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Pungent Odor At 2500 Miles



I took my Avalanche and a new Travel Trailer on a shakedown cruise of about 1000 miles from Loveland, CO to Santa Fe, NM. ?One third of the way thru the trip my wife and I started getting this pungent odor in the passenger compartment whenever we stopped with a window open. ?We thought we had a propane leak from the trailer but we checked it out and it wasn't the trailer, as demonstrated by the fact that without the trailer we got the same smell.

Since my wife was getting nauseous from the smell, we took the Av into a Chevy dealer in Santa Fe to check it out. ?The service people smelled it as soon as I pulled in. ?They pressurized the fuel system and couldn't find any leaks. ?The Service Manager checked out Chevrolet's web site and found nothing. ?He called the factory and they didn't come up with anything.

The Service Manager, who was very sharp, then remembered a similar problem with the Tahoe. ?He said they had to change out the rear differential oil and replace it with a different type..he mentioned "grape". ?He decided to try that on my Avalanche. ?When they drained the differential oil I took a whiff..sure enough, that was the smell. ?He changed the oil, but told me that I should also take it to a dealer when I get home to get an extended vent tube put in as he didn't have the part. ?

Despite his good effort, the problem didn't go away by changing the oil. ?We now have this odor all the time and my garage reeks of it. ?I'm scheduled to see my dealer on Monday morning.

Now I'm really skeptical that this vent tube will fix it. ?It may deflect the odor in a different direction which might keep it out of the passenger compartment, but it's still going to vent to air and stink up my garage. ?In fact, everytime I stop somewhere you can smell it. ?It's particularly strong inside the driver's side rear storage compartment. ?(That's why a fuel leak was suspected.)

Since no one seems to have reported this problem before I'm afraid I could be in for a rough time in getting to the root of this. ?By the way, I have just over 3000 miles on the Av, it's a 2500/8100. ?My engine oil was changed out before I left for the trip.

If anyone has any good ideas I'd welcome them. ?I'll keep you posted on my adventure with the dealer on Monday.

I ran across this doing research for another topic - this is from the Mag-Hytek install:

GM Vent #1 - Hose Assembly Modification and
GM Install #2 - 1/4 in. Pipe Vent Hose fitting install

The GM 14 - 10.5 rear end has a problem. When the carrier bearings run in oil it.

The vent tube exit on the GM 14-10.5, 14-9.5, 10-8.5 is located on the

The GM 14- 10.5 rear end has a problem. When the carrier bearings run in oil it throws the oil up into the vent tube hole and in many cases will push the oil out and make a big mess on the under side of the truck. The GM fixes ar #1 try to run a longer hose up as high as possible and some times that will help. The Max oil capacity for this is 4 qts. of gear oil and that is the bottom line on the dipstick which is the bottom inside of the axle tube.

The GM #2 way is to drill and tap for a 1/4 in. pipe hose fitting in the axle tube between the spring and the pumpkin and install a barbed fitting for a 5/16 hose. Plug the old vent tube with a plastic cap (supplied). This works very well some folks may want to use a mechanic to drill and tap for the 1/4 pipe hose fitting. With this install it takes 5 qts. of oil and will take the oil up close to the top line on the dipstick which is the bottom of the axle. We recommend the #2 install.

BTW: I have seen references to the fact that the differential oil can be foul smelling - no personal experience. ;D
Thanks for the info on the differential problem. Based on my trip to the dealer today it may not be related to the differential at all. See my next post. I'm changing the name of this thread to "Pungent odor at 2500miles".
Well, today I took the Av into my local dealer. They were apparently quite familiar with the pungent odor problem. They said it happens on a lot of Chevy trucks and is caused by the undercoating burning off the exhaust system and/or brakes.

I was told the problem should resolve itself by about 5000 miles, and since I have just over 4000 I should have a better indication in about 1 month.

This diagnosis actually made more sense to me than the differential oil smell diagnosis. I was told that the reason the smell came on so strong, so quickly, is that it was aggravated by my heavy towing, which would make the exhaust system hotter.

What I don't get is why the Santa Fe Chevy dealer didn't come up with this!?

Am I getting the runaround, or does this make sense to anyone else? Has anyone else run into any such problem?