09 2500HD 4wd engaged noise?

frased · March 6, 2019

Hey all been a while.

I have a new issue ONLY when I engage 4wd. Sounds like a humming noise.

I had my transfer case NQF out last year and it is mint. Fixed engagement fork. Installed fresh correct oil. Been using my 4wd without issues ever since.

what other components should I check? U joint?

I guess my thinking is the front axle is still spinning in 2wd so maybe it’s the transfer case after engagement. But it looked brand new when I had it apart last year.

also changed font axle gear oil last year.

Edited March 6, 2019 by frased

casey.mikl · March 6, 2019

There’s an actuator in the front diff that locks when 4wd is engaged

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frased · March 6, 2019

Ah yes forgot about that one! I actually swapped that out when I was originally having transfer case problem.

so I should focus on front axle gears or hub assembly (both sides) bearings?

U joints?

Edited March 6, 2019 by frased

davester · March 6, 2019

In 2wd, with the truck stopped/in park, can you reach under the truck and rotate the front driveshaft? You should be able to spin it freely.

If you can't spin it, then either the front actuator or something in the transfer case isn't working right.

frased · March 6, 2019

50 minutes ago, davester said:

In 2wd, with the truck stopped/in park, can you reach under the truck and rotate the front driveshaft? You should be able to spin it freely.

If you can't spin it, then either the front actuator or something in the transfer case isn't working right.

I’ll check that. I’m assuming it will be OK since in 2 Wheel Dr. I have no humming noise or anything. Only when I engage four-wheel-drive I hear humming coming from the four-wheel-drive system.

Anything else I should check while I’m under there?