2007 Suburban Transfer Case Problem?

[marine_man]

I've got a 2007 New body style Suburban with 63k miles on it...

I developed a problem this morning that I'm trying to figure out... on my drive to work this morning I passed a vehicle, and on the deceleration from the pass I noticed a slight high speed shutter.. driveline related as far as I can tell. Thought it was odd, but it didn't continue so I brushed it off. About 10 miles later, while decelerating to a stop I got the shutter again. I took a left hand turn and felt something shift / slip. After making a hard right hand turn into the parking lot felt that same shift / slip again.

I took a look at my 4wd shift knob and saw that I was in fact in 2WD.. and for curiosity sake, turned the knob to the Auto 4wd mode.. which resulted in nothing happening... even after circling the parking lot, etc. The light for 2WD remained lit.

During my parking lot circling I noticed a slight growling noise.. almost like gears / splines were trying to engage, but weren't able to fully engage or disengage. I get the same noise in reverse in 2wd.

It will shift to 4wd, but I get a similar noise.

Is it possible that the Transfer Case shift solenoid (or whatever they use on this vehicle... familiar with my 96 K1500 more than I am with this vehicle) tried to shift partially and was unsuccessful, or failed and is trying to partially shift the transfer case?

The noise is definitely more pronounced in the front than the rear, and I'm pretty certain it's not a wheel bearing.

Any ideas / directions to look in?

Thanks!

marine_man

[marine_man]

I got a little more time to try and do a little more diagnosing...

I did get it to go into Auto 4wd... needed to be a little more patient. I can still get the growling noise on light acceleration / cornering. When I put it in reverse and back up I can hear a ratchet / clicking sound, but not continuous.. there's maybe a second or two between each noise while in reverse.

And perhaps the most telling, when I shift to 4 low I have very little tractive effort... the only change in speed I get (relative to the engine RPM's) is when the transmission shifts.. it's almost like there's a high amount of slip in the transfer case (both rear and forward wheels) when in 4 low.

Does that help at all? Any direction would be appreciated.

Thanks

marine_man

[ottertailguy]

I would take it to the dealer. Should be covered under the 5 year/100,000 miles transferable powertrain warranty.

[Jeremy airjer W]

Take a peak at the fluid. If it looks/smells burnt than........not good.

[marine_man]

Unfortunately I'm about 2 months past my powertrain warranty.

I pulled the top plug on the transfer case... and the fluid smells just fine to me... certainly not like anything burnt.

I did discover though that it's likely something electrical - I can hear the solenoids trying to shift the transfer case while backing up / driving forward.

Any idea where to start with troubleshooting? Is there a wire or wire(s) that I can probe to find out if it's getting the signal to shift from the controller behind the dash, or if it's something with the sensors on the transfer case itself?

Thanks!

marine_man

[Jeremy airjer W]

The encoder motors are popular failures. It is possible that it no longer sees that the motor is in the correct position and is trying to turn the motor to the 2WD position even though it already is. A scan tool woul be needed in order to see what the switch and the motor are saying to each other.

The fact that the fluid is good is a good sign!

[marine_man]

Is there a connector I can disconnect to keep it in 2wd?

[Jeremy airjer W]

I wouldn't unplug it under the car but you could try pulling the TREC fuse in the under hood fuse block.

[marine_man]

Well, the verdict is in... metal shavings on the transmission dipstick... I checked the transmission fluid about 2 weeks ago and didn't find anything them.. it must be getting progressively worse.

GM Says "they'll help me" with this repair.. we'll see.

marine_man

[marine_man]

Just got a call from the dealer... GM will cover except for a $500 deductible... new transmission will have a 3yr/36k mile warranty.

marine_man