I just recently purchased a very clean 86 4WD Bronco II with a 193,000 miles. The auto tranny was recently rebuilt by previous owner and I had to rebuild the entire front end including brakes,shocks all the way around and grease the single carden joints in the rear driveshaft. I got a strange noise that I can't pinpoint and it doesn't do it everytime. When slowing down under load I hear a popping noise from time to time;sounds like it's coming from the center but you know how noises can be misleading. If I gradually slow down you want hear it but if you are moving on the interstate and hit a exit ramp and come to a stop fast you will hear it. Sometimes you will hear it on turning in town if the tranny downshifts then upshifts again.If I slow down fast and put tranny in neutral and come to a stop everything sounds fine but in gear the popping sound may happen. The ujoints seem fine and I've checked all bushings from front to rear and they seem OK. While the vehicle is parked and the engine off you can push and pull it from the bumper and it will roll back and forth about 6" and you can also turn the driveshaft alittle up and down but being so road old I can understand the slop in everything. Anyone dealt with this before I start replacing parts; I hate to throw money at it hoping to correct a problem.

 

What is the condition of your exhaust system? Could you be hearing a light backfiring sound?

 

Weird sounds are hard to describe unless you experience them-the exhaust is OK. My noise is more a clunk and pop. When I roll the Bronco back and forth in the driveway (in park) you can see the diff housing move up and down with the rotation of the driveshaft; it's not slight but very noticeable but as before - while driving if I put it up in neutral before coming to a stop you hear nothing;it's only when the tranny down shifts back to one on a stop that you hear it and not all of the time. This weekend I'll install new rear joints and sway bar bushings (rear) and see where I'm at.

 

check your ball joints.

 

Find a drive shaft at the bone yard that has a single u-joint at each end and get rid of that cardan joint type shaft. Bolts right in and they are very easily repaired when needed and work and last just as long. I've done that to every B2 we've had once the cardan style started to make noise.

If you can't find one and would really like one let me know, I think I have a extra one out back. You shouldn't have much trouble finding one near you though.

 

The popping sound from what you describe is most likely radius arm bushings. Bad ones (they might not be installed correctly if new poly) cause the sounds whenever the nose is pitched forward. Usually happens when braking.

You can always crank down on the nut a bit to see if it changes anything.