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Discussion Starter · #1 ·
I have a poping noise under the motor when its in 4wd and only when im turning. i think its the differential and if so does anyone know where i can find one with 3:73 gears.
 

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2004 gmc
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Are you on pavement when you do this? If so, stop. Read the Owner's Manual. iIt says don't do it on pavement.

If that's the issue, it's normal driveline binding.

If you're sure you need a replacement front differential, look on Ebay, or www.car-parts.com for a junkyard nearby.
 

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+1, the front diff is a "locker" or welded. No limited slip to compensate for the different wheel speeds while turning.
It is not the left and right front wheels that are binding but the front and rear differential. When you are in 4X4 the front and rear diff. are spinning at the SAME speed and when you turn the wheel the speed of each differental tries to be different. Roadie has a great drawing of this (posted 50 or so times) and I hope he will post it for your enlightenment.
 

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+1, the front diff is a "locker" or welded. No limited slip to compensate for the different wheel speeds while turning.
Please explain the source of your stunning misinformation about our platform.

From an old post I find necessary to drag out every so often:

I posted in a similar thread, since this question comes up a dozen times every start of winter:

Yes, we have an open front differential. That means whether you're in a turn or going straight, the front wheels are allowed to turn at different RPMs. But they're not entirely free-wheeling because of the differential being engaged in A4WD, 4HI, and 4LO. The diff is going to spin at the AVERAGE of the left and right wheel's RPMs. And through the gear ratio of the ring and pinion gear, it will drive the shaft from the transfer case to the front diff at some lower RPM.

The transfer case is not a viscous coupling like some are. We have electrically driven clutch plates that the encoder motor commands to transfer a little or a lot of torque. In A4WD the clutch plates are prepositioned close to, but not engaging back to front until slippage is detected. Then the encoder motor moves the clutch plates closer together and transfers torque towards the front and that takes a short time and sometimes the torque arrives with a jolt.

When you're in 4HI or 4LO, the clutch plates are pushed far together to transfer maximum torque, or attempt to lock front to back. Since it's a clutch that can slip, it isn't a true locker front to back, but it is very close. It gets me up hills even when I have one front tire two feet in the air. It should be leaking out all the torque, but because of the attempt by the transfer case to do 50/50 split of torque, it can't all go forwards. Some goes to the rear, the G80 locker shares it side to side, and progress is possible.

Now to the crow-hop phenomenon in 4HI and 4LO. I've posted on this before. Every six months or so. That effect of driveline bind-up is caused by the different LENGTHS that the front and rear differential are tracing out as you go through a turn. The front diff is AVERAGING the RPMs of the front wheels, the rear diff AVERAGES the RPMs of the rear wheels, but in a tight turn the front and rear diffs are a different distance from the turning point, which is in line with the rear axle. Here are the numbers:



With an almost locked transfer case (with 50/50 torque sharing), the driveline will bind up and sooner or later either a wheel will hop to relieve the stress, or a CV joint will pop. Don't do this on dry pavement.
 
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