How to inspect Q45 VLSD

[Lukaniuk]

I've just picked up a diff from a 91 Q45. This is my first experience with a LSD and I'm a little concerned about it:

 

1) Turning on either output takes a lot of force. I can do it by hand, but it is tough. A lot tougher than any of the open diff's seen - is this normal?

 

2) Looking at the diff it doesn't look like the drain or fill plugs, or any of the bolts on the cover have seen a wrench in years. When I opened the cover there was hardly any fluid.

 

Nothing looks irregular inside (I think), but I'm worried that this thing is toast. Is there anything I can do to give it a more thourough inspection?

[JMortensen]

When you turn the side gears in opposite directions, you're forcing them through the viscous fluid which is what makes the LSD work. It should feel difficult to turn. If you turn the pinion and it is hard to turn, then you may have a problem. You could pull the main caps off and remove the carrier and look at the bearings, but make sure you mark left and right and top and bottom and put the shims back in correctly. If the pinion moves smoothly I'd just install it and go for a test drive and see what it feels/sounds like.

Edited October 7, 2011 by JMortensen

[Lukaniuk]

When you turn the side gears in opposite directions, you're forcing them through the viscous fluid which is what makes the LSD work. It should feel difficult to turn. If you turn the pinion and it is hard to turn, then you may have a problem. You could pull the main caps off and remove the carrier and look at the bearings, but make sure you mark left and right and top and bottom and put the shims back in correctly. If the pinion moves smoothly I'd just install it and go for a test drive and see what it feels/sounds like.

 

Thanks. If I'm only turning 1 side gear does the diff act the same as if I'm turning both of them in opposite directions? Unless I'm missing something, it makes sense in my head that it would, and the pinion does move smoothly.