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‘02 Suburban 2500/‘08 Suburban 2500
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Discussion Starter · #1 ·
Probably not the best timing on my part to see if my new to me 95 Tahoe's 4x4 works :) but here's where I am at. Over the weekend dropped trans pan and replaced fluid/filter and shift solenoids and at the same time checked fluid levels in the center transfercase and front "diff"/gearbox.
  • Center transfercase was full, slowly backed the drain plug out and the fluid that seeped out was nice and clean.
  • Pulled fill plug from the top of the front diff/gearbox, stuck my finger in there and could not feel any fluid at all. 1.5QT of 80W90 later, it starts to seep out the hole and I can feel the fluid level with my finger. I'm not sure how long it has been like this, I have driven the truck about 5-600 miles and have never activated the 4x4.
Here is how I went to engage 4x4:
  • Slow to 1-2mph
  • Shift truck to neutral (N)
  • Pull 4x4 lever down to 4H
  • Shift truck to drive (D)
The video below is the gear whurrr/buzz I hear after going through the steps above.
  • Drive the truck and there is a speed sensitive buzz/whurr while driving.
  • ABS kicking in as I come to a stop 0:14 sec mark
  • Once I start going again, buzz/whurrr is gone
At no point is the 4x4 engaged, verified this by turning my wheel and looking out the window while sitting on 1-2" of packed snow/ice.

Thoughts!? :)
 

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Ok, try to find, on internet, a copy of your owner's manual. You should be able to shift into 4hi at any speed.
Gear noise in 4x4 gears is normal with the system we are using.

If you don't have working 4wd, I'd look at the front axle disconnect first. It is there to remove any unnecessary gear movement in the front diff. When a 4x4 gear is selected, this disconnect operates and connects the inner and outer axle halves, on the passenger side, together. In the mid 90's, G M went from a vacuum operated motor to an electric motor (it's actually a solenoid), I don't know which you have.
If you have the vacuum unit, there may be a leak. If you raise the hood, you should see a vacuum line going to the "motor" down near the right upper control arm.
 

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‘02 Suburban 2500/‘08 Suburban 2500
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Discussion Starter · #3 ·
Thanks RayVoy, so just for peace of mind, the noise I am hearing is normal? This is my first "real" 4x4 vehicle besides full time AWD Infiniti G35X, so a lot of these noises are new to me :).

The process of engaging 4x4 was from the owners manual. My initial thoughts were that for some reason I was moving too much or enough when I pulled the lever and that something was not fully engaged. I'll look into if I have vacuum or electric system
 

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I'm not familiar with that proceduure, to me, you are discribing the method of going into 4 low.

Could you possibly have locking hubs that require you to manually turn the lock?
 

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‘02 Suburban 2500/‘08 Suburban 2500
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Discussion Starter · #5 ·
I'm not familiar with that proceduure, to me, you are discribing the method of going into 4 low.

Could you possibly have locking hubs that require you to manually turn the lock?
I don't believe so, while replacing the ABS sensors I did not see anything that look like locking hubs that sometimes appear on early 90s Fords
 
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