Got one from our local dealer. I says my truck came with 3:55's. But I can't tell if I have a Limited Slip Diff. How can I tell?

 

Your build sheet will tell you. If it doesn't show anything about limited slip, then you probably got an open diff, aka 1 wheel drive, like me.
Is your truck 4x4 or 4x2? I'm not saying they don't exist but it doesn't seem like there are many 2 wheel drives with a factory LSD. Feel free to correct me if I'm wrong.

Nevermind, I see it now your's is 4x4, might wanna put that info in your sig.

 

Jack up the rear, put it in neutral, and spin one wheel by hand. If the opposite wheel spins in the SAME direction, you have a LSD. If it spins OPPOSITE than the one you are turning it's an open diff.

 

I don't know how accurate the spinning one wheel with your hand is. my Jeep had a LSD, but when I did the tire spin, the other tire spun opposite direction. But when I would play in the mud, or snow, or sand and spun the tires with more speed, they both would spin equally.

My build sheet for my 4x4 ram doesn't say that my truck has a LSD, but when I was power braking it to finish off my rear tires last week, both ended up spinning and I left two good spots of rubber in my dad's garage. (also the rear brakes needed to be replaced)

 

GM had the gov-lok differential. Needed a set amount of slippage before it would lock. So far as I know, GM was the only ones that used such a silly system. (it would POUND when it locked...... so a lot of those that turned themselves into grenades.....)

More often than not, the wheel-spinning trick on jackstands will tell the tale. You can leave rubber with both tires even with an open differential, if both tires have equal traction, and you apply enough power, both will break loose. Once loose, it's easy to keep them both spinning.

 

I've had both spin and mine is open.

 

Me too.

 

I think I have an open differential in my clutch cuz when I did a burnout the tires didn't spin but it made white smoke and smelled really strong! That's cool right guys??

 

Back to my question, lsd how to tell.

 

Jack up the rear, and spin the tires, or, pull the cover, and have a look, or, if it ain't on the build sheet, it didn't come from the factory with it......