Talk to Dr. Diff. You'll see on his website that he no longer carries the Eaton Truetrac due to quality issues.

I bought one several years ago, and it was junk. From what I could find it seemed to only be a problem with the MOPAR 8 3/4 version.
It's been a while, but I'm pretty sure the problem was with end play in the side gears. They're supposed to be a tight fit in the case, but the one I got had 0.045" end play in one of the side gears. That means that gear would be constantly banging back-and-forth by 0.045" every time you accelerated or decelerated.
I bought one of Dr. Diff's proprietary units, the Sure-Trac II. As I recall, (check with him to see if I recall correctly ) he makes them from Ford 9 inch units, which he orders unfinished and machines them to fit 8 3/4 bearings and ring gears.
Here is the link that was provided above by 83hurstguy:
https://www.doctordiff.com/8-3-4-helical-gear-sure-grip-sure-trac.html
Bottom line, I definitely do not recommend the Eaton Truetrac.

Robert

Last edited by rftroy; 06/15/23 12:57 AM.
AAR 4-speed 3.91, Tor-Red;
70 440 6 pack Roadrunner 4-speed 3.54, Plum Crazy;
68 Formula S conv 383 4-speed 3.23, Electric Blue;
69 Barracuda conv Slant 6 OD4 2.94, 71 B5 Blue;
78 Lil' Red Truck, Red;
70 Challenger S/E. 505 6 pack, Passon 5-speed, 3.55, B7 Blue