Front Differential trouble shooting?

[06Z71guy]

About a year ago, I took my 2006 Z71 in for a thorough look over by a respected mechanic. I had just bought the truck, used w/ 175k on it. He told me the transfercase had almost no oil in it and metal shavings came out. After a lot of research I bought a remanufactured unit from a shop in Baltimore. G.M. Transfer cases is pretty much all they do. Great warrenty. After having it installed, the truck had a bit of a rubbing sound. Louder at low speeds, and with increase in speed, the pitch went higher and eventually was undectable. This was in 2WD. In 4WD the noise and rubbing became more intense. The initial though was "bad transfer case". Made sense. However, the noise wasn't God awful and I only used the truck on weekends. As the year went by, the noise became more apparent. Since I love the truck, and the miles were getting up there, I decided to start replacing items that may be the source of the noise, as well as being proactive. Front hubs, and drive axels replaced. Drive shaft to the rear differential as well as U joints. Noise, rubbing still there. I had the transfer case sent back. They found some slighlty higher wear on the bearing than they thought it should have, so they overhauled it again. New chain, bearings and seals. My question...is there a way to troublshoot the front differentiual BEFORE I re-install the transfer case? Just trying to be efficint at this point. BTW, transmission has been shifting smoothly and no codes. I was also thinking the electric encoder may be the issue if it's "partially" enaged or disengaged..if thats even possible, as it controls either 2WD or 4WD operation in the front differential.

Any thoughts?

 

[EXT4ME]

Quickest way to check the front differential would be to change the gear oil.

Remove the fill plug first and then remove the drain plug.

Check the magnet on the drain plug.

You would usually find SOME metal on the magnet, but it you find what you think is a lot, it may be time for a rebuild.

Either way, a fresh lube change would not be a bad thing.

 

[Auto Parts Guy]

Spin the flange of the diff by hand and listen for any noises since the front driveshaft is out. Could be a bad pinion bearing. The front shaft on the NP246 case spins in 2wd so makes sense noise could be there in 2wd and 4wd.

 

[06Z71guy]

Spin the flange of the diff by hand and listen for any noises since the front driveshaft is out. Could be a bad pinion bearing. The front shaft on the NP246 case spins in 2wd so makes sense noise could be there in 2wd and 4wd.

Thanks! They sent back a different unit, so fingers crossed. The shop does do several checks of the units, on spin machines to ensure the bearings are good... however without a full, realistics load on the case, some defects are not as audible. They use some type of fluid resistance machine to simulate a load, but they admit, it's not the equivilent. Also replacing the entire drive shaft, u joints etc...

 

[06Z71guy]

well, it wasnt the transfer case....or the drive shaft, or the front hubs or CV Axles...

im so tired...and upside down in the deal. Is the 4wd selection supposed to be a quiet and smooth operation when engaged?

 

[Auto Parts Guy]

It is not supposed to make crazy noises while in 4wd assuming you aren't driving on pavement. You can hear the front diff motor engage and the t-case engage, but that should be about it.

My front diff pinion bearing went out and had very similar symptoms as yours. Did you check the front diff? Spin the flange by hand?

 

[06Z71guy]

It is not supposed to make crazy noises while in 4wd assuming you aren't driving on pavement. You can hear the front diff motor engage and the t-case engage, but that should be about it.

My front diff pinion bearing went out and had very similar symptoms as yours. Did you check the front diff? Spin the flange by hand?

I was not thee when it was "checked" but I suspect it was not properly checked. I am on dry pavement when I engage it for a moment or two, but its sounds like a growl from under me seat when I do. I may as well replace or rebuild the front diff at this point. It's only money, right?

 

[Auto Parts Guy]

If you have access to the truck, removed the four 11mm bolts holding the front driveshaft to the diff and spin the diff flange. Should be able to do it in about 5min or less and at least you know if it's the diff or not.

 

[06Z71guy]

If you have access to the truck, removed the four 11mm bolts holding the front driveshaft to the diff and spin the diff flange. Should be able to do it in about 5min or less and at least you know if it's the diff or not.

thank you. the truck is back...and I'll check it out this weekend. makes sense.

 

[redheadedrod]

How old are the tires on your truck? Mine made a lot of noise because the tires were not perfectly the same. I went to new tires and the sound went away right away. I felt for sure there was something major wrong. It howled pretty good when in 4wd and quiet when in 2wd. Swapped out the tires and was a lot quieter.

 

[06Z71guy]

Just a

How old are the tires on your truck? Mine made a lot of noise because the tires were not perfectly the same. I went to new tires and the sound went away right away. I felt for sure there was something major wrong. It howled pretty good when in 4wd and quiet when in 2wd. Swapped out the tires and was a lot quieter.

Just 1 year old, and under 5k miles on them. Thx.

 

[06Z71guy]

easy

thank you. the truck is back...and I'll check it out this weekend. makes sense.

Easy enough. Disconnected the front diff...it turned freely, but of course with no load or resistance, and not at any kind of speed. The front end was up on jacks, truck in neutral so I was able to rotate each front wheel with a bit of speed...nothing. Hubs and axels seem good. Recently replaced. It's possible its the rear diff as noise and vibrations travel under the vehicle,and perhaps even a defective tire.