2001 sierra 1500 Tcase sounds?

[jefferwin55]

Hey guys,

 

I had some bearings go in my NP246 so i had it re bearinged/sealed. Installed the Tcase last night and took her for a test drive. Theres a noise coming from the bottom of the truck (tcase?) that almost sounds like when you have the back tires on jack stands and run them without any ground friction. The sound revs up with the engine when in first gear but disappears when it shifts to second. Do new bearings need to break in? Or maybe its just that the autotrac oil hasnt penetrated everywhere in the tcase yet?

Any ideas?

 

Thanks!

[BIKEBUILDER]

Check universal joints before and after Tcase as well as bearings in front axle

[jefferwin55]

I lost a damn bolt for the front driveshaft so its currently no installed. Could it just be louder from the resonating sounds in the Tcase since the front driveshaft isnt installed? Checked the ujoints on the rear and they're still good. Its has a 7" lift so it eats through ujoints pretty fast though. I did axle seals all around last week too and checked the axles for play and they're tight and no metal filings at all!

[NSFW]

Might be a good idea to invest in a couple of these for your truck. You wont go thru u-joints and it wont be as rough on that magnesium case.

 

Those are Rough-country. But there's many types.

Troubleshootin time.

Fire it up, Shift the truck into 4low, roll foreward. hear noise?

Engage park brake,
Shift the t-case into neutral with engine running.

cycle to 1st and observe, shift to 2nd and observe.
Leave the transmission in gear and turn the truck off when done.
Now shift the case back into gear.

Did it still make the noise.

Isolating the sound from t-case or t-mission.

Double Check the oil level in your Transmission, HOT.
Check to ensure the t-case is sealed to the transmission and not dripping.
Verify the fluid level in the t-case.

NP8. Dex2 (smurf blood) NOT Dex4 or 5 or mercon.. will destroy the clutch in the case like right now. All the rest, dex 5 is okay, its that NP8 thats the odd-ball of the bunch.

note* The 4L60e does NOT like running without sufficient oil. Too little and it acts the crazy... too much and it shifts like a semi truck. Not enough will starve the pump, too much and fluid will airate due to the components splashing in the oil. The 4LXXe is royalty.

I don't doubt you got the inside clean and clear of any debris before you put it back together, so I'm confident.

My thoughts are that I can't think of anything that would make that kind of noise but only in one gear that would be t-case related. Transmission yea.
If it was the t-case you would hear the noise in all gears, and reverse as its all going thru the case on the way to the axles. Specific gears (like 1st) is a transmission related problem.

BUT 90% of the time with the 4L's its a fluid level issue, and not anything serious. WHen the t-case comes off, the transmission burps fluid... half a quart. Which is enough to cause problems in the trans.

The wierdest crap ever to happen to me is I lost a couple bearings out of the 4wd engagement thow plate, that sits between the encoder lever and the clutch-pack. No idea where they went.
T-case ate em. Never found em.

Good luck bro.

[jefferwin55]

Thanks for the reply! The sound is only happening in first gear regardless of if im in 4x4. And when i start my truck in second gear, it doesnt happen either so im assuming its something in the tranny Checked the fluid too after a 45 minute drive and its right in the middle of the full indicator so not enough dex isnt the issue. Im gonna bring it to a local driveline shop and they can diagnose it. The snow started falling up here in Canada so its time to get this figured out!