A question of torque

[StevenA]

wasn't broke, so decided to fix it!

Wanted to check the condition of my diffs. After reading the workshop manual, took it all apart and then started the rebuild. First thing on the list the pinion bearing preload. As I don't have a dial torque wrench, decided to convert the required torque (1.5Nm) into an equivalent torque at the flange.

As the flange is 4cm (0.04m) from the pinion axe, 1.5 nm is equivalent to 38N at 4cm is equivalent to (aprox) 4kg pull. This seems a lot.

Then I thought of the swivels where the preload is 1.46kg at the track rod which is roughly three times the distance from the pivot point - ie about the same.

Can anyone confirm (or not) that a correctly set up diff pinion requires 4kg pull at a hole in the flange after stiction, or that a correctly set up pinion is very stiff when turned by hand? Seems very tight to me but then there are some pretty hefty forces against the ring.

BTW - the actual pull is around 0.5 kg, but thats after 100k miles so I would expect it to be lower.

Any help, answers or corrections to schoolboy physics appreciated.

[cipx2]

On one hand the math is right, 1.5 Nm is about 4 kg at 4 cm.

On the other hand, this is to be measured with the pinion oil seal removed.

BUT:

- on one leg, don't bother to adjust the preload without changing the bearing, it's not worth it, and don't do that if there was no oil leak, no noise and no play at the bearing

- on the other leg, check and adjust the backlash if necessary - that's the only thing worth doing if you have the tools (including a torque wrench).

[StevenA]

On one hand the math is right, 1.5 Nm is about 4 kg at 4 cm.

On the other hand, this is to be measured with the pinion oil seal removed.

BUT:

- on one leg, don't bother to adjust the preload without changing the bearing, it's not worth it, and don't do that if there was no oil leak, no noise and no play at the bearing

- on the other leg, check and adjust the backlash if necessary - that's the only thing worth doing if you have the tools (including a torque wrench).

Thanks for the confirmation.

I'm not sure that I would agree about not resetting the preload without changing the bearings - if its too low then it will accelerate wear on the ring and pinion - however I'm changing all the bearings this weekend so not an issue.

After talking with one of the rebuild shops, it seems that correctly set up diffs are really tight at the pinion, and so an indication of correct preload can be had even with the seal in (my seal was dragging max 0.5 kg as that was the total) as the total drag is so much.