viewto ... 5&p=274154