Weird whine and clunk in C4 when decelerating

[Chief Master Sergeant]

Trying to help a friend diagnose this strange noise. Only happens with transmission in drive and when the vehicle is almost at a complete stop. Steering linkage and ball joints are tight. Ujoints have no play. Brakes have been ruled out, as the sound does not occur when we put it in neutral and stop. I think it’s transmission related, but a local shop is telling him it’s not. Anyone have thoughts on what could be causing this?


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[Oldtimer]

Transfercase?
What does it sound like in low range?

 

[Chief Master Sergeant]

Transfercase?
What does it sound like in low range?

He just drove it in 4 low. Same issue


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[joebronco73]

Has he greased all the u-joints? Grease them until it oozes out.

 

[spap]

Loose u bolts ?

 

[Broncobowsher]

Rear axle pinion bearings.

 

[Chief Master Sergeant]

Has he greased all the u-joints? Grease them until it oozes out.

Done


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[Chief Master Sergeant]

Loose u bolts ?

Nope. I checked that


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[Chief Master Sergeant]

Rear axle pinion bearings.

No, we pulled each drive shaft and drove it without each individually. Same issue


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