Clunk noise when driving in reverse with steering at full lock

[ovlov760]

My car is a '98 V70 AWD. The AWD system is still functional.

After sitting most of the winter the car has developed a new noise. When I back out of my driveway and turn the steering all the way to full lock I hear a thunk/clunk that continues as long as the car keeps moving. It seems worse if the steering wheel is cranked all the way to the right.

The noise does not occur when the car is stationary or moving forward at full lock. It just occurs when I'm moving in reverse at full lock. My impression is the sound is moving more from the right side of the car.

I had the front passenger side wheel off but didn't find anything clearly loose. The boots on the CV are intact and there are no signs of grease being slung.  The power steering fluid level is good.

The car had the rear calipers replaced before going to sleep for the winter. In the prior year all four tires were replaced. In the last 3-4 years the front strut assemblies were replaced the Sachs units, rear Boge shocks were replaced, all the sway bar end links were replaced. It had an alignment at the dealer and still holds it.

I greased the steering stops with generic grease but it made no difference.

I did figure out today that the shop that replaced both calipers over torqued the lug nuts. I can't really find anything else that's off.

The car drives, stops, and turns fine. There's no strange noises when driving over the terrible IL roads. No clunks or creaking noises. I have no clue what's up with it. Any ideas? Thanks.

[Boxman]

Usually clunking at full lock is caused by CV joints. Boots and grease can look good, the joints can still be worn internally. This usually makes a clunking noise.

[BEJinFBK]

Time to inspect the front CV of the rear driveshaft.

It’s just inches from the catalytic converter and the

heat tends to bake the boot of that CV joint.

It’s probably gone and the joint is failing.

 

Good news - It’s not a huge deal to replace. 😎

[apeacock]

Weird for sure. I had an awd noise when going forward and backwards (just one time each way) that turned out to be the bushing at the front of the torque tube / viscous coupler. It would tension either down and bonk or up and bonk the cars floor. Was not continuous but worth a look. I always though CV joints made a click click click as they rotated when dead / dyeing. 

[B_Dub]

My car did the same thing years ago, pronounced clunk when in reverse and turning in one direction. Ended up being the Viscous Coupler.

Rear propeller (drive) shaft center support bearing failure can also cause similar noise, but the fact that it only happens in reverse and when turning leads me to suspect faulty Viscous Coupler (torque tube).

[apeacock]

On 4/13/2021 at 6:27 PM, B_Dub said:

My car did the same thing years ago, pronounced clunk when in reverse and turning in one direction. Ended up being the Viscous Coupler.

Rear propeller (drive) shaft center support bearing failure can also cause similar noise, but the fact that it only happens in reverse and when turning leads me to suspect faulty Viscous Coupler (torque tube).

I forgot about how much the drive train torques the prop shaft around that would do it in both directions and especially when turning.