My 85 4runner just started making a clunk clunk sound when I go into reverse. It is louder when in reverse but when I put the clutch in it is much quieter but still there. Any ideas?

 

See if you can isolate where the noise is coming from and what frequency it is at, i.e. is it some multiple of wheel revs, or drive shaft revs, or engine revs. See if you can have someone drive it while you listen outside for the noise. Use 4L (front hubs unlocked) so you can slow things down.

 

The sound becomes more frequent as you increase speed in reverse. My buddy says it sounds like it's coming from the u-joint or the 3rd member, can't really tell.

 

Stop backing up.

 

drain (don't forget to refill) your rear diff oil and check for chunks of metal