Clunk while accelerating from coasting
 

Our 2004 Navigator has developed a pronounced clunk, which is reproducable if you're driving at highway speeds and let off the gas and coast for 5-10 seconds. Then when I step on it, I feel a clunk, almost as if gears were engaging. I'm pretty sure it's the rear, this happens in 2WD (haven't tried it in 4WD mode).

If I accelerate gently, it doesn't make the sound. I'm somewhat mechanical and for those who are familiar with Volvo Outdrives, it's a similar clunking noise when they engage into gear.

I've worked on Volvo's for years, but I'm just not familiar with Ford products and SUV's.

I'm thinking either suspension or in the differential. Any thoughts or ideas ? The car has 98k miles on it, and has generally been taken care of.

Thanks !

Start by checking the u-joints in the driveshaft. They you could check the play in the ring and pinion. Check the transmission mount, and any mounts in the rear diff cradle.

This may be tricky to isolate because it requires a bit of engine torque to make it happen. Whatever is clunking may not be so loose yet that you can see it or feel it without driving.

Had a similar sounding problem last year in my 99 Expy - (https://www.ford-trucks.com/forums/8...eleration.html )

After checking u-joints and driveshaft as suggested here, my issue turned out to be the front transfer case. Replaced with a reman'd one and everything has been silent since :-D . Worth considering....

HELP PLZ
 

Did you ever figure out the problem causing this issue? I've changed the rear diff, rear axles, engine mounts, transmission mount, rear differential arm mount, u-joints...everything. I can't afford to keep guessing.

cddulin did you ever figure this out? I am in the same boat.