Should center differential be replaced if only bearings bad?

[walkerhollis]

I just had my 2007 Outback with manual transmission, 107K repaired.  I took it in because of a whining noise that typically correlates with central differential bearings. No other symptoms. The Subaru dealership replaced the bearings, the central differential, and the gears.

 

Upon picking the vehicle up, I asked to inspect the old parts with the mechanic.  The only visible damage/wear was to the bearings as noted by the mechanic. The gears looked good.  The differential had some signs of heat coloration.  The dealership said they replaced all the above parts because of the mileage and to prevent a return visit. The mechanic pointed out the heat marks, and stated that often after a repair of just the bearings, he finds other components may not match up(gears). The end result being I would have it back soon for another repair. While I partially agree with his logic, I have a hard time replacing parts with no damage.

 

Should I be appreciative of this preventive maintenance, or was I taken for a ride?!

 

Thanks for you insight,

 

Townsend.

[idosubaru]

what you're describing sounds like a front differential but you said "center" differential and both are encased within the transmission. are you sure it wasn't a front differential or front ring and pinion gear set?

 

almost positive people have replaced the bearings alone without issue, but it's a rare repair due to the complexity of it.  and that may also lend to cautious technicians.

 

can you post the part numbers replaced?  probably bearings and ring and pinion set ("gears").  that would have been like a $2,000 job.

 

center diff replacement would have been like $500...plus whatever extras i can't guess.

 

if you're positive it was the center differential....we'll need more info since that sounds odd.  there are quite a few "gears" and "bearings" in a manual transmission, can you post the part numbers since none are typical replacements in coordination with a center differential?

[Fairtax4me]

Heat damage to the center differential definitely warrants replacing the unit.

The transfer gears maybe didnt NEED to be replaced but with the proximity to a failed bearing there is a good chance of accelerated wear on the gear teeth, and the transfer shaft bearings could fail soon after as well.

[nipper]

Yes we need come clarification on what was replaced. The "center differential" is usually replaced for torque bind. I can't even think of the last time someone replaced those bearings if ever. It also is a silent death. There may be a clunk, but no whine.

 

Now, a normal diff (front or rear) will whine as it slowly dies. The volume of the whine will increase with speed. Now If the bearings are bad, it will cause the drive pinon gear to go out of alignment. In a Diff the clearances and contact patches of the gear are critical. 

 

Now this could have been a problem long before you heard it to become aware of it. Without seeing the parts in question myself, I will side with the mechanic on this one, as the last thing he wants is an angry customer to have a double labor charge to replace a diff.

 

Here is a pic of the inside of the diff

 

As you can see alighnment of the pinion gear is very important.