I have a non-slip 3.73 rear end differential in my 2008 F350 6.4 diesel Super Duty, dually. I'd like to upgrade to a limited slip unit to give me better service for when I'm pulling my 40ft 5th wheel trailer. Presently the rear dually just spin on wet grass when under load. What information do I need when ordering an upgrade differential? Where do I find that information? Do you recommend another gear ratio for my application? Thanks in advance for your response(s).

 

If the one in my X or F350 geos bad, a Detroit TruTrac will go in its place. I have one in my chuvvy dually that came with an open diff. man what a difference. That thing is huge and works really well! Lots of people like them that have Excursions as well. I bought mine from Sadler Powertrain on the net. They can give you the info you need.

 

R U sure there is a difference between a "non slip" and a "limited slip". Sounds like the same thing to me. You may know more about this than I do but in case you don't look on the door plackard and see what it says. Should say something like "Axle 4L". That's what mine says for a 4.30 Limited Slip. I'm thinking that yours would have an L also.

As far as towing I always say that using the 373 to gain some fuel economy decreases the ability of the truck to tow some loads. Whether you will ever notice that or not is hard to say. I think it will most likely show up in higher tranny temps when climbing serious hills, like it the rockies or smokeys. My trailer is heavy, I'm at just under 26,000 on the scale and I'm very comfortable there isn't a paved road in the country I can't climb. But, my truck is a 2 wheel drive also, so I stay out of places that look like I can get stuck, And, like you I found that I was able to stick my truck in my back yard. The limited slip is indeed limited. The real embarassing thing was that my wife pulled it out driving my 92 acura. That is an absolute true story.

Maybe we both need more additive in the rear axle, I don't know. I'm coming up on 60,000 and I intend to have it changed out then, Hope this helps.

 

Yup, the door label shows the axle code as "37" which is supposed to be a non-slip differential. However I've been making the rounds of various Ford dealerships today, asking them to check their sources as to what is supposed to be in this truck per the VIN number. Some say non-slip while others say non-slip but can't belief that's the correct information considering the truck is a F350 diesel, full crew cab, 8ft box. I've got to find me a "Sherlock Holmes" type of mechanic who can get to the bottom of this. By the way, I just returned from Ashville/NC and the Blue Ridge Mountains. This was the 1st serious RV haul for the F350 and it worked like a horse, no wimpering, just kept slugging.

 

There should be a factory tag on one of the bolts on the rear pumpkin cover as well that i believe you can decifer the axle ratio/type.