Newby here to the forum so please forgive any transgressions. My 2006 XJ8L ~185k miles transmission suddenly started bucking and slipping the day after a three hours trip to PA through heavy rain. NO troubles on the trip to or from. Also no troubles on the previous 5 hour trip to NY two weeks prior. scanner shows no codes but readings from the regulators and switches are erratic, between value and zero or active/inactive. I am foolishly hoping this is an electrical issue perhaps due to the rain. I am thinking perhaps the connector to the transmission got some water in somehow causing erratic electrical signals..does anyone have any thoughts. Having just broken down and put new tires and bilsteins along with all new front an rear control arms and hubs on, and replacing the sneaky valley coolant hose.. I can't handle giving up on this cat!

 

Check that the ECM isn't flooded first
Steve

 

will do with fingers crossed and report back

 

Update and more information. I checked the condition of the ECU. there does not appear to be a problem with water around the ECU. While sitting stationary in the lot, the car in drive or reverse, parking brake engaged, pressure on the brake pedal, scanner shows the gears changing from 1-4 randomly, with regulators and switches activating and deactivating randomly (seems random to me anyway) accompanied by the corresponding lurching with gear changes. An overnight rest and long warm-up the next day while I tried to get SDD program to load, eliminated the previously mentioned lurching while in drive but stationary. no clear signs of trans fluid leaking from pan/filter. next day, a quick trip down the street nearly left me stranded without forward gears, but moving the J shifter all the way to 2nd allowed a limp home only 1000yds away. only then did the TRANSMISSION FAULT show on the dash but without any code readable by my scanner (not SDD --which is still not working!!) back to luching while stationary.

 

Two things to check first:

• Condition of the battery, which should have a minimum of 12.6 volts across the terminals with the ignition off for at least ten minutes.
• Misfire(s) can cause similar 'lurching' when driving. Check to see if there is water or oil in the spark plug wells causing the coil unit(s) to short.

 

Battery is good, just replaced, holdng 12.8.(Father-in-law runs battery shop so new battery every two years...good deal if you can get it)
doubt the misfire, but I will of course check when time permits, scanner doesn't pick it up any misfire and there is a definite shifting issue when in motion, slipping, high revving and gear searching (at least on the last real road test it got anyway----i dare not drive it for further testing however given its behavior in the neighborhood).

the sudden change, from a very smooth purring tranny to chitty-chitty-bang-bang seems to suggest electrical problem to me as I would have expected more gradual increase in slipping from mechanical problem.

 

Misfires often don't set a DTC and turn on the MIL.

Check the electrical connector to the gearbox to see if there is water present.

Has the gearbox fluid level been checked? The procedure is outlined in the attached file.

 

Live data doesn't show a misfire, but I will check physically. We have put 45k miles on since we bought it and I have not changed the fluid. Was advised not to by local Jag shop as I had zero trouble with it until this. At 185K+ miles I figure I am at least in it for new filter and fluid....not afraid to do other things while I am there, but since I work on my back some things are more daunting than others. Don't like to replace things without reason, but sometimes being there already is reason enough.

 

There has been ocasional trouble with the bolts holding the transmission cable near where it goes into the gearbox coming loos or even dropping off. The cable movements are then not correct.

 

Contrary to what was previously stated by Jaguar, ZF now say the gearbox fluid and pan/filter should be changed every 60 thousand miles. Bear in mind that low fluid level can also cause erratic shifting and eventual failure of the clutches. Check the cooling lines for signs of leakage as that's often how the fluid level becomes low.

As Fraser mentioned above, check the two 10mm (M6 X 20mm) bolts securing the shift cable to gearbox as they have a tendency to work their way loose and should be checked during every engine oil change.

 

+1 fluid needs changing periodically - and Jaguar have said so for years on their Tech web site... (many shops appear not to read it!)

 

Thanks everyone ...I have plenty to check when the pavement clears of rain/snow. Sadly, as this is a long cat caging in the garage leaves no room to work.
I got a little more of the story yesterday from the Mrs. the extended drive north 3 hrs and back 4 hrs was uneventful other than the heavy rain on the return trip, UNTIL about one mile from the house where she encountered a large pool of water on the road causing a significant hydroplane event. Although the cat stayed composed as it should, it was the next drive cycle roughly 12 hours later that the symptoms started almost immediately.

 

Definitely no panic hurry and don't panic about it. The ZF 6HP26 is far more robust than sometimes thought.

Water may well be a contributing factor or indeed the real cause.

 

One of the first things i do is to change trans oil with filter, after purchase, not that hard and lets you see what shape it's in.

Seems that i also read water can get into the trans through a breather opening, but don't remember any thing more.

Point being, change the oil with filter in the trans to see if oil has water in it.

If so this should help to clear things up, if not & turns out to be another issue, no harm done in changing the oil & filter.

 

Chaos Update.
well things got quite strange with this 06 x350

I decided to source an xp laptop and V131.03 software to get into this trans issue. As the car had not been run in a few weeks give or take I went out one morning to start it up...and it did just fine. I went inside for a bit only to come back to a locked car...key in ignition..engine running. Second key in my wife's purse 30 miles away. Good news is it ran beautifully for the 30+ minutes it took for my annoyed wife to cut her shopping trip short and return home. Trans fault and parking brake fault and cruise disabled all taunting me from the dash.

A few days later, laptop charged and ready, I set out to cure this cat. As I sat in the drivers seat fumbling through the less than intuitive SDD program, engine running ..no lights at first, then an engine stumble, trans brake and cruise warnings returned, the doors locked and engine raced to well over 6000 rpm with no input from me and nothing I could do to settle her down other than turn off the key....#ChristineLives At this point I am thinking I may be outmatched and my limited knowledge has merely dug my hole deeper....as limited knowledge tends to do. Computer problems are not my thing...and this clearly is computer problem.... Perhaps I would be better served by an Aluminum Recycler!!!!

Another few days passed, my courage returned. I would try again. Again, Trans, Brake and cruise warnings, rough idle, locked doors but without the terrifying revving of a posessed cat. The SDD is useless....because the TCM doesn't exist according to it. I used an Autel 802 to find code P1605-- lost communication to TCM. Car still runs and goes into gear(s) but only schizophrenically. Back and forth between SDD and 802 and iCarsoft i930, but nothing will "talk" to TCM. Desparately I pressed the "?" button on the 802 with regard to the P1605 code. It suggested turning the key oft to on to off 6 times in a row without starting. Which I did. With a restart nothing happened at first, then the Nav screen suddenly displayed something like "Error! Consult your Dealer"--which I read as "Welcome to your deeper hole!". Turned the key off. started one more time. No warning lights, no locked doors, all the code readers recognize the TCM, a TCM that has no stored or pending DTCs.

A feeling of hope enveloped me, so I boldly set off on a test drive. First in the driveway....no troubles....then around the block....no troubles....then to the market and back no troubles. 30 mph, 50, 60, 85mph without trouble Do I feel more power from this cat now?! How can that be? The things I was planning to do (and still plan to do)....the pan/filter and fluid change and the sealing sleeve and mechatronic seals have not been done, the coils and plugs are as they were.....as far as I can tell it is back to pre-puddle form....with an off-on-off reset suggested rather inconspicuously by the Autel 802!. This is all for what it is worth to those that might travel this same road! Thanks forum!

 

Excellent news and thank you for describing your steps.

When time permits, please edit your post by adding paragraphs so it's easier for all to read and understand.

 

Thanks NBCat. I was lackadaisical with my formatting. It has been adjusted....for the better I hope, but admittedly far from polished or perfect.

 

Had a very similar issue at a stop, tranny trying to shift in and out sporadically. No mil until one day got communication error then finally misfire.
If you haven't changed your plugs and coils you might as well do it now. A bad coil can jolt the electrical system causing weird gremlins.

 

Thanks BlackKat sure enough number 6 coil was misfiring with no MIL, but showed up on scan tool. I only replaced the one coil because presently I fear putting more $ into this car without be certain it has a few lives left. After the coil swap, so far so good. It is still hard to accept that a single misfiring coil could have led to the transmission chaos that we experienced. If anyone has any thoughts on trans filter and fluid brands, i.e. ZF only or aftermarket acceptable...I still have that task ahead of me.

 

Steel pan, believe it's the Cobra trans filter, with Mercon SP fluid, is in both my transmissions.
No more leaks, neither one had any issues, except the old fluid, & filter were in need of changing.