How to tell if your car or truck has a limited slip differential

This video shows you how to tell if your rear wheel drive car or truck has a limited slip differential, and also what gears it has. It is quick and all you do is read the tab on the differential pumpkin, or lift the rear and spin the tires... While moving one tire by hand, If the tires move in the same direction (or one doesnt move), it means that it is most likely a limited slip (posi traction) rear end. A limited slip rear uses a special additive to the gear oil when you do a gear-oil change, and it is necessary or damage could occur. An open differential (like the one in the video) does not use the special additive and the tires spin in opposite directions when one tire is spun.

**If the video was helpful, remember to give it a "thumbs up" and consider subscribing. New videos every Thursday**

Disclaimer:
Due to factors beyond the control of ChrisFix, I cannot guarantee against improper use or unauthorized modifications of this information. ChrisFix assumes no liability for property damage or injury incurred as a result of any of the information contained in this video. Use this information at your own risk. ChrisFix recommends safe practices when working on vehicles and or with tools seen or implied in this video. Due to factors beyond the control of ChrisFix, no information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. Any injury, damage, or loss that may result from improper use of these tools, equipment, or from the information contained in this video is the sole responsibility of the user and not ChrisFix.

[marshalllhiepler]

The video instructs us to jack the vehicle up, so that the wheels are off of the ground, and to place the vehicle transmission in "Neutral".
As a professional mechanic, I just wanted to note that the transmission does not need to be in Neutral. An automatic transmission can be left in "Park", or a manual trans can be left "in gear". If the vehicle has an "Open Differential", the wheels will spin in opposite directions. Some locking units act like open diffs, until the engine applies torque.

[buddyro]

4-10 doesn’t mean “4 to 10” for your gear ratio, it means your ratio is 4.10 to 1. (Your driveshaft will turn 4.10 times for every revolution of a wheel).

[kukovich]

3 weeks, 2 rear ended and 8 hours into finishing up installing the second, your video came in hand!. Thank you for posting this info.

[kal]

So I just learned the hard couldnt read the tags....so jacked up my jeep CJ5 with Dana 44....spun the wheels....tires went opposite directions. I ordered an auto locker, pulled the diff cover and lo an behld....I have a Trac Lok with worn clutches

If the clutch pads are no good....a Trac Lokwill behave like its open.

If you drive a at the tag or open the diff BEFORE you buy any parts....the old spin trick isnt reliable every time

[Chris-sgby]

I have everything I need to change some rear axle shafts and change the diff fluid and I kept wondering whether or not is it a slip or not.
Thank God for this video, thank you Chris!

[chrisfix]

One of the best ways is to look at the tag because so many companies make different differentials and they react differently. This is specifically for Fords and Mazda but does work for other manufactures. It is only a reference tho. Check the tag on the differential to be sure!

[Chrislav]

Essentially. A LSD will spin one axle a small amount before locking them both into a posi style axle(That's the "limited" in limited slip). It makes for much better cornering. With a Posi you see a considerable amount of "wheel hop" during turns.

I thought they were the same thing too until just recently when a Ford guy called me out when I said my mustang had posi lol.

[richy]

Chris Fix this was VERY helpful! Your a life saver

[Methodical]

Great visual. If I did not know what I have for some reason I would install fluids with friction modifier that way I am ok either way.

[gilbertsalvaleon]

Ok Chrisfix now I know how to determine a limited slip differential and non limited slip differential, very nice video tutorial Chrisfix, ur video tutorial helps me a lot because I am a automotive student, for me ur a very good mechanic instructor.I wish I will be ur mechanic assistant someday.😀

[tartredarrow]

I'm jealous of your differential ratio. I have the 3.73. I want the 4.10 for better acceleration. I have the 4.0L SOHC, so I could be having a lot more fun!

[aeromaxout]

@ChrisFix Boy have you grown your channel since this one came out. A mix of shot quality and your signature professional yet excited narrations have kept me a well pleased subscriber.
But it is interesting to see just how far you have come in the last eight three quarter years. Not that this was bad; about average for the market actually; but that you have risen above what is expected on YT and have built a sturdy brand, of which I recommend to anyone I know who is working on a vehicle for any reason.

[chrisfix]

It is def not a method to rely on but if you know a little about your car, you can use it to figure out what kind of diff you have. Also, thanks for the gear info. I dont know if you saw the annotations, but I corrected myself with that info. I misspoke when making the video.

[harvestblades]

So in my experience a limited slip differential (LSD), posi, or various lunchbox lockers require a certain amount of rotational speed before the clutch packs engage. You can lift it and spin it as you are you just need to do it with some power. It is dependent onnthe type of clutch pack whether you need a friction modifier. You may also have a limited slip diff, but either due to not having the friction modifier added or the clutch packs which are washers coated in a friction material like breaks are worn down to the point they will not lock the rear reliably, & this is a very common issue. Good try, but there is a bit more to how these work & how we can check for them.

[Imustfly]

You must have a little more wheel speed before the spider/side gear interface will create enough force to close the clutch packs. Until then, it will APPEAR as if it's an open diff.

[florianzauner]

Hi Chris, why I'm not wondering it's you answering my question again, like so many times. Thanks for helping me out again:-) Greetings from Germany.

[DonTruman]

From watching Engineering Explain's video on limited slip, there needs to be a certain amount of rotational speed before some cams swing out to engage the limited slip. Therefore, this test wouldn't identify it.

[jailanrayvon]

What a transformation your videos have went through

[seahawksforever]

I have two 3 ton jacks. I just lifted the rear wheels both up and it spins in the opposite direction so it's not an LSD like you stated. Thanks!

[captmack]

amazing how in all the comments people dont know the terminology. "Limited Slip" is the generic term. GM calls limited slip "Positraction"(posi)  Chrysler calls it "Sure-Grip"  Ford is "Trac-Lok" all are limited slip. Auburn makes the limited slip called the "Detroit Locker". As opposed to open differential or the always locked up, "Spool".  and there are many other brand names for LS from all the others, Porsche, etc, and ways that they work too. I suggest y'all read the wikipedia page, just google limited slip.