My 87 Bronco has recently developed a popping/clicking sound while under load. If I rev the engine in park or neutral there isn't any noise. Also when rolling if I put the truck in neutral the noise stops immediately. I have done as much research as I can find and found two possible causes. One is the 4wd hubs partially engaging on their own. I bought the truck used and have never used the 4wd as the switch to engage is gone. Also the sound seems to be coming from the rear. The second is a cracked tooth on the rear diff. Recently the truck was used by my son to pull a trailer with a car on it a few times. I've gotten under there and checked the drive shaft and u-joints and all seems to be ok. So basically I'm short on cash so the work will need to be done by myself and my son. Also I'm short on rear end knowledge, my only experience was swapping in a junker rear axle on my F-150. Any advice on how to check the diff as well as any alternative suggestions on some other possible culprit will be much appreciated. Thanks.

-Chris

 

One diagnosis step that I can think of is to jack up the truck and run it while looking for where the noise is coming from.
this has to be done carefully, obviously.
Pick a level spot and jack up and support all 4 wheels then run the drivetrain and observe and listen for the popping noise.
If there is no noise because of no load, then I would think that it's differential related.
Rear axle swap is the equivalent to F-150.

 

Actually sounds like u-joint related.