Auto 4 Wheel Drive Bucking at Low Speed

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S33k3r

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When I am cruising a parking lot at low speed and turn, my Suburban begins bucking. This seems to only happen in auto 4 wheel drive; 2 wheel high works just fine.

Anyone experience this before?
 
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S33k3r

S33k3r

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Tested a bit further... It won't go into 4 wheel low, at all. 4 Wheel high seems to work, as does 2 wheel high. It will select auto, but bucks when I am going low speed. Anyone have any idea what this might be? I have no alerts in the DIC.
 

swathdiver

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When I first got my truck the fluids were all original, truck acted like it wanted to go in two different directions. Changed the fluids and all was good.

These trucks don't like to turn in 4WD on hard ground, especially pavement.

4LO engages by first stopping or going under 3mph, shifting to neutral and then place the selector to 4LO. In seconds it will engage, you'll feel it, then you can put it back into gear. If you're engaging 4LO while in gear, you'll eventually break it. Max speed in 4LO in my GMT900 is 39mph.

Do you have access to a computer scanner like a Tech2?
 

PG01

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Like james said, stay out of 4wd on dry pvmt... auto locks hubs, for lack of a better term, and once it senses slip it engages front diff.... again like james said it is 'shift on the fly' for auto through 4hi.... i always put it in neutral and while rolling way below 5 mph shift into 4 low
 
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S33k3r

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When it bucked last night, I was in auto mode, in a parking lot and barely moving. When I tried to manually place it in 4lo this morning, I was in park. I guess I'll dig through the owner's manual to correct my understanding on how it is supposed to work.

As an aside, I had the fluid in both differentials changed approximately 3 weeks ago, and am 99% sure my mechanic used the right fluid (he's honest, and I told him EXACTLY which kind to use.

And thank you for your kind answers. I am new to 4 wheel drive, but am soaking up as much as I can about it. Spent the last few weeks boning up on Quadrasteer...
 
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swathdiver

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It seems to me you have something amiss in your transfer case.

Don't put it in 4LO in park, neutral only says the manual. I did that once on my truck during the test drive in my ignorance and it protested violently!
 

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