Hey guys. I've got a 2000 Suburban and when I put it in 4 and accelerate, I get a clicking/rubbing sound from the front end. It only happens in 4 and not when coasting or braking. Turning does not make it better or worse. It happens when driving perfectly straight. I'm attaching a picture of the oil that seems to be leaking on the passenger side where the CV meets the diff. The CV feels tight but I don't know if the fact that I was in park in 4wd when I checked would affect that. Is this a bad CV? Bad U joint? Other possibilities?

 

The oil leak will be the output seal of the front dif....The half section can be removed and repaired while leaving the rest of the dif in place.
hard to say what the clicking noise would be but if you say it makes the noise while going straight I would take a guess at the front prop shaft ujoints...best way to know for sure is to drive in 4x4 on hoist or on jack stands

 

I went and tested the u joints and they're tight. I noticed that I could deflect the axle flange on the drivers side by a few millimeters side to side. There seems to be some play in the diff. Between that and the leak on the diff seal that you correctly pointed out, I'm starting to wonder if theres something bigger going on in the differential.

On a related note, is the front diff supposed to lock in low range? If so, I definitely have a problem up there because it's not locked in 4 low

 

it won't go into 4low unless the trans is shifted to neutral
the leak is a front axle seal
are all the tires the same brand and size?

 

Yeah, I know that. It was in 4 low but the two front tires could soon at different speeds. I was asking if that was normal.

Yep. Same tires, same rims, rotated every 3000, alignment every 12000 diff fluid every 24000

 

no lock on the front diff if that's what yr asking

 

Well that's good to know. Still need to nail down that noise