Hello folks; today, after putting some petrol in the thing; my X308 XJR decided it wanted to snap my neck, not from the torque of the motor, but by the transmission doing a shift from 1st to 2nd gear that I can only describe as a 10 on the Richter Scale. After this; the car shifted from 2nd to 3rd completely normally, and when I came to a stoplight and set off again, it shifted completely normally from 1st to 2nd and hasn't tried to split continents since.

Side note; the vehicle did not have the sport button engaged, yet it was using the shift points from the sport mode (i.e. shifting at 3k RPM as opposed to the regular 2k or 1.5k RPM)

Is there any known cause for this? Perhaps a fault with the transmission control module, or maybe even something else entirely? As of right now; I am unsure.

 

I occasionally get the same thing and have been searching the archives for an answer. Do you have a camera shutter like noise when the cars idling? I do, seems to be related.

What I've found so far is that there's a known issue with the transmission electrical connector and low fluid levels. You can check fluid level with a dipstick from for around $7, mine was delivered earlier this week and I'll be checking the level this weekend. I haven't gotten very far with researching this but flush and replace both the filter and a new connector seem to be where I'm headed.

Here's a couple of related links
https://www.jaguarforums.com/forum/x...siness-245378/
https://www.jaguarforums.com/forum/x...ncerned-33677/
DIY Replace Transmission Connector Adapter Plug O-rings Mercedes Benz 722.6 ? MB Medic

 

I've checked the car for said shuttering sound, and all that I can really hear is the normal clicking of the powers that be inside the engine compartment upon startup, besides that; no camera shutter sound.

My lucky guess is that it would be something to do with the electronics, I know that Jag electrics have always been pretty hairy, but the Ford era cars are somewhat more robust. A mix of Mercedes, Jag and Ford doesn't seem to have blended too well in this case.

Another theory that my girlfriend came up with it that the gears in the transmission were binding somehow, although I do find that highly unlikely; you never know.

 

Do not push the engine to get it to shift as you explore this

 

I would perform a hard reset myself but, here’s an alternative. Highorse forwarded me this link.

http://www.mercedesmedic.com/reset-m...-instructions/

 

is your 13 pin leaking or your conductor plate could be toast too

 

Following because I've been getting hard shifting 1-2, 2-3 and downshifts there as well, ever since I've gotten my replacement transmission. May try the kickdown switch method, after I verify my switch is working, may have damaged the wires on it messing around with it when I first got the car.

I've also noticed I get the shutter noise from the transmission pan when idling. Very important detail though, it only happens when sport mode is disabled. If sport mode is enabled, no shutter noise. I replaced the electrical connector, verified fluid levels the proper MB way when I got the transmission, so those shouldn't be a cause. I haven't seen any codes, but from experience I know these transmissions can be bricked and putting the engine into limp mode, without throwing a P-code.

 

Hey everybody, I bought my 2001 xj8 dirt cheap because the transmission was blown. It did what you described. A neck snapping shift from 1st to 2nd. I of course had to have it rebuilt. I knew this before I bought it. Here is what the mechanic told me about the transmission. American transmissions from the big 3 ( Ford,Chrysler, and GM), use a high pressure high volume operating system for the valve body. The fluid that flows through it is at a high pressure and there is a lot of it. Pros and cons to this system is when the valve body begins to wear from age as all transmission valve bodies do, there is more than enough fluid to compensate for any decrease in shifting performance. The downside is the shifting is not as refined as our cars. The naturally aspirated XJ8's and the XJR use german transmissions as we know, ZF for the XJ8 and Mercedes for the XJR. They use a low pressure low volume system. There is high pressure fluid in the system but is is regulated down in pressure before it is sent to the valve body. Pros to this are very smooth, quick, crisp shifts. Down sides are proper maintenance is critical, changing the fluid on time! If the fluid is not changed on time it can cause premature wear in the pressure regulating valve allowing high pressure fluid to flow were it is not supposed to. The first warning sign is a prolonged pause before the transmission engages first gear. Normally it should take no longer than 1 or 1-1/2 seconds. Second warning sign is the neck snapping jerk you mentioned. After this the next thing is the transmission will break the 1st and 2nd gear drum. This is what happened to mine. I would strongly advise you to have the car towed to a transmission specialist who specializes in the German transmissions, such as an independent Mercedes or BMW specialist. They would be able to tell you if there is a problem with the valve body or not. If there is not a problem with the valve body and the problem is electronic at least would have the peace of mind knowing that the valve body is ok. And just to let everybody know who may not know this already, the transmission fluid should be changed at approx 50,000 miles. You will not find this in the owners manual since jaguar says that the transmission is a "sealed for life unit and does not normally require service". The catch is the "does not NORMALLY require service"part. The transmission does not need to be serviced "normally", that is until the fluid needs to be changed. The dealers of course know this and when the first owner of the car brings it in for say the 50,000 or 60,000 mile service that's when they would probably change the fluid and send the owner down the road with the fluid changed and the transmission good to go for another 50,000+ miles. I hope this helps, and good luck.

 

Checked fluid level today and it's a little over full, up to the top of the plastic part of the dipstick. The fluid's got 60k miles on it and brown, presume it should be red, time for a change. I hadn't noticed that the shutter noise only happens when not in sport but can confirm that's true for me too, interesting! Attachment has the sound.

I had one hard shift driving around today. Drove to the store and all was fine. Got in car to drive home and I can tell it's going to happen as the car seems to be engine braking more rather than coasting driving around the parking lot. Pulling out on to a main road had a hard shift from 1-2. I'd noticed the same thing last time it happened.

I'm not getting any other hard shifts other than 1-2 and no delay going into first. It only seems to happen once in a days driving too and not every time, I'm not certain but I think it's just the first restart after getting the car up to temperature.

The connectors cheap enough that it's worth replacing if I'm going to be under the car changing the fluid and filter. The posts on the Mercedes sites suggest it's difficult to get the new one in place. Anyone have that problem?

Also, any way to tell if the conductor plate is toast?

Thanks
Mike

 

lube the o-rings push it all the way in bolt it down

impossible to screw up

 

Have you done the relearn procedure that I posted above? It will literally only cost you like 2 minutes of your time and “may” fix the issue??

 

Not yet but I will, worth trying next time I drive the car.

I can see how reprogramming the shift points would help if the car was consistently shifting late, just not sure that it'll help with an occasional hard shift. 99.9% of the time it's shifting fine, just occasionally it won't shift up into second till it hits close to 4k. When it happened to my wife, she said it was like someone had driven into the back of the car the jolt was so severe.

 

Mine too. Long story short, get your fluid changed at minimum. To rebuild a ZF transmission is an occasional thing, but it is not pleasant. Think $3-4k. So not stratospheric, but also not pocket change.

 

Keep in mind that, in the case of the MB transmission, the Jag Workshop Manual states that any "excess of fluid MUST be removed".

 

Right on with the $3-4K for a rebuild. Mine was $3k.

 

Any updates on whether or not a rebuild is necessary or if it just needed a new connector? I have the same problem going on with mine right now. 2001 xjr with the Mercedes transmission and it will ocasionally do a hard shift from 1st to 2nd and it clicks when its idling and warm and will stop if I put it into sport mode.

 

probably the connector

sometimes the tcm is damaged from wicking

 

Did the reset procedure Addicted2Boost recommended and it hasn't reoccurred since but it was fairly infrequent for me and I've only driven a couple of hundred miles since then. Clicking/shutter sound on idle is still there.

I'm not ready to declare success yet but I'm optimistic.

 

fix the connector

failure rate is 100%

 

Second @xalty - I had a trans coolant leak from an otherwise leak-free car with 80k on it, then it started acting wonky between 1-2 shifts. As you've got the XJR, go to your local Mercedes dealer for the parts, the 722.6 is a very common transmission and they'll very likely have all parts in stock. Where the local Jag dealer in Memphis wanted something obscene like $400+ for parts before adding in fluid, the local Merc dealer had everything in stock, including fluid, out the door for less than $120 - connector, seals, filter and fluid.