dhob
Date Registered: 09-2009
TOTAL POSTS: 11
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Auto trans - momentary locking of rear diff?
Hi there
I've had a browse through the forum and can't really find anything on this.
Our X-Trail is the first 4WD and first auto we've had. I would have preferred to have got a manual but just not any around. I am finding various things happening with the way the auto shifts and I'm hugely suspicious that the 4WD system is doing things also (separate to my control) - damned fiendish electronic systems, you think you're in control but you discover that really the ECU and PCM are... and its fly by wire throttle too...
In general the X-Trail drives fine, shifts are good etc, but I have experienced a few times now a kind of abrupt slap or jolt which seems to be from the rear, even though the selection switch is in 2WD mode. Its just momentary, and not a major bang or anything. It occurred again today on the way home, in slow moving traffic on the motorway - approx 20 km/h, in Drive (O/D OFF), and hardly any throttle obviously.
I have seen in some tech info that even in 2WD mode the computer can select 4WD in certain conditions, so am wondering if this is whats happening. Is it possible that what I am noticing is the rear diff coupling locking or something? And if so, should it be doing this?
Anyone able to shed any light on this? - thanks for helping.
Cheers - Derek
--- Derek
2005 X-Trail
2.0 litre QR20 engine
Auto Trans
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1/Sep/2009, 6:15 pm
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jalalski
Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 29100
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Re: Auto trans - momentary locking of rear diff?
I agree with Rich and I think what you have experienced is the auto gearbox trying to shift just at the same moment when you applied the brakes in slow moving traffic. It happened to me as well and it has nothing to do with the rear diff engaging, as it would only engage in 2WD more if you accelerate hard at WOT.
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1/Sep/2009, 7:06 pm
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jalalski
Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 29100
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Re: Auto trans - momentary locking of rear diff?
Yes, definitely a clunk can be heard when this happens.
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1/Sep/2009, 7:58 pm
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jalalski
Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 29100
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Re: Auto trans - momentary locking of rear diff?
Derek,
My explanation to this is that the clunk actually happens at the front in the transfer case however it resonates the sound down the propeller shaft that is why it gives you the impression that it's coming from the rear diff, which obviously this shaft connects to.
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1/Sep/2009, 8:40 pm
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