Just bought a used '04 SuperCrew Lariat and it doesnt have the original window sticker. Is there any easy way to tell if it has the limited slip option without actually trying it out in gravel/snow etc? Maybe some kind of code on the diff etc. I read the other forums regarding the LS and sounds like it doesnt work that great even if it is installed.

 

Crawl underneath and look for metal tag on rear axle cover. It will have several numbers on it but you are looking for the letter L mixed in with the numbers...example 3L73 would mean 3:73 gear ratio and L means its a limited slip.

 

Your axel code should be on a sticker on the driver's door. Do a search on the subject and others have posted what those codes mean.

 

If the axle code on the door is a letter and number, ex H9, it is limited slip. If 2 numbers, ex 19, it is an open rear.

 

Floor it, and peel out if you can, If you get 2 skid marks you have a LS if you get one, you have an open diff...

 

Another way is to jack up the back of the truck and put it in neutral and turn the wheel. If both wheels spin in the same direction you have LS and if the go opposite of each other its an open diff.

 

The stock trucks can do that???

Well Idk if his truck can do that but heres a sure fun way. Hold the brake all the way down and put the pedal to the metal and you'll have one nice burn out/smoke show. Oh yea, look at the marks. Same as above, 2 = LS, 1 = Open Diff

Edit: Btw, once i have both the brake and gas all the way down i have to let off on the brake a little bit to get the tires to start spinning so if you dont get any wheel spin with urs just let off the brakes a tad

 

Just do a power stand and see if both tires spin or not (put one foot on the brake while you give it gas until the tires spin). If you get 2 nice black marks, you've got the limited slip.

 

im with TX150. Floor it and see whatcha got. Unfortunately, I have an open rear diff. I think that should be illegal on a 4x4. Anybody know of any good LS diffs that can be installed easily and are good.

 

My dealer put mine in for $300. No problems yet.

 

Axle Codes

non-limited slip

27 – 3:31
19 – 3:55
26 – 3:73
25 – 4:10

limited slip

H9 – 3:55
B6 – 3:73
B5 – 4:10

 

Steve V. Is that 300 for the labor or labor and the LS DIFF. That sounds like a good deal. Too bad it wasnt stock in my vehicle.

 

Ive got a B6, thanks for the info.

 

300 for everything, but I had them do it when they put a new ring and pinion in the rear end, so it might have been less since they already had the rear end apart.

 

Now I'm bummed, I had assumed all FX4's had the 3.73LS, but my code says 3:55LS.

Was planning on moving to 305/70's but with 3.55 I may limit it to the 285's...