My 2014 Grand caravan has a reverse that is seriously underengineered. If you put it in reverse and try to back up a hill, like a nose down parking spot, it makes all kinds of weird jerky movements. Quite a few pages on the support site.
Getting back to rear wheel drive solid rear axle classics...Generally you want the trans and rear pinion on a net zero setting on acceleration. Let it be 0,0 or -2,+2. On general driving, you want it down a few degrees. These are static measurements at rest. Remember your measuring in relation to your trans angle.
Suspension Recommended Angle
Using Full Wolfe Race Craft Suspension - all solid mounting points. -1 to -1.5
Half Solid & Half Poly Mounting points -1.5- to -2.5
All Poly mounting points -2.5 to -3.5
All Rubber mounting points -3 to -4.5
The more you get away from having all solid mounting points the more the rearend is going to try and rotate upward during launch. Therefore the more angle you must start with to prevent the angle from becoming positive (+). The idea is that when the rearend rotates you want the angle between the driveshaft and the pinion would be 0.