2006 XJ at152k miles, I have done the trans fluid+pan changes at 60k and 120k with OE ZF fluid and parts. Also did the bridge and tube seals at the 120k fluid change. Recently (within the last year/10k miles, not exactly sure when) I noticed the 5-6 and 6-5 shifts with a thud. It's not a huge bang, and it's not a slip shift. If you are driving on a bumpy road you wouldn't even feel it. It's just noticeable to me because the 5-6 shift has always been imperceptible.

Does this sound like something that a valve body rebuild would fix? In Googling around, I see a lot of posts on the BMW forums that solenoids are known to go bad, cause poor shifts, etc. I also ran across the Sonnax Zip Kit which has a lot of modified parts claiming to resolve issues with wear-n-tear in the valve body. I do also have the issue of a slow engagement from park to R... it's often 3-5 seconds to engage reverse on a cold start. I'm 99% sure the VB rebuild would fix this issue, but not sure about the 5-6 thud. If that sounds like there's deeper problems it may not be worth spending the $500 on parts for this. Other than that the shifts are all the same as they have been since the car was nearly new.

I did take a look in the TCM live data, but none of the PIDs seem relevant. I tried 2 scan tools (not SDD) that claim OEM level of diagnostic, only get 32 data PIDs. There are data points for the solenoid driver current, but no data on line pressures or anything like that. Is this something that SDD provides? Or is it a special ZF tool?

Thanks,
Michael

 

I would CLEAR ADAPTATIONS before touching the mechanical part of the gearbox.

Plenty of info on software issues over the years.

Lots of TSBs on various faults remedied by reprogramming/clearing.

 

Rear wheel speed sensors or reluctor rings any codes? Or dsc abs speedcontrol restricted perf. Messages?
also coils to sparkplugs .
otherwise check for oil leak trans cooler lines esp. Behind radiator and connector sleeve
120k is nothing for tranny 230k on v8
check oil lvel procedure again
Tranny would after oilchange and rubber changes be totally capable of updating the new pressure loss or gain and do the adaptations on its own
If all of this is ok. Where could a mistake been made.
if no leak . Do level procedure again. Oil slightely dripping, car leveled , running engine, go through J gate with foot on brake , oil temp between 40 and 50 celsius . Correct level close filler hole.
but I guess you know

 

I could definitely see the adaptations being a cause for the 5-6 shift thud, but I really doubt they are responsible for the park-reverse delay. I could try resetting them and see what happens. Is there any risk of doing this if I don't replace parts first? I recall reading here someone reset the adapts and then the trans would not learn one or more shifts. Had to get an entire trans rebuild.

I can try checking the oil level. There are no leaks and the trans was normal for several years after the last oil change/rubber part refresh.

No codes in any module, no ABS issues, no misfires. Everything is running as normal as it always has minus the 5-6 shift thud. Just took a 1000 mile road trip and the car returned 31 mpg.

I guess I'm a bit confused--if you look on the BMW or RangeRover forums all they talk about is solenoids failing in the 6HP series. This is not a common issue for this transmission?

The other thing that may be a good option, instead of going with the Sonnax Zip Kit that modifies a ton of parts in the valve body, I remember M539 on YT doing just the solenoids and accumulators in his 6HP28 (along with the bridge and tube seals). This fixed his reverse delay, though he did not have any other shifting issues. This seems like more of the option I would lean toward--just replacing the wear components with OEM. Not try and start making modifications.

Edit: I had to get out my maintenance log and take a look at what years/mileages the work was done. I did do a radiator replacement in 2022, and at the time I captured any oil that came out of the cooler (less than 1 oz) so I saw no need to check the trans level. May indeed be worth a double check. Unless there was somehow a lot of fluid trapped in there that I didn't know about, the fluid level should not have changed.

3/8/2020 - 133,547 miles - trans service including bridge and tube seals
8/20/22 - 141,039 miles - radiator replacement (OEM)
1/2023 - 143k
1/2024 - 146k
1/2025 - 150k
Presently at 152,000 miles. I would estimate the 5-6 shift issue has developed in the last year/2k miles. There was no issue with the 5-6 shift for several year and at least 5k miles after doing the radiator. Hard to say for sure when I first noticed it, I do a lot of driving < 40 mph lately and wouldn't have even gotten into 6th gear.

 

I was the driver while my friend next to me did the life data and drive cycle giving me instructions how to proceed ,reading what to do on SDD for the tranny drive cycle on his tdvi x358 .
during the drive cycle there is lots of procedures like accel. Up to 80km/h keeping for 15 secends then coasting without braking down to 40km/h and keeping it there 15 seconds till the green light appeared " accomplished.
the initiated drive cycle will help the tranny to readjust pressures needed to shift and will show the pressures needed for the different clutches ,
max pressure is about 750 millibar.
as soon as you reach that level it can't go any higher but... the change of bridgeseal and tubes can regain some of it due to better sealing , preventing pressure loss.
mean while other places (considering mileage) like the main shaft seals inside the tranny could be worn and the shaft getting wiggely ... this would need a referb.
5 and 6 are rarely prone to failure , but can cause clunks when rear wheel speed sensors are giving up. I had that reluctor ring with a dent. When I accelerated hard with kick down then released accelerator pedal at 130km/h I got that hard clunk.
3and 4 are the most likely to cause trouble

then the valvebody and mecatronic has very thin seals inside between plates and also rubberparts with tiny springs insdes the different canals.
JUst changing the solenoids next ? Hm ok if that does not help then I guess it is best to see a specialist

 

I need to pull out the laptop with SDD and have a look around. Does it let you view current adaptation values? I saw this on a BMW forum and it pointed to potential issues where one adaptation was off the charts high.

Agree, it could just be worn out transmission at this mileage. My only hope is that because it's a hard shift, not a slip shift, that it's more of a control issue and not leaking internally at the clutch apply piston.

Last question: can the trans pan and connector sleeve be re-used if they only have 17k miles on them? I think the FSM says discard the pan every time you remove it? Maybe I'm confusing that with something else.

Edit - I ran across this video on YT today. Very similar symptoms: 2004 BMW with 6HP26, slow to engage reverse and hard shifting in upper gears. Trans shop replaced the dampers and solenoids, reset adaptations. So it looks like this may be on the right track! I'll start ordering parts and figure out how to determine the correct separator plate.

 

I watched Ferraro a couple of times. There's a german Video Don Simon for the Zf 6hp26 " wie funktioniert der Scheiss"
I would change the pan and connector sleeve again from Zf . While at it with the sleeve , I remember reading of oil has leaked into the electric plug . Don't know if it is possible to see inside

 

Agree, I'll include the pan and sleeve when I do it. The oil is too expensive to waste doing this another time.

Is it necessary to replace the bridge and tubes any time the mechatronic is dropped out? Or are those okay to reuse?

 

The initial idea and necessity was those parts did not well with the oil esp.early models where bridgeseal deteriorated that much the developped fissures a lost a lot of pressure. So no I would leave them in.
the pan is a different story you could put ift back but if it is leaking after 100miles you would start again.
single pan here is about 80€ today on autodoc
usy around a 100

 

You do know that Mercon SP is identical to Lifeguard6 and is much easier and cheaper to get?
I am a fan of the Sonnex kit but that's up to you.

I have never seen a ZF that did not leak thru the sleeve where the wire connections attach. It's cheap and can only be changed with the pan off so a perfect time to do when changing fluids. Note the different O-rings on the replacement sleeve.

I have recommended the CTSC for a number of years. They are stone cold ZF experts!
If you need anything or have questions take a look.
ZF Parts
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Definitely--I've used CTSC for all my ZF transmission parts.

Was looking at their site this morning to estimate pricing--the bridge and tube seals are an additional $40, but considering I just replaced them, will leave them alone. Pan kit with sleeve $260, solenoids $300, separator plate $100, dampers $12, shipping and handling. So probably $750-800 to do the job.

I need to read the 1068 number off the side of the transmission to get the correct pieces, conveniently (not!) the shift cable bracket is directly in front of it... *sigh*

 

I'd start with a fluid check and top off, and clear adapts with SDD. But, given your car's mileage, it may be time to dive into the valve body, doing solenoids at minimum.

I went down this whole trail 4 1/2 years/nearly 100k miles ago on my '04, right around 145k miles. A few months after buying the car I started experiencing flare shifts 2-3 and 5-6, but it was going into gear just fine. Did the usual pan/fluid and seals change (Mercon SP), with no differences made. The car had previously had fluid changed around 70k. Did lots of reading online, both here in the forum and elsewhere. Probably the best article I read on the topic was: https://www.bavlogic.com/?p=3738 . Finally bit the bullet, ordered a new set of solenoids and a ZIP Kit from Rock, and sourced the correct spacer plate semi-locally and in-person from a transmission parts supplier. Sonnax's instructions are excellent, but still, take lots of photos during disassembly and don't drop any of the little *****! Also, your valve body may have a different number of check ***** than what the instructions indicate.

Did the full job in the garage at home with front of the car on ramps and the back on stands to level the car. Refilled, reset adapts and haven't needed to go back into the transmission since, other than one ATF and pan change/adapt reset, about a year/25k miles ago. I'm now at 241k miles, and it's still shifting and driving nicely.

Paul

 

If you have used CTSC then you are on the right track.
241K is impressive too.

Also 10-4 on those little *****!!
Here is the transmission tag as mentioned above.




This is critical to get the right parts.
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Great info, thank you! So you did the entire Zip kit and not just the solenoids and dampers? Was that the kit which changes all the valves and changes the dampers from the OE style to the piston/spring type?

I'm still debating whether I should do a Zip kit or just the OE replacement dampers + solenoids.

 

I ordered and did the full ZIP kit (or awfully close, anyway). I think there were a few of the bits of the kit that I didn't install--probably a couple end plugs that fought me, IIRC. To clubairth1's previous comment, I didn't buy the bits from CTSC, but from RockAuto (solenoids were genuine ZF, too). At the time, the local Ford dealer's parts counter was the cheapest source for Mercon SP (Advance Auto Parts stocked it as well), and the separator plate came from a transmission parts vendor who is a stocking Sonnax dealer, located about 45 minutes' drive from me.

Paul

 

that is the same kit i used. Very easy to install. Noticed crisper shifts with no clunk at all. Those dampers make a difference. When i separated the valve body i made sure to have it flipped to have the check ***** on the bottom portion then made a small witness mark with a center punch next to the ball indent on the valve body. 2 marks for the spring things. Use 300 grit wet/dry sandpaper to clean seperator plate residue and rinse and dry before reassymbly of valve body. Should be good to go

 

Yes when I take any valve body off I sand it lightly. I have glued a piece of sandpaper to a small pane of flat glass which is mounted on a wood board. I figure making sure the valve body is dead flat is worthwhile.
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Good advice, thank you all for the comments.

Still struggling to read the ID tag... I guess there are numbers on there? Yikes. I'll have to get under there better and probably remove the shift bracket to get something readable.

 

If you're trying to ID the separator plate between the halves of the valve body, you'll need to proceed with dropping the pan.

Here's what the tag on the separator plate will look like in-car:


And, here's a chart showing what separator plate you'll need to obtain, based on the ZF part number on the tag:



Hope this helps,
Paul

 

Thanks Paul! Learn new stuff everyday. I did not know there was another metal tag inside the transmission.
Have had pans off a number of times and just never saw that.
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