Got stuck ... why didn't the wheels spin?

[Bungee]

My Silverado is a 2000 4wd Z71 with stock suspension.

Took it offroad yesterday and got stuck in a mud bog. Let off the gas then applied power again--wheels wouldn't turn. Put it in 4Hi and 4Lo and gave the 5.3 all she got, but the wheels still didn't turn one bit. The tires are 285/75-16 Cooper A/T's.

The mud was up to the axles. Eventually got unstuck by building up traction under the tires in the mud with branches and large rocks.

The motor didn't rap or ping. It just felt like the tranny was slipping. Thought that was some kind of safety feature on these things. No? The tranny has new fluid in it, if that means anything.

As far as the motor, it runs really strong. But admittedly, I haven't run a compression check on it recently. It has 115,000 miles on it. I'm the second owner after 90,000 miles. The previous owner really babied it. I baby it as well.

This is the second time this has happened where the wheels would not budge. I'd like to know why the wheels didn't spin. Can anybody explain?

[kenny-1907]

I would say it is because of the tire size, stock gearing, and most likely the traction that was available in the sticky mud. the 285/75 from what i heard is the same in height as my 255/85 which is 33.3" tall when new. Approx 2" taller than the stock 265/75's This basically makes the gearing in the rear/front diff act like a higher gear. It is like trying to start out in 3rd or 4th gear on a 10 speed bike instead of 1st. In a situation like that i would say it would be very hard on the transmission. Also i do not think that it actually went into 4low, i have a 2000 as well and i can not get it to go into 4low from 4hi without having the truck moving apoprox 1-2 km's/h with the truck rolling. I don't think that the transfer case would shift into 4low from 4hi without the truck or at least the tires moving.

[kenny-1907]

Also without the tires moving like you said , how is it going to change gears in the transfer case.

[TexasF355F1]

You said it was stuck up to the axles. That could be a big reason too.

[kenny-1907]

Originally Posted by TexasF355F1

You said it was stuck up to the axles. That could be a big reason too.

I had my 88 K1500 jimmy with 33's and a 4" lift sitting on the body it was that stuck and it still spun them, but i also had 4:10 gears and posi front and rear

[norwood]

Originally posted by Bungee

Took it offroad yesterday and got stuck in a mud bog. Let off the gas then applied power again--wheels wouldn't turn. Put it in 4Hi and 4Lo and gave the 5.3 all she got, but the wheels still didn't turn one bit. The tires are 285/75-16 Cooper A/T's.

The mud was up to the axles. Eventually got unstuck by building up traction under the tires in the mud with branches and large rocks.

I'm a bit confused. You said the wheels weren't turning at all, but then you got unstuck by jamming stuff under the wheels for traction. So, the wheels must have been turning, right?

If your wheels actually weren't turning, you must not have had the transfer case engaged. You were in neutral so to speak. Barring any major drive component breakage that is. Which apparently you didn't have because you did get out. My '99 Silverado has to be stopped or going no more than 3 MPH and the tranny has to be in neutral in order to shift to 4LO. Just sounds to me like the transfer case wasn't engaged in gear.

[silveradoman]

I don´t have 4WD but I believe the transmission has to be in park or neutral for you to be able to go into 4LO.

[99redsilverado]

i think texas355f1 hit the nail on the head

[J-Ri]

I agree that the t-case must not have locked in. I have never been unable to spin the tires in ANY terrain. Usually I can spin them in 4x4 high in mud/dirt, but ALWAYS in 4x4 low. While pulling a pickup and dump bed trailer out of some sand I spun the tires in 4x4 low when I was on concrete.