I test drove the 3.55 with the e-locking rear end and wasn't very impressed at all. I was asking myself what the point of this was and am writing this to see if anybody can answer it for me because I am sure Ford does have a reason for it. Here's my view. If you put it in lock mode it only works up to about 20 mph then goes back to regular one wheel drive. The problem I have is say when it is raining out and you are going 30 mph and you punch it, with these crazy powerful diesels you are definitely going to spin the tires in which you lose control with the e-locker. If you get just the regular limited slip differential when going 30 mph and punching it the tire will slip momentarily until the axle locks up automatically helping to gain traction. Can someone please tell me the big advantage to get the e-locking rear end? When I plow I'm in 4x4 and was thinking that you could maybe just plow in 2 wheel drive with the rear end locked but that's all I can see this being good for. Hopefully I will be signing paper work on my truck tomorrow and would like some feedback.