twinscroll

I noticed a small whine from the front diff a few weeks back and found it to be coming from the left front diff side bearing after a little inspection, time for a rebuild. I know i found a thread of someone attempting to rebuild the unit but only did the side bearings but since i decided to do the pinion shaft bearings as well i figured id post some pics of the rebuild for fun. Ended up replacing both side bearings, pinion shaft bearings and outer races, tail shaft bearings, pinion shaft nut, both side seals, some case o-ring seals, viscous clutch snap ring and washer, and spacing washers for setting pinion ring gear backlash. enjoy!

halo777

Nice work!

DaveCarrera4

Outstanding! I replaced one side bearing, that was easy. You really dug into it.

Dennis C

Strong work. I had mine totally rebuilt last year.

KrazyK

Awesome pics and job. If you dont mind, what was the mileage? Was there a maintenance issue? Personally, I dont follow the longe fluid change interval recommended so I changed mine much sooner. With proper maintenance, the front dif should have lasted well over 100K before a rebuild. Anything unusual with this one?

Zookie

wow intresting! i only get a Whine at a Certain speed with my Summer on, but not with the WInters.

mcbit

I very occasionally get a bit of howl slowing down, but only on certain road surfaces. Might be harmonics?

Dennis C

Mine started to whine at highway speeds before it failed... it was very subtle.

In the final stages of failure, there were two additional symptoms:

1. Leaking. It wasn't significant, but there were a few spots on the garage floor.
2. Noise. It sounded like a slipping belt coming from the front of the car, most noticeable when decelerating.

A rebuild is a much, much cheaper option than a replacement. A dealer will typically replace the entire unit rather than rebuild it. The part alone is close to $7,000.

wwest

Any indication of failure whatsoever and mine goes into the metal recycle bin.

Useless.

twinscroll

thanks everyone. the diff had 70k on it, there was no maintenance issue i changed my fluid prematurely (30k) as well. nothing unusual found inside. i just rebuilt my friends front diff as well his side bearing completely failed, luckily leaving no damage to anything since the bearing cage blew apart. his front diff had only 60k on it.

twinscroll

i would have done that but as a daily driver in WA and winter coming up i figured it to be somewhat useful to rebuild. Let me know if it starts to fail more than happy to help if you choose to rebuild it.

Dennis C

Interestingly the AWD system on the 996 wasn't designed for additional traction in slippery conditions or winter driving. It was designed for improved performance on dry pavement. Your best bet for winter traction is proper winter tires, not the AWD system. The viscous coupling only drives the front wheels if there is a speed differential between the front and rear wheels, such as when the rear wheels are slipping. The PSM system prevents the rear wheels from slipping. Therefore, the front wheels don't do much in winter conditions. On the track or when cornering on dry pavement, the speed differential between the front and rear wheels allows the front wheels to engage and help to pull the car through and out of the corner more aggressively than a RWD car.

BAD.TAG

The great thing is that you can remove the AWD components for repair and still drive the car =)

wwest

Plus wintertime COLD conditions make the VC even less functional.

KrazyK

Well thats just fing great, bro. If we didnt have enough 996 bs problems, now us C4S owners can add this to the list of failures to fear.