Speed sensitive whine in 4WD

[NewfieEnvoy]

2007 Envoy 4WD

So I bought my Envoy about a month and a half ago with 6 months of powertrain remaining. So its time to get all the bugs worked out and get everything done under warranty that needs to be done. I had it into the dealer last week and they replaced the front diff seal and the rear seal on the transfer case. I now notice a speed sensitive whine coming from what sounds like the location of the TC, although I can't be sure it wasn't there before the vehicle is still new to me. However, I brought the truck in because the rear seal in the TC was leaking pretty bad.

So driving down a straight road in 2wd, turn off the radio and turn down the blower, then switch into 4hi you can plainly hear a whining noise coming from under the truck. Slow down or pick up speed (nothing above 60km/h in 4wd for me) and the whine will change pitch accordingly. Switch back to 2wd and goes away. The best way to describe it would be the sound of an airplane landing or taking off in the distance. Again its not terribly loud, with rain soaked roads you might not pick up on it with the road noise. There's no rumble/vibration or anything like that. My thing is I can't imagine the vehicle made this noise when it came off the lot, I wouldn't have bought a new truck that made this noise, as small as it is. I've owned several 4WD vehicles in the past (Ranger, Sierra, Pathfinder) and none ever made a sound like this. I know its not unusual to hear a little gear noise in 4wd, more moving parts, but it sounds like a bit more than that.

So after the seals were done and I noticed this sound I brought the truck back to the dealer and a mechanic took it for a run. I picked the vehicle up at the end of the day and the service provider said they couldn't hear anything at all, and to call in some day to schedule a manager come out for a road test with me. I don't think I'm out to lunch on this one but I want to make sure I'm well informed so I can get done what ever needs fixing. I read on another site it could be a bad bearing in the TC and that it maybe cheaper to replace the TC then a tear down and rebuild. What ever it is, I need this done before the power train warranty expires :-(

Any thoughts or help would be much appreciated,
Cheers, NewfieEnvoy

 

[The_Roadie]

There are many more parts that spin in 4HI mode than in 2HI, some in the transfer case and some in the front differential. If the rear TC seal was leaking, and nobody was checking the fluid level, then low fluid might have damaged something and I bet GM would LOVE to deny the warranty on that basis. How was the fluid level when the truck went in for the warranty work?

How they fix it is an economic decision they need to make, so it's not suitable for us to be giving advice. But at the very least get the noise noted on service records, and call GM zone management above the dealer if the local dealer denies there's a problem that you can clearly hear.

 

[n0kfb]

Did you get a receipt saying that you heard a noise while running in 4wd? If you did, it will help your case when something goes out just after the warranty expires. That said, the longer it is after the warranty expires, the less value your receipt has.

Good luck!

-- Dan Meyer

 

[NewfieEnvoy]

So the Envoy spent 3 days at the dealership and the problem has been resolved. They replaced four bearings, seals, and fluid in the transfer case. Now she's whisper quite. Glad to get it done under warranty :wootwoot:

 

[The_Roadie]

Thanks for the report, and good news about the cost.

Now don't forget now YOU own it, that the fluid change interval for the transfer case is a surprisingly short 50K miles. 100K for the diffs.

 

[NewfieEnvoy]

Thanks for the report, and good news about the cost.

Now don't forget now YOU own it, that the fluid change interval for the transfer case is a surprisingly short 50K miles. 100K for the diffs.

I'm very neurotic about maintenance, maybe I'll do it, maybe the garage will, but either way it will be done. This vehicle was a 4 year lease return that I just took possession of 4 months ago. It has 78K kilometers, so fairly low mileage but its a good time to get a jump start on any maintenance due. So I'm still working out all the details. Our winters are pretty gross around here and I don't have a garage so once the weather warms a little more I'll be going from one end to the other checking what needs to be done. I've already picked up a thermostat and if its a decent out on Saturday that will be going in, along with a TB clean.

Thanks to Roadie and all others here on the Nation I love my Envoy more than any other vehicle I've ever owned and its mainly because of this awesome support group. Its amazing knowing that there's nothing that can happen to my truck that someone here hasn't encountered before and can help out with.

 

[NewfieEnvoy]

I have about 2 weeks remaining of powertrain warranty so I put the truck into my local (very trustworthy) garage and asked them to do the full monty inspection, let me know everything you can find. Giving a garage the green light like that can mean big trouble, like opening a tab at the pub and then all your buddies walk in, oh no here we go. However, all good news, they couldn't find anything that needs attention except for one seal Looks like the rear output shaft seal in the transfer case is leaking again So that seal was done in January, then done again in April with a full TC rebuild, and now in May it needs to be done again
Anyone have an idea as to why this seal is just not working and possible solutions? My local garage says of course with out opening the transfer case their only speculating but they think the output shaft maybe scored, and its either not sealing or its tearing up the new seals. Sound reasonable? I'm worried about losing a TC outside warranty but at the same time I have 3 separate records in 6 months of this seal causing trouble, that's enough for me to raise all mighty hell for the next little while.