Hi,
I have an XJ8 X350 4.2 Sport (2003), my car is not automatically shifting from 4th to 5th to 6th unless I am going at high speed; i.e it eventually shifts at high revs through 4th, 5th and into 6th at about 90MPH. I can manually force the change up my moving the lever to left in the 'J' gate and then back to automatic. If the box is in 6th and I accelrate hard from say 75 to 100MPH it kciks down fine but doesn't change back up unless I back off then increase speed again.

The gearbox is not in 'sport' mode (at least the light is off!) ....

The dealer has fitted a reconditioned box, torque converter, new trans fluid, a new J Gate and wiring harness there is nothing showing up in the diagnostics yet the problem still exists.

the box is silky smooth, no whines, noises, bangs, lurches or slugishness etc ...

The dealer is running out of options and Jaguar Tech Support haven't been helpful.... They are going to reflash the eprom later today but don't think that will fix it as they've done it when they installed the reconditioned box.

Any pointers would be greatly appreociated, I'm hoping that this can be fixed

Many thanks
Wes

 

If it changes OK at 90 mph but not at (say) 50, then the speed input to the ASM could be wrong.

I am very surprised you have spent so much on this problem without a diagnosis or cure.

 

Fraser,
Thanks for your response; thankfully the dealer agreed they were at fault fitting thr recon gearbox before completing the diagnostics so they are now footing the bill.

I'll ask the about the speed input into the ASM what ever that is.

I'll post updates on here; hopefully it can be resolved soon.

Best wishes
Wes

 

From what I have read in at least two Jaguar forums, problems and issues with the X350 gearbox are almost all caused by software and electronics.

I think the only mechanical fault I have seen was the torque converter lock-up clutch wearing out prematurely.

 

Hi Fraser,
The dealer is going to check the ECU's for water damage and reflash the gearbox. I'm hoping that a S/W refesh cures the problem. If it doesn't then they are going to have to look at the sensors.

I'm keeping my fingers crossed that they can fix it, otherwise I'll be needing a new car.

Cheers,
Wes

 

Hi Folks,
I've just had an update from the engineer:

The tranmission is now automatically changing through the gears up to and including 6th at the correct RPM. All the software on the car has been reprogrammed to the latest 2012 release from Jaguar.

The current persistent problem is on kick down it changes down to 3rd or 4th and stays there. The throttle response becomes very agreesive once it's kicked down. You can manually force the changes back up through the box into 6th but it won't do it automatically after kickdown.

I have the following questions:
1) could this be a fault in the kickdown mechanism
2) could it be an issue with the throttle position sensor
3) could it be a speed sensor

Does anyone have the following:

1) flow chart for the software and sensor chain and correct feedback voltages/currents

The deealer is waiting for ZF to coe back to them

needless to say there are NO errors being logged; the transmission passes all the reset self checks ...

Any ideas would be really well received! As always I'll keep you updated as to the progress.

Many thanks
Wes

 

I am assuming by "kickdown", you mean a driver full throttle application, rather than a change down on part throttle. However, it would be beneficial if you could give more description of the symptoms such as part throttle changes, (OK or not ?)

Anyway, lets get thinking..........

Consider a full throttle kickdown - with this, the box changes down to an allowed lowest ratio for the current speed such as to provide max acceleration. Lower ratios are barred (in the software ??) due to engine/transmission damage possibilities - engine over-rev, wheel lock, diff damage etc So at a very low speed with car maybe in 3rd, , kickdown would select 1 or 2, whereas at 40 mph, one would expect 3 as the minimum, and at 80 mph, probably only 5th, maybe 4th.

Car now shoots forward for an overtake (say). At a certain point, even if the throttle stays on the floor, an upchange should occur as the road speed for the ASM selected ratio gets up to the max of range This max will normally be max revs for the engine to avoid damage. Difficult to test on our crowded roads.

When the driver backs off the throttle, the box should return to a (higher) ratio mapped to the speed and throttle position. Note also that throttle movement (or rate of change), is also a factor.

On the old Borg-Warner boxes, there was something called a "kickdown" cable, which was taken off the throttle cable and was used to drive the kickdown, as well as allow the box to function in terms of oil pressure to the brake bands. A mechanical interlock prevented too low a gear from being selected. This is not provided on modern boxes, the gear inhibition comes from processing of electronic signals to the ASM via the CAN bus and these are, according to the Technical Notes: -

- throttle pedal position
- gear selector position (!)
- engine torque and revs
- trans fluid temperature
- brake pedal status
- engine oil temperature
- engine coolant temperature
- road wheel speed

I'm not sure why the gear selector position is listed as via the CAN bus as this has a cable connection to the box.

So, FWIW it looks on the face of it, to me, as if the problem lies outside the box. The solenoid valves to switch between gears are all working as the box changes up/down 1 through 6 at the right speeds as your dealer says. Anyway, as you said, it is a replacement box, so all should be OK internally.

I can't help but come back to the throttle pedal position but if this was duff, one would surely expect engine response problems too. Do you have any of these ?
It therefore could be related to engine revs input or road speed. However, there are two components in the box called (1) the turbine speed sensor, <torque converter>, and (2) the output speed sensor. It is not clear how these are used by the ASM as well as the list above.

You say it sticks in 3rd or 4th after kickdown, and you can only manually get it to change up. How are you doing this, across the 5, 4 or 3. then back to Drive ?

Interesting that there are no fault codes, indicating the ASM thinks everything is tikkety-boo !!

My best wishes to you for a diagnosis and cure !! Other thing is to look back and think of anything that happened recently to the car. Any work done on it for instance ?

 

Good monring Frasser,
By kickdown I mean when you are cruising and you put yout foot down on the accelerator quite hard the transmission changes down to 4th and then stays thier unles you move the J Gate lever from 'D' across to thr leftleave it for a second or two then move back to the right 'D' if it has gone down to 4th you have to reprat the procedurte again.

If you allow the car to coast and automatically change down due to RPM & roadspeed and then pick up the speed it changes up gears correctly to and including 6th.

Under gentle acceleration or hard acceleration it now changes up to 6th at the correct RPM. The unusual transmission upshift behaviour only coocurs after kickdown.

Thanks for your input :-)

I have the ZF6HP26 Technicians Diagnostic Guide if you want me to email it, it's 13MB in size.

Regards,
Wes

 

I forgot to add this behaviour is only occuring at motorway speeds, on 'A' road < 50mph the kickdown and return to 4th is working fine. It's only at speeds >50MPH.

 

the only recent work carried out is as follows:

1) 4 new break disc rotors & full set of pads
2) 4 Pirelli tyres (the same fit and model that has been on the car since new)
3) rear right swing arm replaced with gennuine new Jag part due to a worn bush
4) 80,000 mile service

 

Sorry, I should also have asked in relation to the list of recent work, when the problem appeared.

Anyway, what we now know is that the problem occurs: -

- with box in Drive
- speed > 50 mph

Your workaround is to move J-gate to '5' thus inhibiting '6' then moving back to Drive following which, box selects the expected ratio of '6' as normal. Hmmm.........

It is very difficult trying to work out a prognosis without knowing the ASM program features. Could you send the file you have please, 13Mb is OK, as I am on BT Infinity. I will have a look-see.

This must be a real PITA for you !!

Any other anomalies even small ones ?

 

Fraser,
I can't send you a private email on the forum with the diagnostics guide.

There are no other anomalies on the car.

Still waiting, but I have decided to move the car on and replace it with somthing else.

Best wishes,
Wes