Offroad Trailblazers and Envoys

A little diagnostic help.

Trailblazer and Envoy related, but not off-road related...

by ClayPerrine » Sun Jan 22, 2023 6:22 pm

Hello all.
I am somewhat new to owning a 2006 GMC Envoy SLT, so I am asking for diagnostic help. I am a professional mechanic, specializing in vintage Porsche and BMW vehicles. So while I know a lot about cars, I don't know a lot about my GMC Envoy.

A little background on the Envoy.

My parents bought it new from the dealer after their Olds Bravada was hit and totaled on a trip. They were pulling a car trailer with a vintage Chevy on it, so the Envoy has been a tow vehicle since the day it rolled off the dealer lot.

I inherited it and the trailer after my father passed away in 2020. Before then I split the maintenance and use of the Envoy and trailer with him so I could haul my vintage Porsches.

In 2019 the Envoy ate the transmission in North Carolina while on a trip. I had the transmission replaced by the dealer in Boone, NC. It has run well ever since. Recently it started making a noise that I can't quite identify. From somewhere in the front, it makes what I can only describe as a honking noise. Not a horn honk, more like a goose honking. It only happens when the Envoy is moving, and it is intermittent.

I just got through checking things, and the front differential was very low on fluid, and appears to be leaking. I topped it up and drove it again. The noise is still there. At this time I am suspecting a bearing going out in the front differential, but I want to be sure about it.

Is it possible it is the 4WD Disconnect? Or should I focus on the diff? I don't like the fact the diff was very low on fluid, so that is the direction I am leaning at this point.

If it is the differential, would it be easier to just replace it rather than trying to fix it? I have a trip in March, and I need the Envoy fixed to pull the trailer.

Thank you in advance.

Clay Perrine

74 Porsche 914 1.8L "Froderick" (Severely injured, but he will be back)
73 Porsche 914 4.0L Six "Igor" (The big scary 4.0L monster six)
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06 GMC Envoy SLT
Clay Perrine
74 Porsche 914 1.8L "Froderick"
73 Porsche 914 4.0L Six "Igor"
70 Porsche 914-6 "Elwood"
95 BMW 540i "Inga"
06 GMC Envoy SLT
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by DirtyBacon04 » Wed Jan 25, 2023 6:14 pm

I don't have much experience with my TB goose honking at me and I've gone through 3 front diffs. Diff issues are usually a grinding noise and are consistent instead of intermittent. I'd go ahead and pull the splined disconnect and clean and regrease anyway, if you've never done it.

As far as the honking goes, might want to look towards wheel hubs. Find the speed it's making the noise (slower the better), then veer truck left to right listening to to the wheels. If the noise goes away when you swerve left, then your front left wheel hub is likely bad. Same idea for when you veer right.
If there's no detectable, repeating pattern to the noise and it's kinda just random, I would think suspension related. Checking all control arm bushings, ball joints, etc.
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by bartonmd » Wed Jan 25, 2023 8:05 pm

I'd look at things like upper strut bushings or sway bar end links if it's just when you hit bumps. Likely not a diff from what you're saying.

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