How can I tell if I have a limited slip in my '01 F250 4WD? I need to know if I need the additive for the gear oil. Thanks guys.

 

Look at the sticker inside the driver door jamb where it says axle if it's a letter and # then it's limited slip

 

check the tag on the rear axle cover...if limited slip..it will usually have the gear ratio as 4L10 instead of 4.10....one other way is if both rear wheel are off the ground and in neutral, you manually rotate the tires and they both turn in same direction it is limited slip...

 

If those two methods do not tell you, go to https://www.etis.ford.com/ , click on the VEHICLE tab and enter your VIN.

 

this would be the sure way to tell. because someone could have done a swap in the past. unless of course you are the original owner.

 

"click on the VEHICLE tab and enter your VIN."

Correct, BUT you have to click on the "minor items" to check for LSD

 

That etis site worked great. I do have a limited slip. Thanks guys.