04, 4.4 v8 petrol.
After a few minutes it goes into trans fail safe mode, I have recently had gearbox oil and filter changed to cure rumble.
Reading some previous posts people mention cooling issues, mine does lose water. Would a diagnostic say what the issue is or just give a list of possibles. Should I get a new rad and take it from there.
Thanks.

Is your transfer box working correctly? That’s how my issues started on my last car.
Try shifting from high to low and back two or three times. 2017 Jaguar F Pace 25t Portfolio - still part of the JLR family 😀
2009 3.6 V8 (MY2010) - my first ever diesel! - now also gone
2004 4.4 V8 Petrol Vogue - now gone

Do you get any other issues at the same time like suspension inactive?

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Simon
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When you’re in failsafe mode, does Reverse still work fine? Does the transmission operation return to normal once the fluid has cooled down but then go back into failsafe around 15 minutes after starting from cold? Does your transmission lock in 5th gear rather than 4th gear when failsafe is engaged, and also engage drive with a bit of a thump when selecting Drive from Neutral?

Phil

Doesnt seem to be any other issues, suspension ok but will check tomorrow , no noise from drive to neutral, how would I check if it's stuck in 4th or 5th. Goes into fail safe after a couple of miles, will be normal again after a few hours parked.
I don't have a hand book so not sure if I can check oil levels from menu or have to do it manually.

Reverse is fine, suspension goes up and down maybe a little slow and i can hear pump working
After a few minutes as I accelerated there was a thump then fail safe came on, neutral to drive I get a slight thump. Don’t know if it’s in 4 or 5 but at 50mph revs we’re at 2250, anything else I can do to help diagnose problem. Thanks

I appreciate that, because the torque converter lock-up clutch is automatically disengaged in failsafe mode, it can be hard to distinguish between 4th and 5th gears just from the engine revs.

The reason this is important, though, is because it identifies if the fault lies with the transmission’s A-clutch. The transmission would normally failsafe into 4th gear (A & B clutches applied). The A-clutch is used in 1st, 2nd, 3rd & 4th gears so, if there is an issue with the A-clutch, the transmission has to failsafe into 5th gear instead (B & D clutches applied). The problem you are describing sounds exactly like a particular axial bearing has failed in your transmission, but this would cause the transmission to failsafe into 5th and not 4th.

4th is geared at 23.7mph/1000rpm and 5th at 29.5mph/1000rpm so, at 50mph, the input shaft turns at 2110rpm in 4th and in 5th at 1695rpm. Because of the slip across the converter (& the inaccuracy of the speedo) the engine speed won’t quite match these figures but you should be able to get close providing that you’re neither in a drive nor an overrun condition. You just need to get the throttle positioned so that the vehicle is coasting.

Phil

Thanks will take it down the dual carriageway tomorrow and determine what is what. If the problem is as you suspect what would need to be done and ballpark cost, ( I appretiate cost is dependant on who does it)
Thanks for sharing your knowledge.

If it’s the axial bearing/O-ring issue, and you’re handy with a set of spanners, then potentially you could repair it yourself quite cheaply, but with an element of risk. If you drop the transmission and only remove the A & B clutch assembly to replace the bearing and O-ring then the chances are that you’d get away with it with just £70 worth of parts.

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Thanks, going to take it for a run and try and confirm what gear it's stuck in.

Took it down long flat lane, at 1000rpm it hovered around 20 mph or a tad over, drove a few hundred mtrs and it was constant at that speed.

Unfortunately, the difference between engine speeds in 4th and 5th only becomes apparent at higher vehicle speeds. So, for example, at 60mph 4th gear is equivalent to around 2500rpm and 5th gear would be 2000rpm, so the 500rpm difference should be apparent on the rev counter.

As previously discussed, moving the throttle between drive and overrun, even at constant vehicle speed, will cause the engine speed to change significantly because the torque converter is unlocked, so finding the ‘coast’ condition where you are neither accelerating nor decelerating is a bit tricky.

Phil

Thanks will take it out again later and check at 60mph, I guess there isn’t a sure fire way of checking.