[Gdaddypaul]

At 170K, the diff in my '07 SE, 4.0 six is "rumbling". Flushed lube, found some metal filings but nothing else. Noise seems a little less but still present. My questions are:
1.) should I repair or replace the rear?
2.) if replace, what other rears fit and are there other rears that could improve mpg in this "light duty" truck?
TIA, Paul

 

[whistler]

You will have to take it apart to determine if it is worth fixing.
No,changing rear ends will not improve gas mileage.Maybe if you go to taller gearing.

 

[shift_RUSH]

Have you checked your coolant color?
Do you know why I'm asking?

 

[whistler]

More than likely you have a C200K.
You also might have a M226.
Taller gearing than what?
We don't what the gearing is in your truck now.
This was suppose to go under your other post about differentials.

 

[Frontier4x]

Have you ruled out your wheel bearings, u joints, and transmission before deducing that the rumbling necessitates a rear diff replacement? Check these out first

 

[Gdaddypaul]

Yup. The noise is clearly coming from the rear's central hub. Maybe internal bearings (?)