How often to change rear diff fluid and spark plugs?

How often should I change rear diff fluid and spark plugs? I am assuming 30k miles on the rear diff fluid, is that correct? Spark plugs I haven't found any info on.

I want to keep up on this, since I run my truck hard, I tow my 5x8 enclosed trailed weighing roughly 2500lbs loaded 90% of the time I drive my truck.

 

15k for fluids & 30k for plugs. You'll get mixed opinions though

 

Me 3.

 

I went 120k on my plugs

 

On my 2007 I done both at 40 k, the diff fluid was jet black coming out. I would do now at 15k on my 2011. The plugs I changed at 40k and they really wern't too bad, I will do these at 30K this time.

 

Changing the plugs at 30k is a waste of money.

 

Any input from those who tow a lot?

 

I do both at 30K intervals.

 

Plugs are always 30k. Any longer and the gaps will be crap (I know).

I waited about 40k my last rear change and the oil looked like shit and the drain plug was complete glazed over with 1/4" of metal shavings.

Now I know better so I would NOT run the rear more then 15k. It's so easy and cheap to do there is no reason to wait any longer. It takes 5 minutes to do....

 

What oil do you use?

 

Yeah yeah well what I should have said is I'm lazy and it's not happening till next oil change. Anyway oil suggestion for sport with the lsd?