Knocking at My Back Door?!

[4epBeu]

Hi guys,
I did the seasonal service - engine, transmission, differential, brake lines, clutch lines, servo, sway bar links, brakes...nice!
But i hear a knocking sound from differential!
is there an allowable clearance that would justify this or is anything short of absolute silence considered a problem?

Dodge Viper SRT10 2003 28k miles

 

[GTS Dean]

Could be a CV joint going bad. The diffs are also known to be problematic. Drain the fluid and check for metal.

 

[Old School]

Did the knocking sound start when you changed the gear oil? If so, could be lack of friction modifier.

 

[Steve M]

Definitely time to start investigating.

Answering Old School's question is a good start. It would help to have more info about when you are hearing the knocking sound.

In general, there shouldn't be any noise coming from the rear diff. You may experience some excessive lash in the drivetrain when the car is cold (some people refer to it as "the clunk"), but that should go away after it warms up. The Gen 3 diff, specifically the limited slip carrier (Hydra-Lok), is a known weak point. The spider gears are typically what breaks.

If there's any gear whine or clunking going around turns, that's not normal. I've rebuilt two of my own differentials (I have a spare to eliminate down time with the car), and both have been dead silent after the rebuild. You don't have to live with a noisy diff, but it does take time to set it up right.

The guy that inspired me to rebuild my own diff shared his experience here: https://www.viperclub.org/vca/threads/my-diy-differential-gear-change.659129/

The pics are gone and he no longer owns a Viper, but he can still email them to you if you reach out to him. FWIW, he found broken spider gears when he tore his down.

If you want to see how these differentials are built, I've put plenty of pics in this thread: https://www.viperclub.org/vca/threads/viper-dana-super-44-rebuild-how-to-gen-3-4-5-2003-2017.678645/

I'm working on some updates to that thread now.

 

[4epBeu]

I've changed the fluid with Mopar + modifier, the old one was clean of metal. There are no leaks or something disturbing.
Rotating the wheel when the car was up on stand is how I found this...slack.
How to distinguish if the problem is in the CV joint or inside the differential?

 

[GTS Dean]

Have a friend rock the wheels F/R with no load. Feel around the inner and outer half-shaft connections for slack associated with the knock. Expect some gear lash in the diff itself and filter that from the shafts. This would also be a great time to check toe links by grabbing at 9 and 3, then feeling for play in the tie rod boot.

 

[4epBeu]

There is no slack in outer part of the axle!