The Track-lock can handle only 400HP?? If that's the case, why would the factory put it behind a 71 Hemi at 425HP?

Thanks much to all of you who commented. I feel much better now. The funky numbers on the axle had me wondering if I had been taken 20 years ago when I bought this thing. I obviously didn't know enough about Danas back then to ask the right questions, and those numbers, especially the lack of the usual BOM numbers, gave me concern in the here and now. But now that I've cracked it open, and you guys have confirmed it's the real deal, well, all is good now.

Thanks again.

No. The switch over was above 4.10. 4.10 still used standard carrier. 4.56 needed the spacer or different carrier.

The 1971 Dana Track Lok is not the first choice for me. My 1971 Hemi Challenger exploded the 456 factory unit about with in a year once slicks were used. I have a 1970 B Body unit in the Challenger since 1972 with 538s not one problem with it and car turned high 9s with a 321 first gear Hemi Crash box 4 speed.If everything looks clean and correct put the dana in your car just be aware if you are hooking hard with good tires that there is a good chance that Track Lok could give you problems in the future. You got the Dana rear end so put it in your car, every Hemi deserves a Dana behind it.

Could be true, but for all we know the 4.10 gears that are in it NOW were not the driving factor for the lack of BOM numbers on the axle from 50 years ago. The statement from the service manual is still a possible explanation for the lack of BOM numbers on this axle.

Is true, not could be. Look at the options available from purchase books. Look at the Parts manual. You could get a 3.54 or a 4.10 gear. The Dana differential case supported both. The Race literature and the Dana documents support, along with anyone who has raced one or rebuilt them, that the switch over to a different case is 4.56. This gear has a much smaller pinion and the ring gear is required to move over about 1/4". They had a case with a thicker mounting flange, or racers would weld on a spacer plate to shift the ring gear over. The higher ratio was a a dealer available option, but only the carrier was changed with the gear, not the axle housing.

I know you want this to be a factory line part, but I think the wisdom is that production cars had Dana's with the known BOM numbers. Either 3.54, or 4.10. Getting a 4.10 did not require the axle housing to be changed or the differential carrier.

You have a Dana. Maybe some one knows what the BOM was if you bought a housing from a dealer. You number is more like a Dana part number then an assembly BOM.

Go to the spicer website and you can access the parts catalogs for the 68-78 Dana rears for Dodge/Plymouth, and the other manufactures that used it.

Now I feel like a dummy, didn't realize Danas had no clutch pack springs,Power-Lok 4 pinion gears Trac-Loc only 2 pinion gears,aside from having 4 pinion gears & a split carrier case what else would make a Power-Lok stronger if anything.

Twin vs single drive pin for one.