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
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Derek
2005 X-Trail
2.0 litre QR20 engine
Auto Trans
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1/Sep/2009, 7:15 pm
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Re: Auto trans - momentary locking of rear diff?
Hi Derek and welcome to the forum.
You'd be doing well to be able to detect when the rear is engaged, especially when in 2WD mode. Probably the only time the rear is engaged when in 2WD mode is under full throttle from stand-still, which from what you've described, isn't the way you're driving it when you notice it.
What it could be (and has been mentioned in other threads) is that you may happen to back-off the throttle just as the auto box decides to change up a gear, giving you a surging/lurching feeling (search for "surge" in the forum).
Other than that, there may be something wrong somewhere, or it could be some other issue.
I presume you've double-checked it's not in 4WD-LOCK mode.
--- Rich. X-013(c)
'04 S2 ST Auto. Nudge_roofracks_tow_tints_Lightforce_GME_BFG_TBS_home-made-bashplate_50mm-spacer-lift
Click here to see >300MB of photos and videos All For His Glory. |
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1/Sep/2009, 7:54 pm
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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, 8:06 pm
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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, 8:58 pm
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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, 9:40 pm
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Re: Auto trans - momentary locking of rear diff?
Hi Derek,
Reading your first post on this thread, is there a reason you are travelling with the overdrive off? I leave mine on all the time unless towing?
Vic
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2003 Auto STR X'Trail with Hyper Roof Rail
Vic (X-139) WA
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4/Sep/2009, 12:36 am
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