Eaton recommends a petroleum/mineral based GL-5 80W90 gear oil for all Truetrac differentials. Do not use synthetic gear oil or friction modifiers.
 
Eaton Detroit Truetrac Diff 31  Spline 
 
Differential is made for an 9" rearend only
 
This differential will work with a 2.891 or a 3.062
 
3.00 gear ratios & up 
 
 
The Detroit Truetrac was the first helical gear differential ever introduced into the automotive aftermarket as an Eaton brand. It remains the leading helical gear-type limited slip differential in the industry. Detroit Truetrac's proven helical gear design eliminates the need for wearable parts, resulting in maintenance free traction recognized not only for its toughness, but its smooth and quiet operation as well.Proven design, low cost and effective performance all make the Detroit Truetrac limited slip differential the ideal choice for a wide variety of vehicle applications. No maintenance - Just Traction.
 
TUReat913A586