2001 6 speed dana 80 rear end. i peeled some tire and only one side grabbed then the other side started grabbing. i looked up how to tell what diff you have on google. i jacked the truck up and rotated one tire. the other started spinning the opposite way a little. but when i put the truck in gear when jacked up they both spin the same way, when giving it a little gas one tire spin a little faster then the other but the other side would catch up. i dont understand this at all could something be worn out? cause the tire would start grabbing..

 

One word YES

 

yes to?

 

You have a Dana 80 limited slip rear end. The clutch packs in the diff are probably worn down to a point where they aren't providing enough friction to make the other wheel grab up when the opposite starts to spin enough to wind it up.

Mine still gets a little torque to the opposite wheel after 150K miles...not bad.

 

@sixslug you think i do? and is that something i can fix or?? i been researching like crazy on the packages that came with those trucks. for LSD you need package 27G/28B/2GG/2CG/2BG/ or DMF. my truck is a slt 6 speed there are only 2 packages that came with a 6 speed. ST or SLT. SLT 6 speed cummins package code is 2BG (can have LSD) for a ST 6 speed the package code is 2BA and its not shown that it could have been ordered with LSD. so im guessing cause my trucks a SLT 6 speed it has it. but just to make sure imma call the dealer and ask for a build sheet and see just for myself.

 

i research to much.. sorry. never can learn enough! but anyways heres a video of me trying to spin my tires in my truck. what ya think? you can see the driver side trying to bite. https://www.youtube.com/watch?v=nK-B...ature=youtu.be

 

What does the tag under the hood say?

Or, you can input your VIN here and it will tell what your truck was originally equipped with.

VIN decoder is the best online tool to check vin number | VinDecoderz.com

 

thats the vin decoder i use. and my glove box sticker is so faded i cant tell. where under the hood would it tell me? did you see the video i posted? see how it would grab somewhat

 

Your rears sound like an open rear, not a "Limited Slip" you may be able to have your vin decoded, unless you are the original owner there is no guarantee it's stock, best way is to pull the cover.

Mine has 255k, and the clutch pack is still very tight, grumbles in tight corners.

 

The video really doesn't help except to prove you don't currently have a working Limited Slip. The question is do you have an open rear, or a worn out Limited that needs refreshed.

Even Opens will transfer somewhat, one of the old time tricks with open rears was to slightly push on the brake pedal to lightly drag the rear brakes and that would help transfer the torque across.

I am confused though, did the VIN decoder say you have a limited or not?

 

Pull the cover, always a chance it got swapped out.

 

If you jack up the truck and spin one tire by hand and the other tire spins the OTHER way, you have a open rear end.

 

This is "supposed" to be the way a LS works when checking by hand.....

Jack up the entire axle so both tires are off the ground.
Spin one tire by hand and if the other side moves obviously AND freely in the opposite direction then its an open carrier. There will be no denying its movement either as everything you do it will want to move exactly in the opposite direction.

But.....if when you spin one tire and the other tire kind moves lazy and not sure what direction its going to take, as it will move one way or the other dependent on what you do.....then you simply have a LS carrier thats probably set loose or the clutches are worn down.

Now its important to understand how a limited slip carrier works because most people are misunderstood by people telling them that its merely clutches in the carrier which hold the axles from spinning separately. Well yes thats true.....but no, thats far from how they work. LS carriers have whats called static pressure which dictates how much initial pressure the clutches have against them with zero torque applied. A carrier with high static pressure will NOT allow the other tire to spin in the opposite direction by hand because there's too much initial clutch pressure forcing both axles to move in the same direction as you spin the one tire by hand.

So then how do LS carriers work? Well they function on whats called torque applied, meaning the more pressure the engine places on the differential AND the more resistance both tires place back against that pressure will determine how strong the clutches grab as they hold the axles from spinning. Thats why they're called "limited" slip. So yes, this is also why a LS can still spin one tire if the ground is too loose or if one tire sits on solid ground while the other is sitting on gravel, etc.....

Now its also important to understand that OEM limited slip carriers are set static low so they have more friendly road manners in wet/slippery conditions but you can get aftermarket LS carriers that are set with so much static pressure that they're chatter the tires in turns. Most people are down on LS carriers because they dont know how they work and/or they've only felt the loose feel in OEM limited slip carriers.

Lastly, there are threads about how to check the clutch packs in your carrier for overall condition and possibly the ability to re-stack them so they're work better. Also, changing the fluid can rejuvenate a loose feeling LS, so thats always the first option when you think the differential isnt working right.

Oh yeah..... NEVER let a limited slip spin one tire because it can quickly destroy the clutch packs. They're very sensitive to wear and tear and even driving with two different tire sizes can ruin a LS carrier in around 10 miles.

 

Katoom already touched on this issue, but I will elaborate:

The factory stacking of the clutch in these trucks sets it up so most of the clutch pack does nothing. Performance is only negligibly better than an open diff. Restacking dramatically increases the number of friction surfaces that limit one wheel peel.

Also as far as initial static loading something else to consider is that the more torque that is applied, the more the spider gears deflect the side gears against the clutch packs. This is where MOST of the lockup comes from. Once you spin a one legger, the lack of traction limits the torque which can be applied, so obviously there are limitations.

Oh, and since the factory is stacked this way, most of the clutches/steels have been exposed to *ZERO* wear. But IIRC the factory pack is short one friction to stack the whole pack clutch/steel/clutch etc. and one friction *has* been exposed to wear, so some folks get a new friction set when they restack so they have enough to maximize the pack performance and toss the one friction that has been exposed to wear.

 

take it apart and restack the clutches ,they are not worn out!