Two 4Runners, a 2005 and a 2007, both with V6 engines. Backing up a short steep muddy hill (to unload the vehicles), I put it in 4WDLo and diff engage diff lock. The 07 never has any issue with tires slipping. The 05 would slip/slide and could not get up the hill (and it has much more aggressive tire tread).

The 05 appeared to be engaging the diff lock (light was solid when engaged in neutral), and it disengaged the VSC, but it was definitely not acting like the diff lock was working.

I since then did some testing in the driveway to see if the 05 was acting normally. I started vehicle, put in neutral, engaged 4wd and once engaged, I tried putting in gear followed by trying to engage diff lock. It should not engage in gear and it did not. Then I tried slipping into neutral and it engaged and VSC light came on as well (as expected).

Bottom line, is it seems like it is engaging, but it sure does not give the traction of locked diff.

Any ideas?

Pat