Clunk Sound(Not U Joints)

[Rusted1]

I replaced 3 ujoints in the main drive shaft today and still have a clunk when I shift into reverse or into drive. I have a C4 trans. Could this be a third member problem or a trans problem ?:? What would I look for or have to replace in the third member if this is the problem ?:?

 

[GRIZZLY]

May also be your slip yoke on the drive shaft........

 

[JTCamp]

I agree on the slip joint. Grease that baby up and see if it makes a difference.

John

 

[75MIKE]

Chock the wheels and put the tranny in neutral so the driveline has no tension on it. Get under the rig and push and pull the rear driveline and see if there's any lateral movement in it. Then one hand on the driveline other on the slip yoke and turn opposite directions and see if there's play in that.If so , might be time for a new slip yoke and a re-spline. You'd be surprised how much that will tighten things up.

 

[CrazyHorse70]

Have you looked at the bushings in your leaf springs.
Automatics tend to exibit spring warp more than standard trans., had a friend with a '73 that had that problem. Just a thought.

 

[GRIZZLY]

Also, a Detroit locker will have a slight clunk as it engages.

 

[Rusted1]

[quote author=75MIKE link=board=5;threadid=14779;start=0#111608 date=1046581294]
Chock the wheels and put the tranny in neutral so the driveline has no tension on it. Get under the rig and push and pull the rear driveline and see if there's any lateral movement in it. Then one hand on the driveline other on the slip yoke and turn opposite directions and see if there's play in that.If so , might be time for a new slip yoke and a re-spline. You'd be surprised how much that will tighten things up.
[/quote]

75 Mike, I did the above as you mentioned and the slip yoke seemed to be tight. However as I attempted to rotate the drive shaft back and forth, I heard a noise coming from the third member area near the flange. Should there be any play in this area ?

 

[75MIKE]

Yes, There will be a little bit of play in that. If the ring and pinion are worn , depending on the age, the play will increase. This of course adds even more "clunk" to the rear-end. How's your idle speed ? If it's too high it will also exaggerate the clunk when you go from park to drive or reverse.In my travels I have not found any Broncos that were "clunkless", unless it was right after the rear-end had just been re-done and backlash set.