Strange transmission - jerking/clunking at low speed

[zikomo]

XC90 MY10 2.4 D5 115k miles

At slow speeds, end especially when reversing, the car seems to "grab" a couple of times almost like gear is being engaged then unengaged then engaged again. Feels like a bit of a clunk. This only happens at very slow speeds. And more so in reverse than drive. Car drives perfectly in all other ways, except I am starting to suspect it is holding on to gears longer than it used to. I started to monitor fuel consumption and last 150 miles is averaging 29 mpg, quite a bit lower than normal. This might be unconnected as I have had a swirl arm fault, and suspect the swirls might be open all the time (I plan to investigate/fix this shortly).

VIDA shows no fault codes currently.

I have recently replaced a blown haldex pump (plus fluid and filter), following which I tested that AWD was working. Not sure if this is related, but a bit suspicious that inactive AWD caused by the blown pump may have been disguising other problems (maybe collar sleeve/angle gear).

Any advice on what to test/investigate? Hard to know where to start! Transmission fluid has never been changed so might try starting with that anyway. Thanks in advance!

[S60D5-185]

Originally Posted by zikomo

XC90 MY10 2.4 D5 115k miles

At slow speeds, end especially when reversing, the car seems to "grab" a couple of times almost like gear is being engaged then unengaged then engaged again. Feels like a bit of a clunk. This only happens at very slow speeds. And more so in reverse than drive. Car drives perfectly in all other ways, except I am starting to suspect it is holding on to gears longer than it used to. I started to monitor fuel consumption and last 150 miles is averaging 29 mpg, quite a bit lower than normal. This might be unconnected as I have had a swirl arm fault, and suspect the swirls might be open all the time (I plan to investigate/fix this shortly).

VIDA shows no fault codes currently.

I have recently replaced a blown haldex pump (plus fluid and filter), following which I tested that AWD was working. Not sure if this is related, but a bit suspicious that inactive AWD caused by the blown pump may have been disguising other problems (maybe collar sleeve/angle gear).

Any advice on what to test/investigate? Hard to know where to start! Transmission fluid has never been changed so might try starting with that anyway. Thanks in advance!

100 per cent that is the correct place to start. plenty of info on here as to what is involved.👍

[zikomo]

Thanks I will definitely change the transmission fluid. That said I am pretty sure the sensation is coming from the back so suspect it is something in the rear drive causing the problem. As I said it is suspicious that the problem only started to manifest after fixing the haldex pump, no AWD may well have been disguising it.

Anyone else have any thoughts?

[owenfackrell]

To test the idea that no AWD was masking the issue you could unplug it and then test the car. As you have VIDA you can reset an error codes.

[zikomo]

Originally Posted by owenfackrell

To test the idea that no AWD was masking the issue you could unplug it and then test the car. As you have VIDA you can reset an error codes.

Thanks thats a good idea I will give it a go and see what happens.

[zikomo]

Still no closer to establishing the cause. And somewhat flumoxed by no fault codes showing...