This is how the story starts. My friend called me and said he was hearing a clicking noise from the front of car sometimes on acceleration. I told him it might be the CV joints but it was weird that they were making the clicking noise going in a straight line vs turning. I told him to bring it in over the weekend and we could swap out known good ones to see if it fixed the problem. Yesterday he called me and said that he was accelerating from a stop and he heard a loud pop and then a subsequent thunk-thunk. I thought the cv joint might have broken and he was hearing the shaft bounce around. The car is now in my shop all four wheels up in the air. The symptoms are: LOUD thunk about every 1/2 rotation of front. Feels like something binding up. I unhooked the front cv joints ( which looked/and felt ok) and put the car in drive/reverse and the noise is still there. My gut reaction is a bad front diff. I am going to drain gear oil to see if there are metal shavings etc. Anyone seen this? Are these front diffs known for failure? Thanks, Craig

it's not common, but it can happen.

 

I'm in the process of rebuilding the front diff on an 03 H6 Outback right now.

 

for a 4cyl model you may find it more economical to source a used trans.

 

this rebuild cost $700 plus in seals, bearings, and ring/pinion set (ring/pinion is $350 alone)

Not at all common - I wouldn't even consider rebuilding it with used transmissions being likely cheaper than just the ring/pinion set.

 

GD

Broken tooth on the ring gear maybe. Every half rotation would make it two teeth though. One on either side of the ring gear. It happens.