Ahoy there Disco-ers,
I have a Discovery 3 here in australia that has been smooth driving since we got a few years back, but now we are having a strange issue with the ZF6HP trans that im wondering if i could get some guidance on.
So what happens is we can drive all day every day around town with no issues, but then i get out onto the highway and up to a speed where im in 6th gear (100kph here is oz) and if the car has to load up to keep going the 100kmh speed limit when going up a hill, sometimes there will be a small jolt, the car will drop down a gear and I get a "Transmission Fault" message. The car still drives fine and will change happily through all the gears from 1-5 as per normal but it wont change up to 6th and i also lose the ability to command shift. Turning the car off resets whatever the issue is and i can get 6th gear again. After it did it the first time I did a trans fluid change and it seemed to have fixed/hidden the issue for a while but its back happening again with only about 5000kms on the new fluid.
Ive done a search and cant seem to find anything exactly the same as my issue as i dont get put into a limp mode or anything, just no 6th gear.
One possible cause i found with was the rubber gaskets on top of the mechatronics in the box, does my fault sound like that could be a cause?
If my gearbox is dying, is it as simple as sourcing another zf and bolting it on or does landrover use a volvo like system where only 1 engine and box can be ever be together?

Anyhow thanks in advance for any info,
Trent

 

Need codes or its all guess work. But lets guess anyway. The valve body seals onto the valve body generally cause harsher shifts as they harden but they don't normally cause faults. In your case, the fault is likely happening first and results in harsh shifts. Modern transmissions tend to shift harshly when in fault mode to reduce the risk of slipping clutches which can result in possible damage but more importantly generate heat. So quick shifts are thought to be best when there is an issue.

As for swapping, I think you can swap any replacement trans just fine but it must be encoded for the truck. With no way to do so, you must care the metrics unit over. I could be wrong since I never had to do this but I think that is what I recall being said.

 

TDV6/V6 or V8, each has its own specific box and no other will interchange. Another same engine box can be fitted by either swapping the valvebody/machatronic unit or reflashing the trans ECU.