Thrust arm torque/preload. Rear on ramps vs jack under diff?

[Gene in NC]

Thrust arm torque/preload. Rear on ramps vs jack under diff?

If car is correctly preloaded, front wheels on ramps and car is level, how can front suspension tell the difference between rear on wheels on second set of ramps vs jack under the differential. By definition the center of the diff is on centerline of rear tires.

If front suspension can't tell the diff, why not just jack the diff to level the car before torqueing the thrust arms?

[Zeuk in Oz]

Thrust arm torque/preload. Rear on ramps vs jack under diff?

If car is correctly preloaded, front wheels on ramps and car is level, how can front suspension tell the difference between rear on wheels on second set of ramps vs jack under the differential. By definition the center of the diff is on centerline of rear tires.

If front suspension can't tell the diff, why not just jack the diff to level the car before torqueing the thrust arms?

If I understand your question correctly, you are suggesting that you have already pre-loaded your car with cement bags or such as I hope you are not suggesting having people sitting in your car and having it up on a rear diff jack.
Apart from the difficulty getting the same angle on the front suspension as though the rear wheels were on the ground, the thing that would worry me most is crawling under a car on a rear diff jack.
I would suggest you find a slope somewhere where you can drive onto front jacks and the car is then level - much safer as long as you chock the wheels etc.

[Bellicose Right Winger]

Jacking or rear on ramps makes no difference. As long as front is on ramps, and car was driven onto ramps, you're good to tighten thrust arms. Making car level by jacking rear of car or putting rear on ramps has a very minor effect on load on front wheels.

Paul Shovestul

Thrust arm torque/preload. Rear on ramps vs jack under diff?

If car is correctly preloaded, front wheels on ramps and car is level, how can front suspension tell the difference between rear on wheels on second set of ramps vs jack under the differential. By definition the center of the diff is on centerline of rear tires.

If front suspension can't tell the diff, why not just jack the diff to level the car before torqueing the thrust arms?