Rear lock differential??

[sduncan20x]

I have a 2wd 4.6.

I want to be able to pull heavy ass loads with it.

but i was also wondering if it would help with the off roading to?

 

[KWT2000]

being 2wd you more than likly have a limited slip diff already

 

[tonydiv]

You may need to define 'heavy ass loads' for us.

 

[sduncan20x]

like a trailor of horses, cows.
A pontoon boat.

 

[nvycrmn]

a locker in the rear would help for offroading but you dont want that engaged while towing. you will tear through those gears. if you need more towing power, look into tranny/engine upgrades or regear. besides, a selectable locker is gonna run ya about 1k plus installation.