The weakest link in a Dana 80 is the spider gears.
They are the same size as used in the Dana 60 & 70.
With an 80 open carrier, you only have 2, and a limited slip, you have 4.
Dodge used 2 different types of limited slip units in the 80.
The Trac-Lok, and the Powr-Lok.
Comparing the 2 side by side, you would think the Trac-Lok would be the better of the 2 because of all the extra clutch plates and discs.
But unfortunatley, the way they are stacked defeates their purpose.
Starting with 5 plates, then 3 discs makes only 1 surface contact area between 8 of them, then alternatley stack the remaining few with 1 dished disc for preload.
The plates and discs are all flat and are not suppose to be restacked.
A Powr-Lok uses dished discs, flat plates, and use less per side.
They can be arranged for different preloads with instructions right out of a Dana manual.
Plus the spiders are mounted on a 2 piece cross shaft that allows them to add preload under torque, to apply extra pressure to the clutch pack, makeing them less likely to slip.
The Trac-Lok spiders are on a 1 piece fixed cross shaft, and cannot apply any extra pressure to the clutch packs.
The reason this is important is because any torque that is going through the spiders to the opposite side is what breaks them.
You want the clutches to take the torque load, and take it evenly, reduceing the strain on the spiders.
With that l o n g explaination out of the way, 90% of the Dana 80's have a Trac-Lok.
An upgrade would be to go to a Powr-Lok.
Or, depending on how the truck is used, go with a Detroit Locker.
No spider gears at all in a Detroit.
Another, but not as necessary, would be to go to 37 spline axles shafts.
Would really have to be under abuse to mod the shafts, but they do break.
Sorry for such a long post guys.
Hope this helps.
Brad
