How do I test the front differential?

[Mark_BC]

I need to swap out my whole front diff because it is 4.1 but I put 4.3 in the rear. I really should do this swap since I'm planning a trip over the holidays. I have the "new" 4.3 one which is in pretty good shape but it would be nice to be able to test it before putting it in. Do I just need to put a vacuum on some hoses? Or is it highly likely to work so I shouldn't worry about it?

 

[phattyduck]

What do you want to test about it? Without opening it up, you can't really tell much about it without installing it and putting it under load.

Unless you want to make sure it is a 4.3 diff - in which case, you can either apply vacuum or manually move the ADD collar. You'd still need axles in both sides to count revolutions...

-Charlie

 

[Mark_BC]

I want to test the ADD. I already checked the 4.3 ratio which actually is a little concerning since I just turned the driveshaft and watched the things inside the CV ports turn. But I understand that normally the shaft shouldn't turn the CV's unless vacuum is applied, correct?

Basically, I'd want to confirm that vacuum / no vacuum causes he correct engagement of the driveshaft.

 

[phattyduck]

The ADD actuator is swapable on the truck... So even if it is broken, you can swap your current one in easily. But yeah, you need to apply vacuum to one of the two ports. I couldn't tell you which one through - just try both.

-Charlie

 

[TheDurk]

When in doubt, RTFM: