Vehicle capacity weight reduced with locking rear differential?

On page 462 of the owner's manual, it indicates that the load capacity of the 4Runner is reduced by 330 lbs. if it has a locking rear differential (1165 vs. 835 lbs.). I'm trying to figure out why this is so. Does the locking mechanism add 330 lbs. to the vehicle weight? Is the body-to-frame clearance reduced with a locker? Does the locker somehow compromise the strength of the drive train? Would the reduced capacity only come into play if the differential is locked?

I'd appreciate any knowledge someone may have in this regard...thanks.

 

Yes, it adds weight which reduces the load capacity. Notice that the 4WD probably has less capacity than the 2 wheel drive, due to the weight of the equipment.

I drove on a mountain trail yesterday that you could not do without a locking differential. Miller Run, starting in Frazier Park, CA has a lot of steep grades with loose dirt and big embedded rocky "hurdles" to climb over. I needed every bit of traction I could get to do it. I did the entire trail without spinning my tires much. I climbed over some tough terrain by going slow and steady with the diff locked.

One of the guys had a Nissan Xterra that did not do so well. He said he had 4 wheel drive but I thought he had all wheel drive or a limited slip transfer case because when he got stuck either the front axle or the back axle would spin while the other axle didn't even turn. I think it was only driving one wheel at a time. He had no lift, no locking diff, no rock rails and his spare strapped down to his roof rack.I don't know what year it was. It looked like it was 12 to 15 years old. He kept talking about installing a lift. I told him he needed rock rails first, then a locking diff. But what he really needed was to start with a better vehicle.

Without a locking diff, anywhere you drive that causes your vehicle to come to a stop while balanced on two opposite wheels (ie, balanced on the left front and right rear) will bring your vehicle to a stand-still that you can't get off of. One of the wheels on both axles will be off the ground enough to loose traction and the free wheel on both axles will spin. The only way off of that spot is to pull the vehicle off or jack one of the free wheels and place some rocks or boards under it. We had to do that with the Nissan Xterra a couple of times yesterday. That's the shortcoming of the SR5 compared to the Off Road T4R. No locking diff.