HI, i've got a 97 explorer xlt 5speed.... here is the problem...

when you start the truck and start driving... its making a Loud clunking noise from under the car... at first we thought it was the gear box but then after replacing with a reconditioned gearbox and transfer case it was still there... it is doing this in auto mode and in 4x4 mode... during city driving it does it all the time .... but when you drive it to 100km/h the clunking completely stops.... and then you can bring the car to a complete halt (without turning the engine off) and start driving again and the clunking is still gone... BUT as soon as you turn the engine off and on again (even if only for a minute) the clunking returns again until you drive to 100km/h and then it stops again.

HELP PLEASE

 

I moved you here ....more help then Gen Automotive

 

G' day Slaterkey,

Can you add some details to the issue you are having? How many miles do you have on the truck--is this a truck or SUV?
Is your clunk a rhythmic sound or do you only hear this once or twice?

You might want to begin by looking at the parts that wear the most: I would pull the rear driveshaft and examine the splines for wear, corrosion and other defects.
Then you could check all the universal joints for wear, binding or damage.

Also you might look at the undercarriage for things like loose or broken leaf spring attaching hardware, or even a broken bolt for the frame to body attachment points.
Don't start spending any money until you find something related to the sound and know its a defective part or not. It may be worth the money for letting a trusted mechanic put it on the lift and let you look at the undercarriage with him and check for loose suspension or driveline components.

Try this and let us know what you find...