Discussion
I am currently having a nightmare with my 98 V8 Sov (160k)
The gearbox started going very rough – lurching from gear to gear and not going into drive in May. I look it to a ZF specialist in Hayes and they diagnosed a clutch, which they replaced in a couple of days.
It seemed better but still the change from 5 to 4 was very rough – almost a bang as it dropped down. So I took it back and they replaced a valve, which made no difference, except it made it rough going into drive in the first place, though I was told this would go.
I took it back again and they said they had replaced it with a recon gearbox. They seemd decent people and have I no reason not to belive them but the problem is still ecactly the same. It can be recreated by manually shifting from drive to 4
Its almost fine going up the gears, though from cold it sometimes holds 3rd too long if I am going uphill) but going down to accelerate is very clunky if done smoothly. Oddly if you really boot it its fine
Wierdly the traction control, stability control and ABS warnings have also started coming on, which may or may not be linked
It is currently in a garage where they believe they have checked all sensors and etc
In the morning we are switching over the ECU and air flow meter to see if we can eliminate these.
Anyone experiences anything similar, or can offer any thoughts
Many thanks
James
These 5-speed auto gearboxes were first used by BMW in the early 90's, and they're electronically controlled by a gearbox ECU that's also linked to the main engine ECU.
Whilst I can't diagnose your exact fault, I can give you a brief run-down of how the system works.
The mechanical side of the gearbox has the usual epicyclic geartrains which are engaged/disengaged by multiplate clutches inside the gearbox and thus select the different ratios & reverse gear.
The multiplate clutches are engaged/disengaged by hydraulic fluid pressure that is controlled by small electric solenoid valves in the gearbox. The fluid pressure for the gearbox is generated by a hydraulic pump at the front of the autobox, driven by the engine.
The electric solenoid valves in the gearbox determine which multiplate clutches are pressurised and thus which gear is selected.
The solenoid valves are driven by the gearbox ECU, and it is this special ECU that determines which gear is selected. In much older autos it was done by a mechanical valve block inside the autobox.
The gearbox ECU needs to know 2 things to decide which gear to select-the vehicle road speed and the engine load.
Vehicle road speed on the ZF 5-speed ZF autoboxes is determined by an electrical sensor in the gearbox rear that measures the rotational speed of the autobox output shaft, ie the propshaft speed. This sensor sends it's signal to the gearbox ECU.
Engine load is usually measured by a potentiometer/variable resisistor fitted to the thottle body, and this develops a voltage related to the accelerator pedal position and hence engine load. This sensor also sends it's signal to the gearbox ECU.
So it's the gearbox ECU that decides which gear to be in, and the the gearbox itself that does the mechanical selection.
One known fault is wear and tear on the throttle potentiometer on the throttle body, which gives intermittent/unsteady/wrong voltages to the gearbox ECU and confuses it, causing inconsistent gear selection.
Also, the engine ECU is also linked to the gearbox ECU, as the gearbox ECU tells the engine ECU to retard the engine ignition timing momentarily when changing gear, in order to give a smoother gear change.
The fact that you mention ABS and traction lights coming on point to an electrical glitch somewhere, and it may not be the gearbox at all causing the trouble.
An engine fault may cause erratic gearbox shifting, and a faulty engine management sensor may not allow the gearbox ECU to control the engine ECU and retard the ignition timing during gearshifts, as the engine may be in 'limp-home' mode and unresponsive to anything else.
If the gearbox electrics go faulty then the gearbox enters it's own 'limp home' mode, selects 4th gear, and lights the 'gearbox fault' lamp.
It may be your throttle body potentiometer or your gearbox ECU, or maybe even a simple relay fault somewhere, but it does sound like an electrical system fault with you mentioning the other warning lights illuminating.
Hope this helps
Alex
Whilst I can't diagnose your exact fault, I can give you a brief run-down of how the system works.
The mechanical side of the gearbox has the usual epicyclic geartrains which are engaged/disengaged by multiplate clutches inside the gearbox and thus select the different ratios & reverse gear.
The multiplate clutches are engaged/disengaged by hydraulic fluid pressure that is controlled by small electric solenoid valves in the gearbox. The fluid pressure for the gearbox is generated by a hydraulic pump at the front of the autobox, driven by the engine.
The electric solenoid valves in the gearbox determine which multiplate clutches are pressurised and thus which gear is selected.
The solenoid valves are driven by the gearbox ECU, and it is this special ECU that determines which gear is selected. In much older autos it was done by a mechanical valve block inside the autobox.
The gearbox ECU needs to know 2 things to decide which gear to select-the vehicle road speed and the engine load.
Vehicle road speed on the ZF 5-speed ZF autoboxes is determined by an electrical sensor in the gearbox rear that measures the rotational speed of the autobox output shaft, ie the propshaft speed. This sensor sends it's signal to the gearbox ECU.
Engine load is usually measured by a potentiometer/variable resisistor fitted to the thottle body, and this develops a voltage related to the accelerator pedal position and hence engine load. This sensor also sends it's signal to the gearbox ECU.
So it's the gearbox ECU that decides which gear to be in, and the the gearbox itself that does the mechanical selection.
One known fault is wear and tear on the throttle potentiometer on the throttle body, which gives intermittent/unsteady/wrong voltages to the gearbox ECU and confuses it, causing inconsistent gear selection.
Also, the engine ECU is also linked to the gearbox ECU, as the gearbox ECU tells the engine ECU to retard the engine ignition timing momentarily when changing gear, in order to give a smoother gear change.
The fact that you mention ABS and traction lights coming on point to an electrical glitch somewhere, and it may not be the gearbox at all causing the trouble.
An engine fault may cause erratic gearbox shifting, and a faulty engine management sensor may not allow the gearbox ECU to control the engine ECU and retard the ignition timing during gearshifts, as the engine may be in 'limp-home' mode and unresponsive to anything else.
If the gearbox electrics go faulty then the gearbox enters it's own 'limp home' mode, selects 4th gear, and lights the 'gearbox fault' lamp.
It may be your throttle body potentiometer or your gearbox ECU, or maybe even a simple relay fault somewhere, but it does sound like an electrical system fault with you mentioning the other warning lights illuminating.
Hope this helps
Alex
Best of luck! I've outlined the general system operation so there may be bits and pieces that are vehicle specific and unique to Jaguar that I've not mentioned-my experience was predominantly with the ZF 4-speed electronic autobox as fitted to BMW's, and the ZF 5-speed auto as fitted to my own BMW 540i.
From the BMW forums the only fault that seemed to crop up on the ZF 5-speed auto was a delay of a few seconds when selecting reverse.
It's the same autobox that's fitted to the V8 Jaguars though, although the more powerful V8 XJR had to be fitted with a Mercedes 5-speed electronically controlled auto to cope with the extra torque.
Being German autoboxes they usually follow a simliar logical path in layout/operation!
My own V12 X300 Daimler Double Six has a GM 4-speed electronic auto, so Jaguar certainly fitted a wide variety of autos to their various models.
You may be able to find more information by posting on the BMW forums and asking about the 5-speed ZF autos fitted to the V8 E34 5-series and V8 E32 7-series.
These were 'sealed for life' autos and you couldn't do a regular filter/autobox oil change, which many people though a retrograde step.
Alex
From the BMW forums the only fault that seemed to crop up on the ZF 5-speed auto was a delay of a few seconds when selecting reverse.
It's the same autobox that's fitted to the V8 Jaguars though, although the more powerful V8 XJR had to be fitted with a Mercedes 5-speed electronically controlled auto to cope with the extra torque.
Being German autoboxes they usually follow a simliar logical path in layout/operation!
My own V12 X300 Daimler Double Six has a GM 4-speed electronic auto, so Jaguar certainly fitted a wide variety of autos to their various models.
You may be able to find more information by posting on the BMW forums and asking about the 5-speed ZF autos fitted to the V8 E34 5-series and V8 E32 7-series.
These were 'sealed for life' autos and you couldn't do a regular filter/autobox oil change, which many people though a retrograde step.
Alex
If the car runs fine in 5th and has problems going into 4th; whilst having problems moving off the line then the A clutch is probably worn out.
The only way you are ever going to fix this is to use diagnosis tools to find out what is wrong and then fix it, swapping parts at random is going to waste a lot of money.
Fitting a rebuilt transmission also needs to include a flushing of the external hydraulics - i.e. pipes and cooler because to not do so will trash a new gearbox. The garage also needs to have the correct oil at the correct level. The rotary switch and gear cables also need to be correctly set.
The only way you are ever going to fix this is to use diagnosis tools to find out what is wrong and then fix it, swapping parts at random is going to waste a lot of money.
Fitting a rebuilt transmission also needs to include a flushing of the external hydraulics - i.e. pipes and cooler because to not do so will trash a new gearbox. The garage also needs to have the correct oil at the correct level. The rotary switch and gear cables also need to be correctly set.
Gassing Station | Jaguar | Top of Page | What's New | My Stuff