Dana Super 70 Limited Slip Issues

[72k20Farmtruck]

Hi everyone, last weekend I rebuilt and swapped in a Dana Super 70 from a 2004 Express 3500 to my 1982 K20. The carrier I purchased was a power lock from East Coast Gear Supply for a 70HD. To use this carrier I had to shorten one of the axle shafts because the center pin from the Super 70 carrier was offset differently than the power lock unit.

The issue I'm having is after 3 days of driving, the diff is really binding up after I backup and turn, it's almost like the limited slip is locked up. I know what chirping feels like, pretty common in a new LS unit but this is pretty aggressive compared to what I've witnessed. The oil I used was master pro 70w-140 synthetic and two 4oz bottles of Spicer friction modifier. Shouldn't that be enough to prevent to clutches from binding? I am going to pop the cover off this weekend and try RedLine Shockproof Heavy. But I wanted to hook my peepers on that carrier and see if there's anything going on in there.

On the first drive with this set-up, everything was REALLY smooth and I was super pleased with it. Now I am upset. Any advice is welcomed, thanks.

I've included photos of the carrier, ring and pinion box, and the axle shaft I shortened.

[72k20Farmtruck]

Another thing I can throw in here is, turning after backing up feels like driving in 4wd on dry pavement. And no, my hubs are not locked.

[sweetk30]

Power-lok units can be set up to be easy -hard on clutch slip to the point its almost a spool or locker feel . I would call and ask them first.

[kwmech]

GL5 oil in the 85/90 range plus the modifier. It'll take a while to work itself in. I do have a concern on why the shaft had to be cut. Should not have had to do that.

[72k20Farmtruck]

Originally Posted by kwmech

GL5 oil in the 85/90 range plus the modifier. It'll take a while to work itself in. I do have a concern on why the shaft had to be cut. Should not have had to do that.

Ok maybe I need to just go for a long drive to get the oil moved around in there.

The reason for the cut shaft is this carrier is designed for a Dana 70HD, they didn't make a limited slip carrier for a Super 70. The main differences in a Super 70 and a 70HD is all standard dana 44,60,70, & 80's have 10 bolt holes in the cover. A super has 12, notice in the picture. The other main difference is the crosspin in the center of the carrier is offset like 3/8". So when installing an HD carrier, one axleshaft butts against the pin, the other sits a little shallow. So to get the best engagement possible, I used some Permatex Prussian Blue marking compound on the splines to see how deep it'd go. Then took the longer shaft and used it on the long side on the pumpkin, measured my flange difference, added an 1/8" for good measure and to prevent from being totally bottomed out. Then just cut it with a skinny wheel!

It's actually not uncommon to have to cut axleshafts down when modifying odd rear ends. My grandpa said they had to do that back in the day with 9" fords all the time because you never knew what you were going to get and you had to make it work.

[72k20Farmtruck]

Originally Posted by sweetk30

Power-lok units can be set up to be easy -hard on clutch slip to the point its almost a spool or locker feel . I would call and ask them first.

Ok I will give ECGS a call. Thank you.

[72k20Farmtruck]

Originally Posted by sweetk30

Power-lok units can be set up to be easy -hard on clutch slip to the point its almost a spool or locker feel . I would call and ask them first.

Talked to their tech, he told me clutches are probably still dry and need exercise. He said do a bunch of figure-8's to get that oil in there!

[kwmech]

Originally Posted by 72k20Farmtruck

Talked to their tech, he told me clutches are probably still dry and need exercise. He said do a bunch of figure-8's to get that oil in there!

Probably, but if the power-loc was assembled correctly the friction discs should have been soaked in the modifier prior to assy to keep them from sticking to the steels. Was the 140 wt GL-5 rated?

[72k20Farmtruck]

Originally Posted by kwmech

Probably, but if the power-loc was assembled correctly the friction discs should have been soaked in the modifier prior to assy to keep them from sticking to the steels. Was the 140 wt GL-5 rated?

I believe it was.