I have a 2wd 4runner and see at different places that a locker can be put in the rear. What cost and difficultly is involved in this. What would be the big benefit. Would it involve tearing the rear axle down?
I might suggest checking out the Tacoma forums. PreRunner Tacoma’s are 2wd trucks fitted with the 4wd suspension package and a factory rear locker. They’re pretty popular because, per the argument, they have the same ground clearance as a 4wd, are less expensive, have cheaper insurance, and get you out of trouble if you find yourself over your head off road. The various pros and cons are well debated over there.
Had a 16 TRD OR Tacoma 2wd with a locker. That locker got me out of a pickle or two. But I traded for something with 4x4 when I got hooked into wheeling. It was a fantastic truck honestly, but there is no substitution for 4x4.
For example with the tacoma I put myself in a situation. A rocky/shale accent with a decent grade to it. Only one way out and that was up. If I had 4wd i could have walked up it (especially with all the traction options I have in my TRD OR T4R) with minimal stress on my driveline. Instead I had my passenger get out (weight reduction) to go full send with the locker engauged and bounced my way up this rocky face. It was super fun and looked ****ing cool (apparently), but it's situations where you take the truck to the limits of what it's capable of that you break shit.
In short if you think your going to need that locker you might consider just getting a truck that's up to the job.