2

Vehicles:

  • 1996 Dodge Intrepid, 350,000km, 3.3L V6, 4-speed automatic
  • 2000 Ford Windstar, 168,000km, 3.8L V6, 4-speed automatic

Symptoms:

I've seen this on 2 vehicles now (the 2 above). When slowing down for a stop, after I've shifted the automatic back into neutral (yes, I'm one of those weirdos who shifts his automatic into neutral while stopping), I hear and feel a single "thunk" sound when the vehicle speed drops bellow about 10-15 km/h. It does it very predictably, it's done it for a long long time on the Intrepid, a Windstar just came under my care for 1 week and it's doing it too.

If I didn't know any better, I'd say it felt like the tranny disengaging, but the tranny is in neutral at this point, what could it be? It feels like something big and heavy being retracted.

Update #1

Took the Intrepid out for a short drive and found the following:

  • the thunk only happens when coming to a stop in Neutral
  • the thunk never happens when coming to a stop in Drive
  • the thunk always happens exactly at 15 km/h (10 mph), while slowing down

Update #2

Posted this question over at DodgeIntrepid.net and got some interesting responses. Basically, 2 people were able to replicate this on their 1st-gen Intrepids, and one of them on their Jeep as well. That Jeep has a manual mode, and from fooling around with it, he suggests it's the transmission shifting into 1st gear (even though I'm in neutral). It was also suggested that it's the torque converter disengaging.

I feel both these answers are iffy, but is someone intimately familiar with the inner workings of this specific transmission (Chrysler's 42LE)? Could it be clutch packs doing something?

  • 1
    The transmission may be in neutral, but it is still being driven by the drivetrain as the vehicle slows. Sensors and/or valves are likely actuating and with the drop in pressure from the torque converter, it might make more noise than normal. Does it make these sounds if you leave it in gear and allow it to act normal? – CharlieRB Oct 17 '17 at 18:25
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    Also, don't shift into neutral when coming to a stop. – JPhi1618 Oct 17 '17 at 18:39
  • @CharlieRB I'll give it a try next time I drive the Intrepid – tlhIngan Oct 17 '17 at 20:16
  • @JPhi1618 Why not shift into neutral when coming to a stop? – tlhIngan Oct 17 '17 at 20:17
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    Because there's no reason to do it. It takes your attention at a time when that is very important, and it leaves the car unpowered if you need to accelerate for some reason. It can use more fuel because the engine has to run at idle rather than being kept running by the drivetrain. Some jurisdictions have laws against coasting in neutral on a downgrade. There's just not a reason I can think of to coast in neutral in an automatic. – JPhi1618 Oct 17 '17 at 20:27

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