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Disco 2 V8 Autobox has D drive,3,2,1 but R reverse dosn't work


James NZ

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Hi all,

I've just been away and arrived home, reversed the truck up the driveway and parked it up. The day after I needed to move it and it wouldn't engage reverse gear, it will drive forward no problems. So I checked the ATF level and that's all good. I went for a quick drive down the street and back and forward motion seems normal but I still don't have reverse. Absolutely nothing happens when you shift into reverse. So I put the Nanocom on, there are no faults showing (except for the oxy sensors again), the M&S lights are not flashing. The shift indicator lights on the console and dash light up correctly with no flashing. So I thought maybe a a dirty plug for the xyz switch or maybe the switch itself.

I took the xyz switch off today and opened it up thinking it might be dirty wiper contacts but mine seems different to the ones I've read about online. I've included pictures of the xyz switch as well, it seemed quite clean to me. I did think with the river crossings that it might have had water inside, but there wasn't. I've since sprayed it with contact cleaner/lube. I've also checked the loom and can't find any obvious faults. The shifter works as it should.

It also had Maxlife atf auto fluid change (4 times) and filter approx 5k km ago. Its been driving fine since then.

Does anyone have any ideas what may be the problem?

Thanks, James NZ

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The XYZ switch shouldn't affect anything but the forward gear selection. P/R/N/D are still actuated mechanically.

If you want to be sure of this, unplug the ECU and try to drive.

A fault will only be logged if the output is different enough from the expected output. So probably at extended higher revs.

From your symptoms I'd guess something failed in the reverse clutch or valving.

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Thanks for the reply elbekko. I was starting to reach the same conclusion. I was actually going to be selling the disco after this last trip away, until this happened. As the car sat around unused for 2020 I'm thinking maybe the valve block gummed up a bit, although the flushing out and new filters would off helped I thought. I'm hoping it is the MV valve, so I will be removing the valve block and checking the MV valves.

I also found a Jaguar official "ZF Automatic Transmission Service Manual" for the 4HP22 & 24E and it has a handy fault chart. The faults for no reverse are - dirty oil filter, jammed governor, jammed reverse inhibit valve (which is MV2) or low oil level.

 

Cheers, James NZ

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