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Strange banging/flapping noise 400 mi after transmission fluid/filter change

7K views 6 replies 5 participants last post by  tcwagner1 
#1 · (Edited)
A strange banging/flapping noise developed about 400 miles after getting the transmission fluid and filter replaced in my 1998 Dodge Grand Caravan SE Sport with the 3.8 V6 engine and front wheel drive. The odometer currently reads 62,544 miles (about 100,655 kilometers). The noise seems to only happen while driving at any speed and taking my foot off the accelerator, probably while the automatic transmission puts itself in neutral. The frequency of the banging/flapping noise is increased as the speed of the minivan is increased.

We are the original owners of our minivan. We've had the transmission fluid and filter replaced at roughly 15,000 mile (about 24,140 km) intervals. I've always stood in the Dodge, Chrysler, or Plymouth dealer's service garage door area to watch and make sure they do things correctly such as really drain the fluid, really replace the filter, use the ATF+3 or ATF+4 fluid when refilling, and so on. This last time I used an independent garage and everything seemed okay. The only thing I could not see was the brand of the filter as it was in a clear bag rather than in a labeled box.

Any ideas what this might be? After driving, parking on level ground, and with the engine still running I checked the transmission fluid level and it is slightly higher than halfway between the two marks - maybe short 1/3 of a US liquid quart (about 0.3 liters). My guesses are the transmission is "complaining" because the transmission fluid is not exactly at the full mark, the mechanic might not have firmly pushed the new transmission filter all the way into place and is slightly loose, an aftermarket transmission filter might have been used, or maybe something else is wrong with my minivan that is not related to this recent transmission fluid and filter replacement - such as a foreign object is stuck somewhere in the engine bay or front wheel area. For whatever it is worth there aren't any transmission fluid drip stains on the ground under the minivan. I will buy a bottle of ATF+4 transmission fluid and bring the fluid level all the way to the full mark, but I have doubts as to this being the cause of the occasional banging/flapping noise.

Although my wife and I don't drive our minivan as often as most people drive theirs, we do enjoy our minivan and want to keep it easily another 10 years. I've done the oil changes, wheel rotations, and coolant/antifreeze changes myself but left the other maintenance things to the mechanics - perhaps sooner than recommended by the maintenance schedule in the owners manual. We're concerned about this and want to get it fixed before something bad could happen to our minivan.

I joined this forum years ago and periodically read the postings. Today this is my first post to the forum. Thanks in advance for any and all replies!
 
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#3 ·
As AirBoss has mentioned, check the serpentine belt, but also check your CV boots. You may have torn one.

If you're still under warranty, stop by the dealer and have them ride with you to hear it.

Stick with the ATF4 :ThumbsUp:

Keep us informed :thumb:
 
#4 ·
Thanks for the tips. Sorry for the delay; I was waiting for decent weather before proceeding with my minivan.

Okay all the CV boots looked fine. The serpentine belt tensioner was actually chirping/squealing a little bit so I replaced it. The chirping/squealing is now gone. Partial success! :beerchug:

Now for the bad news. The original banging/flapping noise is still there, heard when taking my foot off the accelerator. So my next stop is the Dodge dealer for diagnosis and repair. The warranty expired long ago so I'll have to surrender my credit card. :angry:

By the way I am not upset about replacing the serpentine belt tensioner because a search of this forum shows the chirping/squealing indicated it was starting to fail. The 15mm nut on the rear of the belt tensioner was impossible to loosen. Eventually I sprayed PB Blaster and then the nut finally loosened. Getting the serpentine belt back on was a bit challenging too. :cool:
 
#5 ·
Now for the bad news. The original banging/flapping noise is still there, heard when taking my foot off the accelerator. So my next stop is the Dodge dealer for diagnosis and repair. The warranty expired long ago so I'll have to surrender my credit card. :angry:
I forgot to update. The noise was a wobbling brake rotor.

Before going to the dealer I guessed the problem might have been something with the front brakes such as a stuck caliper slide pin or a loose brake pad. When I prepared to examine the brakes I discovered on the driver's side one of the lug nuts was missing, the lug stud with the missing lug nut sheared off leaving half behind, and the other four lug nuts were all loose.

I replaced the lug stud and the lug nut. I bought them at my local Advance Auto Parts store; the prices were very low. It was something like $1.50 for the lug stud. The price of the lug nut(s) I can't recall but the price was very reasonable.

I removed the brake caliper and rotor, turned the wheel - I guess it was the hub - so the broken lug stud lined up with nothing behind it, sprayed the broken lug stud with Liquid Wrench, and then tapped the broken lug stud repeatedly with a small hammer until it fell out. I put the new lug stud in as best I could, put a lug nut on, and tightened the lug nut to draw the lug stud into place. Then I removed the lug nut, put the brake rotor and caliper back into place, tightening the bolts to spec. Next I put the wheel back on and tightened the 5 lug nuts to 100 ft-lbs. Then for safe measure I loosened and re-torqued the lug nuts on the other three wheels. By the way none of them were loose.

I did a test drive and from that point since the banging/flapping noise problem was solved. No visit to the Dodge dealer was needed.

This leaves the question of how did the lug nuts on this one wheel got loosened. It turned out to be a case of neighborhood vandalism. While walking my dog I began noticing quite a few vehicles parked in driveways that were missing one or two lug nuts from a wheel. Jeez, when I was a teenager we'd buy the cheapest toilet paper and go decorate trees. Times certainly are different today!
 
#6 ·
I would say to maybe replace the other wheel studs on that hub that was loose. When lug nuts come loose and the wheel wobbles, it tends to stretch the lug studs and the nuts may come loose again. If you notice that they come loose it means that the stud is stretching and going to fail.
 
#7 ·
I would verify with the independent shop that replaced your filter that they used only ATF4, not a generic with an additive. If they did, change it again, replace the filter with one from the Dodge dealer, it is not much more, 9$ or so, and reuse a rubber gasket for your pan from NAPA so you can do your own changes, inspections easy. You can reuse it for years with many up and downs. Change your oil a few times to get all the generic out if that is what they used, to preserve what is left of your tranny.
 
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