06 Trailblazer with bad front differential

[Augdog74]

My wife could smell something burning in the front of our trailblazer. Took it to the mechanic and they said the front differential is bad and will cost at least $2000 to replace! They think it is from the blazer being in 4-wheel or auto mode going down the highway. Does all of this sound right? Could there be anything else that could have caused this? I know I've told my wife not to use 4-wheel on the highway but she may have switched to auto... Bad day for me! Just looking for any helpful suggestions...Thanks

[MT-2500]

Originally Posted by Augdog74

My wife could smell something burning in the front of our trailblazer. Took it to the mechanic and they said the front differential is bad and will cost at least $2000 to replace! They think it is from the blazer being in 4-wheel or auto mode going down the highway. Does all of this sound right? Could there be anything else that could have caused this? I know I've told my wife not to use 4-wheel on the highway but she may have switched to auto... Bad day for me! Just looking for any helpful suggestions...Thanks

For Any suggestions we will need a lot more info.
Driving in 4W auto on dry payment is.
Not a good idea.
But.
Just a one time of leaving it in auto mode should not wipe out front end.
A Long drive in 4W on drive payment is not good on it.
Did it make any noise besides the smell?
A bad front end usually makes a noise.
I would be asking what the burning smell was and what all is bad on front end.
Did they just take a quick look at it and make a wild decision or tear it down and inspect it?

My best suggestion would be get a second opinion from a good repair shop.
What part did they say was bad?

[Schurkey]

Why should "4W auto" make any difference at all?

Weren't Trailblazer variants sold as AWD vehicles, that did not have a switchable front axle disconnect? (i.e., engaged ALL the time?)

[Augdog74]

Originally Posted by MT-2500

For Any suggestions we will need a lot more info.
Driving in 4W auto on dry payment is.
Not a good idea.
But.
Just a one time of leaving it in auto mode should not wipe out front end.
A Long drive in 4W on drive payment is not good on it.
Did it make any noise besides the smell?
A bad front end usually makes a noise.
I would be asking what the burning smell was and what all is bad on front end.
Did they just take a quick look at it and make a wild decision or tear it down and inspect it?

My best suggestion would be get a second opinion from a good repair shop.
What part did they say was bad?

I will definitely get a second opinion. No--there was not any noise. They did not tear it apart or anything. I believe they said the smell was the oil burning in the differential, maybe? This is a local mechanic that I trust, but I still think I will get a 2nd opinion, also.
Thanks!

[MT-2500]

Originally Posted by Augdog74

I will definitely get a second opinion. No--there was not any noise. They did not tear it apart or anything. I believe they said the smell was the oil burning in the differential, maybe? This is a local mechanic that I trust, but I still think I will get a 2nd opinion, also.
Thanks!

You are welcome
10-4 on second opinion.
Good Idea.
Let us know how it goes.

[MT-2500]

Originally Posted by Schurkey

Why should "4W auto" make any difference at all?

Weren't Trailblazer variants sold as AWD vehicles, that did not have a switchable front axle disconnect? (i.e., engaged ALL the time?)

The ones I have worked on are just selectable 4W drives.
The poster said he had a Auto 4W button.
With these they have drives choice of auto 4W and straight 4W and 2W selections.

The AWD drive cars and trucks are in 4W all time.
But no front and rear end lock in that hurts to drive on dry payment.

[maxwedge]

A4wd does not engage in the TB unless there is excessive rear wheel spin, then it locks in, it is ok to drive in A4wd on dry pavement. Yes get a second opinion for sure.

[jdmccright]

As mentioned, the Auto 4wd won't engage until the rear wheels start to spin. Just travelling down the highway, the truck works in 2wd...the front diff is (or should be) disengaged.

If the front were engaged, it would not be a critical factor going down a relatively straight highway. But she would definitely feel the truck be difficult to turn in more than slight curves on dry pavement, especially when travelling at low speeds.

A truck with AWD has a center limited slip differential to cope with a differing front and rear driveline speeds...regular 4wd has a simple transfer case that locks the front and rear together with no slippage when the Auto 4wd engages or 4HI is selected. AWD was only standard on the top of the line TB SS for 2006. The rest had the Auto 4wd or variants thereof.

All you'd have to do is remove the front diff plug and to a dip test on the fluid, dab it and sniff it to see if it is the smell you experienced.

[Schurkey]

I learn something new every day.

I'd have sworn that when I turn my '03 Trailblazer's knob to A4wd, that the front axle actuator engages. The transfer case does not power the front axle until there's a difference in speed between front wheels and rear wheels, and then the transfer case clutch is engaged so that it sends power to the already-engaged front axle. The difference, then, between "engaged" 4WD and "cruising on 2WD but ready for 4WD" is controlled by the transfer case clutch via the body computer.

Apparently I'm wrong.

At any rate, the AWD versions of the Trailblazer-style vehicle did not have a disengageable front axle actuator. One would think that if the front axle can't be disengaged, that the differential would be built to accept the loads and motions involved in having the axle engaged full-time. Therefore it's unlikely that damage was done to the differential by the original poster driving in AWD. (or do the AWD versions of the Trailblazer/Envoy use a different front differential from the 4wd versions???)

Of course, anything can break--so it's not impossible that the front differential is toast even if it was designed to accept loads from being engaged on dry pavement at highway speed. For all we know there's a leaking seal and no fluid in the differential...