6 Speed box, jolt on 5 to 4 downshift

[Graham-XKR]

Hi, I've just joined and can't find this specific problem elsewhere, sorry its long but these bits might be relevant.

I just bought a 2005 XKR 4.2-S Supercharged Coupe with 110k on the clock. It's tidy, and with a good service history but no record of a gearbox oil change.

It drives well except that it jumps when put into Drive from Neutral, and jolts on the downshift from 5 to 4 (but not any other) and that jolt is less noticeable or goes away altogether if I'm braking hardish when it happens (around 40mph). Reading comments on here and general transmission related advice on other forums I arranged to have the transmission flushed (autotron machine) and resulting Oil/Filter/Sump change.

Maybe related: on a longer run, we drove about 100 miles and stopped for 15 minutes, then set off again, after about another 20 miles 'Restricted Performance' flagged up, fortunately we only had ~5 miles to go. The following day noticed it flashed up 'DSC System Failure' before starting. two days later, did a similar long run, stopped for 10 mins after about 80 miles, drove another 40, 'Restricted Performance', drove last 5 miles and the following day the engine warning light stayed on, but the car then drove ok 3 miles to the Transmission Centre.

They said the Garage said the gearbox seemed healthy, no metal filings or anything nasty in the old oil. They also did a code scan and said there were NO Transmission fault codes, just loads and loads of others, which have now been cleared.

The transmission now seems even smoother and quieter than before, but the two problems still persist.

The Transmission centre don't have the facility to update the software or to reset and recalibrate the box, suggested I look for engine or electrical problems first and then take it to a Jag Specialist if it continues, so its now booked in with the garage I always use to have everything checked over, they'll tell me if I need a Jag specialist or not.

Does anyone have any thoughts as to what might cause this specific problem ? I have checked the battery - it's showing 12.3 Volts standing, 14.4 Volts charging. is that slightly low voltage enough to cause a problem ?

thanks,

Graham

[Astromorg]

The fluid change was definitely the right way to go for the harsh drive engagement and 3-4 change.

Low battery voltage does create a great number of obscure fault codes that the average scanner is not able to read. They seldom include any to worry about!

A software re-flash might help, though I'm not sure there have been any software updates for the final year models. I've had mine since 2008 and it's never been done! The memory/calibration for the gearbox is held in the transmission control module (TCM) that shouldn't be affected by a fluid change. If the battery has been disconnected, this is Jaguar's advice to follow after reconnecting:

Connect the battery ground cable.Tighten to 4 Nm.
Turn the ignition switch to the ON position. Cycle both door drop glasses up and down to establish the upper and lower datum points.
Lower the glass to the stop and hold the switch in the DOWN position for a further five seconds.
Raise the glass fully and hold the switch in the UP position for a further five seconds.

Start the engine and allow to idle until the engine reaches normal operating temperature.Switch the engine off.
Start the engine and allow to idle for approximately two minutes (this will allow the ECM to learn the idle values).
Apply and hold the brake pedal, select drive and allow the engine to idle for a further two minutes.
Drive the vehicle for approximately five miles/eight kilometers of varied driving to enable the ECM to complete its learning strategy.

Reset the audio unit, clock and climate control assembly to preferred settings

The charging voltage of 14.4 is fine (It will vary according to temperature and battery condition), but 12.3 is not good, though it depends when it was taken. Immediately after a good run it should be nearer, or more than, 13 dropping away as surface charge on the plates dispels until after about 12 hours when it should still be somewhere between 12.6 and 12.8. The 12 hour wait can be 'replicated' by turning on the headlights for 5 minutes.Then check voltage.

A DSC warning while cranking the engine is a definite sign of a low battery voltage, as are problems with the windows misbehaving!

[Graham-XKR]

Thanks Astromorg,

I saw the car 2 weeks ago, and picked it up on the Saturday. Previous owner barely used it - I've done more miles in 2 weeks than it did in previous 2 years while he had it. I don't know whether the battery remained charged during that two years, it could well have been flat at some time.

Sounds like disconnecting the battery, and performing the reset procedure would be a good start. I've also had a suggestion to give the battery a full charge overnight, so will combine the two, full charge, disconnect, then reset and relearn.

I'll report back in a day or two !

oh, any idea if there should be a vent connected to the battery and where that vent pipe might be ? The Battery does appear to have one.

[Astromorg]

Yes there should be a battery vent at the front end of the battery The tube leads into the corner of the boot where there are two grommets. One is a blank and the other has the vent tube running through it.

Sorry, but given that probable history, I don't hold out any hope of that battery giving you any reliable service!

[Graham-XKR]

Thanks, I'll have a look!

[RichardSEL]

My last XJ8 had an OEM battery in the boot
But no docs to show when it was installed.
There was no date code on it
-- unlike Varta for example that have manufactured year and month embossed (conveniently) on the underside of the case in a time clock format:

Stencil rubbings of '16MY Varta 800AHC

In January of this year, that battery showed as less than ¼ life remaining with a terminal voltage off load after car not being run for 24 hours of only 12.3V Varta Blue range offers a four year life

[Graham-XKR]

Thanks, looks like I might need a new battery then, BUT I'll get the calibration on my tester checked first, just in case.

I tested my BMW too, that's been doing strange things and the battery is showing 12.2v after standing - it's only a year old so I will see if I can get it replaced.

[Graham-XKR]

Update: After overnight charge (on my new Smart Charger!) Voltage was up to 12.6,went out for a run of about 20 miles, and it was up to 12.8.

"DSC System Failure" message hasn't come up again, but one window lowered itself part way when I locked it !

I have now put a charging connector in the boot so I can hook the charger up quickly whenever it's parked at home. I'll see if battery recovers further before shelling out for a new one.

Haven't tried a disconnect and reset yet, that's next.

[Graham-XKR]

Further update, Battery still isn't holding above 12.6, and that with the charger on whenever I'm not driving it., so time for a new battery I think; Any recommendations Lead Acid or Gel, particular brands ? I've seen a Bosch Silver 100Ah for@£130, with 6 year guaranty.

Graham

[mike020150]

If it helps and tempting fate, my Varta branded battery on an intermittently used classic is now 9 years of age. That came with a 3 year warranty so 6 years sounds even more attractive. Mike.

[poprivet]

Re. battery suppliers, consider Tayna. Many here including myself have used them and were pleased.

https://www.tayna.co.uk/car-batteries/

Al

[Graham-XKR]

Thanks, just ordered from Tayna - slight glitch in the order process but I'll sort it !

[Graham-XKR]

An Update: Problem Fixed!!!

I replaced the battery, doing a hard reset at the same time. On removal discovered that the old battery was distorted at one end, so in a way I've probably been lucky it had been holding charge at all.

I went through the hard reset procedure, as detailed elsewhere in here, and while everything worked as before the gearbox problem also persisted.

So, earlier this week I contacted the North Staffs JEC branch to see if their was a local Jaguar specialist they could recommend. Mike Beirne from the branch got back to me alomst immediately andf pointed me to AWJ Automotive, Jaguar Specialists in Newcastle-Under-Lyme. I explained the pronblem to them and booked it in for a Diagnostics check today (Friday) before teeing up the Warranty Company in case it was mechanical.

This morning I took it over to AWJ who ran diagnostics and confirmed there were no fault codes stored, but confirmed the problem on a test drive on a test drive. They then reset the gearbox adaptions, retested and it's fixed ! Just have to drive it steady for a 100 miles or so while it relearns how to do stuff.

Very impressed with AWJ, friendly people, had a cup of coffee and a chat about cars while I waited, and 90 minutes later it only cost me £99, which I don't think is bad at all.

Next job is to get the underside cleaned off, re-sealed and treated which AWJ can also do apparently.

[mike020150]

Just time left to enjoy the car for the remainder of what passes as a UK summer. Mike.