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Powertrain Question

(1999 Ford Explorer)
in Milford, CT on June 15, 2010
I have a loud "bang" when I am driving. My mechanic, who I trust, seems to think either a transfer case or transmission issue. He is not sure which. The bang is starting to become more frequent. Not all the time. Driving straight or reverse. Low speed or higher speeds. It even happened once when I parked, put the car in "park" and turned off the engine. Someone suggested maybe one of the springs in the transfer case make be catching and then releasing. Thoughts? Repairable or replace?
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Popular Answer
on June 15, 2010
Try putting the transfer case in all of its phases i.e. 2wd high ( if available ), 4wd high and 4wd low and see if there is any change to the 'bang'. Be sure to check all of your drive shafts, axle shafts and CV joints for play and wear. I have seen u-joints and I have seen CV joints that are worn out, do this. I re-built transmissions in a Ford Dealerships for some years and don't remember an automatic trans ever doing this but I have seen and repaired manual transmissions for this and differentials for this. Put the car on a hoist and drive it while some one under neath listens. It should not be that hard to find the cause, since it is a loud bang, it sounds like a chipped gear tooth, and don't rule out the differentials!
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on June 16, 2010
Hi dandd,

The mechanic did put it up on the lift and try 2wd, 4wd, reverse etc. but could not recreate the "bang". They are hesitant to try 4wd under load as not to cause any unnecessary damage. FYI, there is no notable metal or shavings when the fluids are drained. I can drive for a half hour and not hear the noise BUT i can drive for 15 minutes and hear it 6 times. The car has no difficulty in steering and gas mileage is excellent. Also the "bang" does not really happen at highway speeds. Thoughts? Many thanks in advance.
on November 15, 2010
I also have this same issue and have checked a few things with no results. it seems to come from the rear passenger side. Any luck throw me some more things to check.
on November 15, 2010
It ended up being the transfer case. Had to take it apart and have a Ford tech look at it. Very little damage for the amount of noise it was making.
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