Crown Vic - clunking in reverse

[panthermike]

Noticed this the past month or two on the Vic.
It is not when I engage into reverse, it is when the vehicle is actually in motion sounds like a clunking possibly almost like a binding. Does not do it in forward gears at all.

Any ideas on this? The only thing I can think of is possibly u-joints?

Otherwise the car goes down the road just fine at any speed, no unusual vibrations etc

 

[Warstud]

The only thing I can think of is possibly u-joints?

Yep

 

[MSCH]

might be getting excessive gear lash in the diff.

 

[Dinoburner]

Am in the u joint club. Likely the joint at the rear axle is going dry.

 

[panthermike]

Okay cool thank you all. U-joint is manageable! I'll look into it shortly here

 

[tasch72]

Check your driveshaft bolts. My Mustang GT had a clunk on decel. If you need a new set, they're about $5 for a set of 4 bolts at the dealership.

 

[Soft Cars]

Either U-joints or the differential. Don't forget that the driveshaft has to be put back in the exact same position in order to stay in balance.

 

[FordFETruck]

U joints, loose U joint flange bolts, excessive backlash in rear axle from wear as people already stated but I've seen dry slip yoke splines make noise shifting gears before as well as the stamped steel sun shell in the 4R70W and 4R75W's are known for the engagement tangs I guess you'd call them on the sun shell to wear and elongate and cause a clunking noise shifting to reverse mostly.